Clinical SBAs
Clinical Infections Diseases: (111 questions)

Questions

• 1
  You are a GP. A 28-year-old female saw your colleague 5 days ago with pain and stinging on passing urine, for which he prescribed a three-day course of trimethoprim. The patient has returned today because she is no better. The midstream urine (MSU) from her previous visit has grown Escherichia coli resistant to trimethoprim, but sensitive to everything else on the report. What is the narrowest spectrum antimicrobial that you could prescribe for this woman?
  Difficulty: Hard     Topic: Common infections
  a

  cefalexin

  b

  amoxicillin

  c

  ciprofloxacin

  d

  penicillin V (phenoxymethylpenicillin)

  e

  trimethoprim
  Explanation: Amoxicillin is an aminopenicillin (broad-spectrum penicillin) with activity against E. coli. A. Cefalexin is an oral cephalosporin with a broader spectrum than amoxicillin. B. The correct answer. C. Ciprofloxacin is a fluoroquinolone with a broader spectrum than amoxicillin. D. E. coli is intrinsically resistant to penicillin V, and penicillin V will therefore never appear in a laboratory report for E. coli. E. The laboratory has reported that the isolate is resistant to trimethoprim.
• 2
  You are a GP. A 28-year-old female presents to you with a five-day history of severe pain and stinging on passing urine. She is otherwise well and has no fever or loin pain. A pregnancy test is negative. What is her diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Acute pyelonephritis (complicated UTI)

  b

  Gonorrhoea

  c

  Gastroenteritis

  d

  Cystitis (uncomplicated UTI)

  e

  Cyesis
  Explanation: Dysuria (pain and stinging on passing water) in a woman is highly suggestive of a urinary tract infection (UTI). She has no loin pain or systemic symtpoms, so we can conclude that it is an uncomplicated UTI (cystitis). A. She has no features of a complicated UTI (e.g., fever or loin pain). B. Gonorrhoea in women is usually asymptomatic, but may present with a vaginal discharge. C. Gastroenteritis presents with cramping abdominal pain, vomiting and diarrhoea. D. The correct answer. E. The pregnancy test is negative. Pregnancy presents with amenorrhoea and a gravid uterus.
• 3
  You are a GP. A 28-year-old female presents to you with a five-day history of slight stinging on passing urine. She has a fever and right-sided loin pain. A pregnancy test is negative. What is the diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Acute pyelonephritis (complicated UTI)

  b

  Gonorrhoea

  c

  Gastroenteritis

  d

  Cystitis (uncomplicated UTI)

  e

  Cyesis
  Explanation: The combination of urinary (dysuria) and systemic symptoms suggests pyelonephritis (complicated UTI). A. The correct answer. B. Gonorrhoea in women is usually asymptomatic, but may present with a vaginal discharge. Gonorhoea urethritis is uncommon in women. C. Gastroenteritis presents with cramping abdominal pain, vomiting and diarrhoea. D. She has systemic symptoms (fever) and loin pain (renal angle pain), which means this UTI is complicated. E. The pregnancy test is negative. Pregnancy presents with amenorrhoea and a gravid uterus.
• 4
  You are a GP. A 28-year-old female presents to you with a five-day history of severe pain and stinging on passing urine. The last time this happened was 3 years ago. She is otherwise well and has no fever or loin pain. She is not pregnant. What would you do next?
  Difficulty: Medium     Topic: Common infections
  a

  Ask for a urine dipstick.

  b

  Offer her ibuprofen for relief of symptoms.

  c

  Send a midstream urine sample (MSU) and offer a prescription for nitrofurantoin if the MSU is positive.

  d

  Advise her to drink a minimum of a litre of cranberry juice every day until symptoms subside.

  e

  Offer three days of trimethoprim.
  Explanation: This woman has cystitis with severe symptoms. A. The 2009 UK NICE clinical knowledge summary recommends antibiotics for all women with severe symptoms regardless of dipstick result. Antibiotics reduce symptoms on average by one day. B. Ibuprofen can be recommended for the relief of symptoms if required, but she should still be offered antibiotics. C. There is no need to send an MSU in uncomplicated urinary tract infection. An MSU is sent only if the patient is not responding to antibiotics, if the infection is complicated, or the infections are recurrent. D. There is no evidence for the use of cranberry products in treating UTIs (Cochrane review 1998). They are not harmful, but are probably no more effective then drinking water. E. The correct answer.
• 5
  You are a GP. A 28-year-old female presents to you with a five-day history of slight stinging on passing urine. The last time this happened was 3 years ago. She is otherwise well and has no fever or loin pain. She is not pregnant. What would you do next?
  Difficulty: Medium     Topic: Common infections
  a

  Ask for a urine dipstick.

  b

  Offer her ibuprofen for relief of symptoms.

  c

  Send a midstream urine sample (MSU) and offer a prescription for nitrofurantoin if the MSU is positive.

  d

  Advise her to drink a minimum of a litre of cranberry juice every day until symptoms subside.

  e

  Offer three days of trimethoprim.
  Explanation: This woman has cystitis with mild symptoms. The 2009 UK NICE clinical knowledge summary recommends a urine dipstick to guide treatment in women with mild symptoms. If the dipstick is negative for nitrites and blood and leucocytes, then you should not offer an antibiotic or offer a delayed prescription for antibiotics. Offer treatment if the dipstick is positive. A. The correct answer. B. Ibuprofen is helpful in relieving symptoms, but you still need a urine dipstick to decide whether to prescribe antibiotics. C. There is no need to send an MSU in uncomplicated urinary tract infection. An MSU is sent only if the patient is not responding to antibiotics, if the infection is complicated, or the infections are recurrent. D. There is no evidence for the use of cranberry products in treating UTIs (Cochrane review 1998). They are not harmful, but are probably no more effective then drinking water. E. You need the results of the urine dipstick first to decide whether to offer treatment.
• 6
  You are a GP. A 28-year-old female presents to you with a five-day history of slight stinging on passing urine. The last time this happened was 3 years ago. She is otherwise well and has no fever or loin pain. She is 28-weeks pregnant. What would you do next?
  Difficulty: Medium     Topic: Common infections
  a

  Ask for a urine dipstick.

  b

  Offer her ibuprofen for relief of symptoms.

  c

  Send a midstream urine sample (MSU) and offer a prescription for nitrofurantoin if the MSU is positive.

  d

  Advise her to drink a minimum of a litre of cranberry juice every day until symptoms subside.

  e

  Send a MSU and prescribe seven days of nitrofurantoin.
  Explanation: This woman has cystitis in pregnancy. Expert opinion is that urinary tract infections in pregnancy may increase the risk of fetal death, developmental delay and cerebral palsy. You must send an MSU for culture. A. A urine dipstick would not influence your decision whether or not to treat. B. Ibuprofen is contraindicated in pregnancy, because it encourages closure of the ductus arteriosus. C. It is correct to send an MSU, but empirical treatment should be start immediately and cannot wait for the results of the MSU. D. You must offer antibiotic treatment for cystitis in pregnancy. E. Nitrofurantoin has been used since the 1950s in pregnancy and has an excellent safety profile. You must send an MSU before starting antibiotics.
• 7
  You are a GP. A 28-year-old female presents to you with a five-day history of slight stinging on passing urine. She has a fever and right-sided loin pain, but is not tachycardic and her blood pressure is normal. She is not pregnant. What would you do next?
  Difficulty: Easy     Topic: Common infections
  a

  Ask for a urine dipstick.

  b

  Offer her ibuprofen for relief of symptoms.

  c

  Send an MSU and prescribe fourteen days of co-amoxiclav.

  d

  Advise her to drink a minimum of a litre of cranberry juice every day until symptoms subside.

  e

  Send an MSU and prescribe seven days of nitrofurantoin.
  Explanation: This woman has pyelonephritis (complicated UTI). She is unlikely to improve without antibiotic treatment. You must send an MSU for culture. If she was septic, you would also refer her to hospital. A. A urine dipstick would not influence your decision whether or not to treat. B. Ibuprofen is useful for symptom control but does not treat the underlying problem. C. The correct answer. Complicated UTIs should be treated with antibiotics for 10 to 14 days. The antibiotic choice should be changed in light of the MSU result. D. There is no evidence for the use of cranberry products in treating UTIs (Cochrane review 1998). They are not harmful, but are probably no more effective then drinking water. E. Nitrofurantoin is ineffective in pyelonephritis.
• 8
  In the management of urinary tract infections, a midstream urine should not be sent for:
  Difficulty: Easy     Topic: Common infections
  a

  Simple cystitis

  b

  Pyelonephritis

  c

  Cystitis in pregnancy

  d

  Recurrent cystitis

  e

  Cystitis following cystoscopy
  Explanation: A. The correct answer. Uncomplicated UTIs do not require an MSU to be sent. It is sufficient to do a urine dipstick. B. An MSU is mandatory in pyelonephritis (complicated UTI). C. An MSU s mandatory when treating cystitis in pregnancy. D. No MSU is required for a first episode, but is mandatory for recurrent UTIs. E. More unusual organisms can be introduced by instrumentation, so an MSU is mandatory.
• 9
  The bacterium that most common causes acute urinary tract infections is:
  Difficulty: Easy     Topic: Common infections
  a

  Pseudomonas aeruginosa

  b

  Escherichia coli

  c

  Klebsiella pneumoniae

  d

  Staphylococcus saprophyticus

  e

  Enterococcus faecalis
  Explanation: A. Pseudomonas aeruginosa is seldom a cause of UTIs unless there is instrumentation of the urinary tract such as cystoscopy or a urinary catheter. B. The correct answer. E .coli is a gut commensal and UTIs are believed to arise from contamination of the urinary tract from the gut. It accounts for 50 to 80% of all UTIs (Kahlmeter 2002, Farrell 2003). C. Klebsiella pneumoniae a less common cause of urinary tract infections (3 to 6%). Like E. coli, it is also a gut commensal. D. Staphylococcus saprophyticus as a cause of UTIs is associated with a new sexual partner ("honeymoon cystitis"). E. E. faecalis is a less common cause of a UTI (3 to 6% of all simple UTIs). It is a gut commensal.
• 10
  A 63-year-old man in a nursing home with severe dementia and has a long term indwelling catheter for prostatic obstruction. The district nurse noticed that the urine in his bag is cloudy, so she sent it to the laboratory for culture. You have been called out to see the patient, because the urine has now grown Klebsiella pneumoniae sensitive to co-amoxiclav. What should you do next?
  Difficulty: Medium     Topic: Common infections
  a

  Prescribe 14 days of co-amoxiclav.

  b

  Change the catheter.

  c

  Prescribe 7 days of co-amoxiclav.

  d

  Measure his temperature and ask the nurses looking after him whether he is more confused than normal.

  e

  Do nothing.
  Explanation: Urine samples from a longterm indwelling catheter are almost always culture-positive. This is often of no clinical significance, but if the patient is septic or unwell and there is no other obvious source, then he or she should be treated. A. You do not yet know if he is symptomatic. B. You do not know yet if he is symptomatic or how long this particular catheter has been in place. C. You do not yet know if he is symptomatic. D. The correct answer. E. Doing nothing is reasonable if the patient is asymptomatic, but you do not yet know whether this is the case.
• 11
  Varicella zoster virus (VZV) is responsible for a range of diseases and clinical syndromes. Which of the following does VZV not cause?
  Difficulty: Medium     Topic: Common infections
  a

  Herpes zoster

  b

  Herpes zoster ophthalmicus

  c

  Chicken pox

  d

  Herpes gladiatorum

  e

  Acute lymphocytic meningitis
  Explanation: A. Herpes zoster is a painful eruption that follows re-activation of VZV in the dorsal root ganglion of a sensory nerve. B. Herpes zoster involving the eye is called zoster ophthalmicus. C. Primary VZV infection causes chicken pox. D. Herpes gladiatorum or scrumpox is caused by herpes simplex virus and may involve the face, ears or neck. E. VZV is one of the causes of a viral meningitis, which is usually self-limiting and does not require specific treatment. There is some evidence aciclovir may shorten the duration of illness but is not mandatory.
• 12
  The blood markers of acute inflammation are:
  Difficulty: Easy     Topic: Common infections
  a

  Neutrophilia.

  b

  Lymphopaenia.

  c

  Eosinopaenia.

  d

  Elevated C-reactive protein (CRP).

  e

  All of the above.
  Explanation: In acute sepsis, the neutrophil count goes up (neutrophilia), the lymphocyte count goes down (lymphopaenia), the eosinophil count goes down (eosinopaenia) and the CRP goes up.
• 13
  Benzylpenicillin (penicillin G) will not provide cover for which of the following organisms?
  Difficulty: Easy     Topic: Common infections
  a

  Streptococcus pneumoniae (pneumococcus)

  b

  Penicillin-sensitive Staphylococcus aureus

  c

  Escherichia coli

  d

  Neisseria meningitidis

  e

  Streptococcus pyogenes (group A streptococcus)
  Explanation: Benzylpenicillin will cover Streptococcus pneumoniae, Staphylococcus aureus, Neisseria meningitidis and Streptococcus pyogenes, although varying levels of resistance occur worldwide. Escherichia coli is instrinsically resistant to penicillin.
• 14
  Compared to benzylpenicillin, amoxicillin provides additional cover for these bacteria:
  Difficulty: Hard     Topic: Common infections
  a

  Salmonella enterica, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pyogenes

  b

  Escherichia coli, Salmonella enterica, Klebsiella pneumoniae

  c

  Enterococcus faecalis, Escherichia coli, Salmonella enterica

  d

  Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus

  e

  Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae
  Explanation: Amoxicillin provides additional cover for Enterococcus faecalis, Escherichia coli and Salmonella enterica (but acquired resistance is now common). Benzylpenicillin already provides cover for Streptococcus pneumoniae and Streptococcus pyogenes, so amoxicillin offers no additional cover. Klebsiella pneumoniae is intrinsically resistant to both penicillin and amoxicillin (it has a chromosomal beta-lactamase). Staphylococcus aureus that is sensitive to penicillin will also be sensitive to amoxicillin; S. aureus that is resistant to penicillin will also be resistant to amoxicillin.
• 15
  Compared to amoxicillin, co-amoxiclav (Augmentin®) provides additional cover for these bacteria:
  Difficulty: Hard     Topic: Common infections
  a

  Bacillus fragilis, penicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae.

  b

  Methicillin-resistant Staphylococcus aureus (MRSA).

  c

  Penicillin-resistant Streptococcus pneumoniae (pneumococcus) and penicillin-resistant Staphylococcus aureus.

  d

  Escherichia coli and MRSA.

  e

  MRSA and penicillin-resistant pneumococcus.
  Explanation: Co-amoxiclav is combined formulation of amoxicillin and clavulanic acid (a beta-lactamase inhibitor). Some bacteria produce a beta-lactamase that breaks down amoxicillin and renders it ineffective. Co-amoxiclav therefore covers all the bacteria that amoxicillin covers, plus all bacteria whose mechanism of resistance is to produce a beta-lactamase that is inhibited by clavulanic acid. The mechanism of resistance in MRSA and in pencillin-resistant pneumococcus is by alteration of the penicillin-binding protein (so that amoxicillin cannot bind to its target), not by beta-lactamase production: this means that the addition of clavulanic acid has no effect. Penicillin-resistant Staphylococcus aureus, Kelbsiella pneumoniae and Bacillus fragilus produce a beta-lactamase that is inhibited by clavulanic acid, and are therefore susceptible to co-amoxiclav, but not to amoxicillin alone.
• 16
  Compared to co-amoxiclav (Augmentin®), piperacillin-taxobactam (Tazocin®) provides additional cover for these bacteria:
  Difficulty: Hard     Topic: Common infections
  a

  Burkholderia cepacia and penicillin-resistant Streptcoccus pneumoniae.

  b

  Penicillin-resistant Streptococcus pneumoniae (pneumococcus) and methicillin-resistant Staphylococcus aureus (MRSA)

  c

  Pseudomonas aeruginosa and Burkholderia cepacia

  d

  Pseudomonas aeruginosa and MRSA

  e

  MRSA
  Explanation: Piperacillin is an anti-pseudomonal penicillin that is active against Pseudomonas aeruginosa. Tazobactam is a broad spectrum beta-lactamase inhibitor. The spectra for c-amoxiclav and piperacillin-tazobactam are very similar, except that piperacillin-tazobactam will also cover Pseudomonas aeruginosa and Burkholderia pseudomallei. Neither co-amoxiclav nor piperacillin-tazobactam will cover MRSA.
• 17
  Compared to piperacillin-tazobactam (Tazocin®), meropenem provides additional cover for these bacteria:
  Difficulty: Medium     Topic: Common infections
  a

  Streptococcus pyogenes

  b

  Extended-spectrum beta-lactamase-producing Gram-negative bacteria (ESBL)

  c

  Pseudomonas aeruginosa.

  d

  Penicillin-resistant Streptococcus pneumoniae.

  e

  Methicillin-resistant Staphylococcus aureus (MRSA).
  Explanation: Both piperacillin-tazobactam and meropenem provide cover for Streptococcus pyogenes and Pseudomonas aeruginosa. Neither agent covers penicillin-resistant Streptococcus pneumoniae nor MRSA. The main advantage of meropenem over piperacillin-tazobactam is that meropenem is resistant to break down by ESBL-producing organisms: otherwise the spectra for both agents is very similar.
• 18
  Which of the following antibiotics does not provide empirical cover for methicillin-sensitive Staphylococcus aureus?
  Difficulty: Easy     Topic: Common infections
  a

  Co-amoxiclav

  b

  Vancomycin

  c

  Erythromycin

  d

  Flucloxacillin

  e

  Amoxicillin
  Explanation: The majority of methicillin-sensitive S. aureus isolates circulating in the UK are penicillin-resistant and the mechanism of resistance is the expression of a beta-lactamase. It is important to note that this was not always the case and until the 1950's the majority of S. aureus isolates were penicillin-sensitive. There are three possible ways of getting around this resistance: the first is to modify the penicillin so that it is not broken down by the beta-lactamase (e.g., flucloxacillin or cloxacillin). Alternatively, combine the antibiotic with a beta-lactamase inhibitor (e.g., co-amoxiclav). The third option is to use an antibiotic with a different mechanism of action completely (e.g., erythromycin targets the bacterial ribosome, unlike the penicillins, which target the bacterial cell wall). Vancomycin also targets the bacterial cell wall, but by a mechanism different from the penicillins and cephalosporins. Flucloxacillin (or another beta-lactamase-resistant penicillin) should always be preferred to alternatives such as erythromycin. Isolates of S. aureus that are penicillin-resistant will automatically be aminocillin-resistant as well.
• 19
  Which of the following antibiotics does not provide empirical cover for Pseudomonas aeruginosa?
  Difficulty: Easy     Topic: Common infections
  a

  Piperacillin-tazobactam (Tazocin®)

  b

  Meropenem

  c

  Co-amoxiclav (Augmentin®)

  d

  Gentamicin

  e

  Ciprofloxacin
  Explanation: Pseudomonas aeruginosa is intrinsically resistant to a large number of antibiotics. Of the penicillins, it is only sensitive to ticarcillin and piperacillin; of the cephalosporins, it is only sensitive to some third and fourth-generation cephalosporins such as ceftazidime and cefepime; of the carbapenems, it is sensitive to meropenem and imipenem, but not ertapenem; of the aminoglycosides, it is sensitive for gentamicin, amikacin and tobramycin, but not kanamycin or streptomycin; of the quonolones, it is sensitive to ciprofloxacin and levofloxacin, but not moxifloxacin. It is intrinsically resistant to all macrolides (erythromycin, clarithromycin, azithromycin).
• 20
  Which of the following antibiotics is not an aminoglycoside antibiotic?
  Difficulty: Easy     Topic: Common infections
  a

  Amikacin

  b

  Streptomycin

  c

  Tobramycin

  d

  Vancomycin

  e

  Gentamicin
  Explanation: The aminoglycosides are a group of antibiotics derived from soil bacteria. They are sugars modified by amino-groups. The aminoglycosides licensed for use in the UK are gentamicin, amikacin, tobramycin, neomycin and streptomycin. Outside the UK, kanamycin and paromomycin may also be available. As a class, they are broad spectrum antibiotics with action against both Gram-positive and Gram-negative bacteria and are believed to work by inhibiting the bacterial ribosome. They have no activity against anaerobes. Those derived from Streptomyces species end with -mycin but those from Micromonospora species end with -micin. Unfortunately, the name endings were previously used for other antibiotics also derived from soil bacteria (e.g., erythromycin, which was derived from Streptomyces erythraeus, now called Saccharopolyspora erythraea).
• 21
  Which of the following antibiotics is not a macrolide antibiotic?
  Difficulty: Easy     Topic: Common infections
  a

  Azithromycin

  b

  Clarithromycin

  c

  Erythromycin

  d

  Telithromycin

  e

  Vancomycin
  Explanation: The macrolides are a class of antibiotics that contain a macrolide ring. Erythromycin is a true antibiotic derived from Saccharopolyspora erythraea. Other drugs in the class (azithromycin, clarithromycin and telithromycin) may be synthesised from erythromycin. The macrolides work by inhibiting protein synthesis. Vancomycin is a glycopeptide antibiotic and acts on the bacterial cell wall.
• 22
  Which of the following is not a recognised adverse effect of quinolone antibiotics (e.g., ciprofloxacin, moxifloxacin)?
  Difficulty: Medium     Topic: Antibiotics
  a

  Convulsions

  b

  Clostridium difficile colitis

  c

  Photosensitivity

  d

  Shortening of the QT interval

  e

  Tendon rupture
  Explanation: A. Quinolones will lower the seizure threshold and should be used with caution in patients with epilepsy. B. C. difficile colitis is strongly associated with ciprofloxacin use. Quinolones should be avoided in the elderly, if possible. C. Photosensitive rashes are a rare side effect of quinolone use. D. The correct answer. Quinolones are associated with lengthening of the QT interval. E. Tendon rupture is a rare side effect of quinolone use, particularly when taken with carticosteroids.
• 23
  Which of the following is not a recognised adverse effect of doxycycline?
  Difficulty: Easy     Topic: Side effects
  a

  Discoloration of teeth in children.

  b

  Photosensitive rash.

  c

  Oesophagitis.

  d

  Glaucoma.

  e

  Benign intracranial hypertension.
  Explanation: A. Tetracyclines bind to calcium and are deposited in growing bones and teeth. They cause staining and may cause dental hypoplasia. They should therefore not be given to children under 12 years, or to pregnant or breast-feeding women. B. A photosensitive rash can occur. This can be a nuisance to travellers dependent on doxycycline as malaria prophylaxis. C. Oesophagitis (and less commonly, ulceration) is a common side effect of doxycycline. D. The correct answer. Although there exist rare reports of patients with doxycycline and glaucoma, no causal link has ever been shown. E. Benign intracranial hypertension is a rare side effect of tetracycline treatment that requires discontinuation.
• 24
  You are a junior doctor. A 19-year-old first-year university student has been admitted to hospital by her GP with a two-day history of fever and sore throat. On examination, the right jugulodigastric (JD) node is enlarged and tender, but the other cervical lymph nodes are not palpable. Both tonsils are enlarged, but the right tonsil is slightly more swollen more than the left, does not cross the midline and does not obstruct the airway. The back of the pharynx is erythematous. She is not able to swallow, and will require admission for intravenous fluids. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Bacterial tonsillitis

  b

  Gastroenteritis

  c

  Upper respiratory tract infection

  d

  Cervical spondylosis

  e

  Glandular fever
  Explanation: The asymmetrical tonsillitis and enlarged JD node are highly suggestive of a bacterial tonsillitis. A. The correct answer. B. The cardinal symptom of gastroenteritis is diarrhoea, which she does not have. C. A runny or blocked nose (coryza) or congested sinuses would be more typical of an upper respiratory tract infection. D. Cervical spondylosis is a degenerative disease of the cervical spine that normally causes neck pain and nerve root compression. E. Glandular fever would be expected to produce multiple shotty cervical lymph nodes (not a solitary JD node) and symmetrical (not asymmetrical) tonsillar enlargement, possibly with palpable splenomegaly.
• 25
  You are a junior doctor. A 19-year-old first-year university student has been admitted to hospital by her GP with a two-day history of fever and sore throat. On examination, the right jugulodigastric (JD) node is enlarged and tender, but the other cervical lymph nodes are not palpable. Both tonsils are enlarged, but the right tonsil is slightly more swollen more than the left, does not cross the midline and does not obstruct the airway. The back of the pharynx is erythematous. She is not able to swallow, and will require intravenous fluids. What antibiotic treatment should you start?
  Difficulty: Medium     Topic: -
  a

  Moxifloxacin

  b

  Benzylpenicillin

  c

  Clarithromycin

  d

  Metronidazole

  e

  Ibuprofen
  Explanation: The asymmetrical tonsillitis and enlarged JD node are highly suggestive of a bacterial tonsillitis. The most common cause of bacterial tonsillitis is Streptococcus pyogenes (group A streptococcus). Penicillin (oral penicillin V or intravenous benzylpenicillin) is the treatment of choice for S. pyogenes and all other treatment options are inferior. Anaerobes such as Fusobacterium species sometimes cause tonsillitis, but these are usually also susceptible to penicillin, so no additional antibiotic cover is required. For patients who are able to swallow, syrup preparations are kinder than tablets for patients with a sore throat, and are just as effective. A. Moxifloxacin may cover S. pyogenes, but this is unpredictable and susceptibility testing is required. B. The correct answer. C. Clarithromycin may cover S. pyogenes, but this is unpredictable and susceptibility testing is required. D. Metronidazole does not cover S. pyogenes and is not appropriate. E. Ibuprofen is not an antibiotic. Bacterial tonsillitis is self-limiting and the majority of cases will eventually resolve without treatment, however, she is unwell enough to require hospital admission and an antibiotic is warranted to try to reduce the duration of illness.
• 26
  You are the junior doctor on-call at a busy medical admissions unit. A 19-year-old first-year university student comes to see you with a two-day history of fever and sore throat. On examination, she has bilaterally enlarged tonsils. Her neutrophil count is 3.2, her lymphocyte count is 7.3 and her monocyte count is 4.8. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Bacterial tonsillitis

  b

  Gastroenteritis

  c

  Upper respiratory tract infection

  d

  Cervical spondylosis

  e

  Glandular fever
  Explanation: Fever, sore throat and bilateral tonsillitis are all symptoms of glandular fever (acute EBV infection). Missing from the clinical picture are lymphadenopathy and splenomegaly (but these are not invariably present). The normal neutrophil count argues against a bacterial infection. The lymphocyte count is high. The elevated monocyte count in glandular fever is an artefact: these are actually atypical lymphocytes (large mononuclear cells with abundant cytoplasm) that the automated system has miscounted as monocytes (hence the alternative name for glandular fever, which is "infectious mononucleosis", because the blood film is full of mononuclear cells). A. The neutrophil count is normally enlarged in bacterial infection, making bacterial tonsillitis much less likely. B. The cardinal symptom of gastroenteritis is diarrhoea. C. An upper respiratory tract infection would be expected to present with a blocked or runny nose (coryza) or sinus congestion in addition to the fever and sore throat. D. Cervical spondylosis is a degenerative disease of the cervical spine presenting with neck pain and sometime nerve root compression. E. The correct answer.
• 27
  You are the junior doctor on-call at a busy medical admissions unit. A 19-year-old first-year university student comes to see you with a two-day history of fever and sore throat. On examination, she has bilaterally enlarged tonsils. Her neutrophil count is 3.2, her lymphocyte count is 7.3 and her monocyte count is 4.8. What antibiotic treatment is required?
  Difficulty: Medium     Topic: -
  a

  Moxifloxacin

  b

  Erythromycin

  c

  Co-amoxiclav (Augmentin®)

  d

  Amoxicillin

  e

  Nothing
  Explanation: The combination of fever, acute symmetrical tonsillar enlargement and mononuclear cells (high lymphocyte count and artefactually high monocyte count) on the blood count is highly suggestive of viral, not bacterial, infection. The most likely diagnosis is acute Epstein-Barr virus (EBV) infection (glandular fever), but the differential diagnosis includes HIV seroconversion illness and acute cytomegalovirus (CMV) infection. None of the differentials respond to antibiotic treatment. A–C. Antibiotics are not effective against viral infections. D. Giving amoxicillin to a patient with glandular fever will result in a widespread maculopapular rash and this does not mean the patient is allergic to penicillin. E. The correct answer.
• 28
  You are the junior doctor on-call at a busy medical admissions unit. A 19-year-old first-year university student comes to see you with a two-day history of fever and sore throat. On examination, she has bilaterally enlarged tonsils. Her neutrophil count is 3.2, her lymphocyte count is 2.5 and her monocyte count is 5.0. Her monospot test is negative. EBV NA (nuclear antigen) IgG is positive. What test must you do next?
  Difficulty: Medium     Topic: Common infections
  a

  HIV test

  b

  EBV serology

  c

  CMV serology

  d

  Influenza serology

  e

  Nothing
  Explanation: A. The clinical picture is that of glandular fever, but the monospot test (a screening test for glandular fever) is negative. A positive EBV NA IgG confirms previous EBV infection (some time in the distant past), which means the current illness cannot be due to acute EBV infection (i.e., glandular fever). Acute HIV seroconversion illness can look identical to glandular fever and should always be considered in the differential diagnosis, because it is treatable and the consequences of missing the diagnosis are disastrous. B. EBV serology has already been done and she does not have acute EBV infection (we have the EBV NA IgG result). C. CMV can cause an illnes similar to glandular fever, but it is self-limiting with no specific treatment and doing CMV serology is therefore of academic interest only, since specific treatment is not required. D. Influenza tends to cause a cough, coryza, cephalgia and myalgia. The clinical picture is not that of influenza and influenza in a young person does not normally require specific treatment anyway, so making the diagnosis would not change management. E. You must do an HIV test.
• 29
  You are the junior doctor on-call at a busy medical admissions unit. A 19-year-old first-year university student comes to see you with a five-day history of fever and sore throat. Her GP started a course of oral penicillin V (phenoxymethylpenicillin) three days ago but she has continued to get worse and now cannot swallow solids or liquids. On examination, she is speaking with a muffled (‘hot potato’) voice. Her right jugolodigastric node is enlarged and tender. She is barely able to open her mouth (trismus), but with a tongue depressor, you can just see that the right tonsil is markedly enlarged and is pushing the uvula to the left. Her airway is patent.What is the diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Uncomplicated bacterial tonsillitis

  b

  Peritonsillar abscess (quinsy)

  c

  Viral tonsillitis

  d

  Upper respiratory tract infection

  e

  Glandular fever
  Explanation: The patient has a 'hot potato' voice, trismus, and an acutely enlarged tonsil that is crossing the midline. These are all features of a peritonsillar abscess (commonly called a 'quinsy'). The definitive treatment is referral to an ENT surgeon for drainage. Intravenously benzylpenicillin should be prescribed if the patient is unable to swallow (which is the most likely scenario) or oral penicillin V if they are able to take medicines by mouth. A. The patient has tonsillitis complicated by an abscess. B. The correct answer. C. Viral tonsillitis does not cause abscesses. D. An upper respiratory tract infection most frequently presents with a runny or blocked nose (coryza) and congested sinuses. E. Glandular fever is a viral illness that can present with tonsillitis but does not cause abscesses.
• 30
  You are the junior doctor on-call at a busy medical admissions unit. A 19-year-old first-year university student comes to see you with a five-day history of fever and sore throat. Her GP started a course of oral amoxicillin two days ago. She has now come to A&E with a rash. On examination, she has a widespread, intensely pruritic, maculopapular rash. There is bilateral symmetrical tonsillar enlargement and multiple small mobile lymph nodes in her neck. Her full blood count shows 2.5 neutrophils and 9.6 lymphocytes. What should you do next.?
  Difficulty: Medium     Topic: Common infections
  a

  Escalate from amoxicillin to co-amoxiclav (Augmentin®).

  b

  Stop amoxicillin and re-assure.

  c

  Re-assure and persist with amoxicillin.

  d

  Give a dose of ceftriaxone immediately.

  e

  Perform a blood film.
  Explanation: She has glandular fever. Giving amoxicillin to a patient with glandular fever will result in a maculopapular rash. This is not a true allergic reaction to penicillin in that the rash will not recur if the patient is rechallenged with amoxicillin at a later date. The same reaction may occur with ampicillin or cephalosporins. A. She does not have a bacterial infection and the antbiotics should be stopped. B. The correct answer. Her rash is due to the amoxicillin. The treatment for glandular fever is supportive only. C. She does not have a bacterial infection and the amoxicillin should be stopped. D. The rash of meningococcal bacteriaemia is usually flat and purpuric. It is not maculopapular. E. A blood film in glandular fever will show atypical lymphocytes, but since the diagnosis is already clear, doing a blood film adds nothing to the management of this patient.
• 31
  You are a junior doctor on-call on a medical admissions unit in Scotland in January. A frail 89-year-old woman from a nursing home is referred into hospital for intravenous rehydration. She has vomited eight times overnight and had one bout of watery diarrhoea. In the past five days, five other residents of the nursing home have also been unwell with diarrhoea and vomiting, with roughly one new case each day. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Norwalk virus gastroenteritis

  b

  Staphylococcal food poisoning

  c

  Rotavirus gastroenteritis

  d

  Salmonella gastroenteritis

  e

  Campylobacter gastroenteritis
  Explanation: Norwalk virus (the only species within the genus, norovirus) is a common cause of viral gastroenteritis. It tends to circulate in the winter and is highly contagious. It commonly causes outbreaks in closed communities (e.g., hospital wards, nursing homes, or cruise ships). The virus is commonly known in the media as 'winter vomiting virus'. A. The correct diagnosis. B. Staphylococcal food poisoning usually causes a point source outbreak, with patients who ate the contaminated food becoming unwell at roughly the same time (within a few hours of each other). C. Rotavirus is a common cause of outbreaks in infants and young children. Rotavirus does affect adults, but severe outbreaks such as this are rarely due to rotavirus. D. Diarrhoea is more prominent in Salmonella gastroenteritis, not vomiting. E. Diarrhoea is more prominent in Campylobacter gastroenteritis, not vomiting.
• 32
  You are a GP. There are six vomiting patients in your waiting room. They were all guests at the same wedding the previous day and started vomiting during the night or the early hours of the morning. They do not recall meeting any unwell guests at the wedding. At the reception, all the unwell guests remember eating the custard. What is the most likely diagosis?
  Difficulty: Easy     Topic: Common infections
  a

  Norwalk virus gastroenteritis

  b

  Staphylococcal food poisoning

  c

  Rotavirus gastroenteritis

  d

  Salmonella gastroenteritis

  e

  Campylobacter gastroenteritis
  Explanation: The near-simultaneous onset suggests a point-source outbreak rather than transmission from person to person. The common source is probably the custard, which means an incubation period of only a few hours. The most likely diagnosis is therefore food poisoning rather than gastroenteritis. Only rehydration and conservative treatment are required. A. Norwalk virus is a highly infectious agent commonly transmitted from person to person in the winter. Transmission from a a single carrier at the wedding is possible, but less likely since an infectious contact is likely to have been symptomatic and unwell and at least one of the guests should have remembered such a contact. B. The correct answer. S. aureus may contaminate cooked meat or egg products (such as custard). The organism produces a large number of enterotoxins that are capable of causing food poisoning. Disease is caused by ingestion of the pre-formed toxin and not S. aureus infection. The usual source is the nose or fingers of a food handler contaminating food that is already cooked. C. Rotavirus outbreaks are rare in otherwise healthy adults. D, E. The incubation period is too short for Salmonella or Campylobacter gastroenteritis.
• 33
  You are a GP. A 10-year-old boy attends your clinic with a three-day history of fever, watery diarrhoea and abdominal cramps. He is normally fit and well and has had all his usual childhood vaccinations. He received a pet baby turtle for his birthday a week ago. What is the diagnosis?
  Difficulty: Medium     Topic: Common infections
  a

  Norwalk virus gastroenteritis

  b

  Staphylococcal food poisoning

  c

  Rotavirus gastroenteritis

  d

  Salmonella gastroenteritis

  e

  Campylobacter gastroenteritis
  Explanation: Young reptiles (turtles, tortoises, snakes) and birds (chicks and ducklings) may be asymptomatic carriers of Salmonella and have frequently been identified as the source of outbreaks when kept as pets. The history of recent contact with a pet reptile suggests the diagnosis of Salmonella gastroenteritis. A, B. The duration of illness is too long for Norwalk virus or for food poisoning. Also, in both of these illnesses, vomiting is more prominent than diarrhoea. C. The child is a little too old to have rotavirus. Most symptomatic infections occur in children under the age of five. D. The correct answer. E. The symptoms would be compatible with Campylobacter, but the history of contact with a pet reptile suggests Salmonella.
• 34
  You are GP. A 24-year-old white Caucasian woman attends your clinic with a one-week history of bloody diarrhoea twice to three-times a day. This is the third episode of diarrhoea she has had in the last six months. Each prior episode settled with supportive treatment only and did not require hospital admission. She is pale and tells you she has lost weight. She has no pets and has never travelled outside of Western Europe. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Common infections
  a

  Staphylococcal food poisoning

  b

  Norwalk virus gastroenteritis

  c

  Inflammatory bowel disease

  d

  Colorectal adenocarcinoma

  e

  Salmonella gastroenteritis
  Explanation: The recurrent nature of her illness suggests that an infection is unlikely. The history of most suggestive of inflammatory bowel disease. A. The duration of illness is too long for food poisoning which normally resolves within 72 hours. B. The duration of illness is too long for Norwalk virus, which normally resolves within 72 hours. C. The correct answer. D. It is unusual for bowel cancer to cause frank bleeding, although occult bleeding is common. Also, her young age makes bowel cancer less likely. E. The relapsing and remitting course of her illness argues against an infectious cause.
• 35
  Which of the following bacteria is not commonly (≥5%) implicated in exacerbations of chronic obstructive pulmonary disease (COPD)?
  Difficulty: Easy     Topic: Common infections
  a

  Streptococcus pneumoniae

  b

  Candida albicans

  c

  Haemophilus influenzae

  d

  Haemophilus parainfluenzae

  e

  Moraxella catarrhalis
  Explanation: The most commonly isolated bacteria are Haemophilus influenzae (11%), Streptococcus pneumoniae (10%), Moraxella catarrhalis (10%) and Haemophilus parainfluenzae (10%). Pseudomonas aeruginosa is responsible for only 4% of exacerbations. Important non-bacterial causes include respiratory viruses (such as influenza) and environmental pollution. Candida albicans is a fungus and is not a bacterium. It is not an important cause of COPD exacerbations.
• 36
  Which of the following bacteria is not commonly (≥5%) implicated in exacerbations of chronic obstructive pulmonary disease (COPD)?
  Difficulty: Medium     Topic: Common infections
  a

  Haemophilus influenzae

  b

  Haemophilus parainfluenzae

  c

  Pseudomonas aeruginosa

  d

  Moraxella catarrhalis

  e

  Streptococcus pneumoniae
  Explanation: The most commonly isolated bacteria are H. influenzae (11%), S. pneumoniae (10%), M. catarrhalis (10%) and H. parainfluenzae (10%). P. aeruginosa is responsible for only 4% of exacerbations, and most guidelines therefore do not recommend treating for Pseudomonas empirically. Important non-bacterial causes include respiratory viruses (such as influenza) and environmental pollution.
• 37
  You are a junior doctor on-call at a district general hospital. A 64-year-old man with known chronic obstructive pulmonary disease is admitted with a two-day history of increasing shortness of breath and purulent sputum. His respiratory rate is 20 and oxygen saturations are 90% on air, but have increased to 92% with nebulised salbutamol started by A&E. What antibiotic treatment should you start?
  Difficulty: Easy     Topic: Common infections
  a

  Piperacillin-tazobactam (Tazocin®)

  b

  Ciprofloxacin

  c

  Doxycycline

  d

  Flucloxacillin

  e

  Benzylpenicillin
  Explanation: BTS/NICE guidelines for COPD advise an aminopenicillin (i.e., amoxicillin or ampicillin), a macrolide, or tetracycline to treat acute exacerbations of COPD. The most commonly isolated bacteria are Haemophilus influenzae (11%), Streptococcus pneumoniae (10%), Moraxella catarrhalis (10%) and Haemophilus parainfluenzae (10%) (Sapey Thorax 2006). Pseudomonas aeruginosa is responsible for only 4% of exacerbations: it is therefore not necessary to cover Pseudomonas empirically, but it should be considered if the patient fails to respond. Important non-bacterial causes include respiratory viruses and environmental pollution. A. Piperacillin-tazobactam is unnecessarily broad spectrum. B. Ciprofloxacin has no useful activity against Streptococcus pneumoniae. C. The correct answer. D. Flucloxacillin does not cover Haemophilus or Streptococcus pneumoniae. E. Penicillin has no useful activity against Haemophilus.
• 38
  You are a junior doctor on-call at a district general hospital. You are called to the ward to see a 64-year-old man who has just had a seizure. He was admitted two days ago with an infective exacerbation known chronic obstructive pulmonary disease and is currently on controlled oxygen therapy, salbutamol nebulisers, clarithromycin, prednisolone and theophylline. By the time you arrive, he has recovered fully from the seizure and is clinically stable. This is his first fit and he is not known to have epilepsy. What should you do now to prevent further seizures?
  Difficulty: Hard     Topic: Common infections
  a

  Change the clarithromycin to moxifloxacin.

  b

  Stop the prednisolone to hydrocortisone.

  c

  Perform urgent computed tomography (CT scan) of the head.

  d

  Stop the theophylline.

  e

  Start intravenous phenytoin.
  Explanation: This patient's seizure is due to theophylline toxicity. Macrolides (such as clarithromycin) and quinolones (such as moxifloxacin) will cause accumulation of theophylline. This may result in convulsions or cardiac arrhythmias. BTS/NICE guidelines for COPD therefore advise reducing the dose of theophylline in patients on macrolides or fluoroquinolones. A. Moxifloxacin has the same interaction with theophylline that clarithromycin has. What is worse, moxifloxacin will also lower the seizure threshold. B. The prednisolone is not responsible for the seizure. C. This seizure is due to theophylline toxicity and not an intracranial lesion. Imaging is unlikely to be helpful. D. The correct answer. E. The patient is now stable. Since theophylline is the likely cause, stopping the theophylline is more important than trying to treat the seizures with phenytoin.
• 39
  You are a GP. An 64-year-old man attends your clinic, having just been discharged from hospital. He was admitted for an infective exacerbation of COPD and his sputum grew Moraxella catarrhalis. This is his seventh admission to hospital in the last twelve months. He asks you for long term antibiotic prophylaxis. What antibiotic do you recommend?
  Difficulty: Easy     Topic: Common infections
  a

  Explain that prophylaxis is not recommended.

  b

  Start low dose penicillin V.

  c

  Start low dose ciprofloxacin.

  d

  Start low dose clarithromycin.

  e

  Start low dose co-amoxiclav (Augmentin®).
  Explanation: BTS/NICE guidelines for COPD specifically state that prophylactic antibiotics are not recommended. There is no evidence that long term antibiotics prevent exacerbations. On the contrary, there is an increased risk of colonisation by drug-resistant organisms, so that when exacerbations do occur, they are harder to treat. A. The correct answer. B. Antibiotic prophylaxis is not recommended. In any case, Moraxella catarrhalis is intrinsically resistant to penicillin. C–E. Antibiotic prophylaxis is not recommended.
• 40
  Which of the following antibiotics does not provide empirical cover for anaerobic infection?
  Difficulty: Hard     Topic: Common infections
  a

  Metronidazole

  b

  Meropenem

  c

  Piperacillin-tazobactam

  d

  Ciprofloxacin

  e

  Clindamycin
  Explanation: Metronidazole is commonly used to cover anaerobic infection empirically, however, there are a number of antibiotics that provide good cover for anaerobic bacteria and therefore no additional cover with metronidazole is required (Brook Clin Microbiol Rev 2013). Of the penicillins, preparations that include a beta-lactamase inhibitor (e.g., co-amoxiclav, ampicillin-sulbactam, piperacillin-tazobactam) all have good activity against anaerobes. Of the fluoroquinolones, this includes moxifloxacin and gatifloxacin (but not ciprofloxacin or levofloxacin). Carbapenems such as meropenem and ertapenem provide excellent cover for anaerobes. Until the 1990's, clindamycin was used routinely to cover anaerobes empirically in the US. Of the cephalosporins, only cefoxitin is active. Chloramphenicol and tigecycline both provide excellent anaerobic cover.
• 41
  You are a junior doctor on-call at a district general hospital. A 67-year-old woman presents to you with a two-day history of fever and cough productive of green sputum. On examination, she is confused, her temperature is 38.6°C, respiratory rate 28 breaths per minute, blood pressure 95/70, and she has crackles at the base of her right lung. Her blood results are as follows: sodium 142 mmol/l, potassium 4.5 mmol/l, urea 8.2 mmol/l, creatinine 109 µmol/l, C-reactive protein 84, haemoglobin 112 g/l, and total white cells 11.2. She has consolidation in the right lower lobe on her chest radiograph. What is her CURB-65 score?
  Difficulty: Easy     Topic: Common infections
  a

  1

  b

  2

  c

  3

  d

  4

  e

  5
  Explanation: The CURB65 score (Lim Thorax 2003) is a simple severity scoring system recommended by the British Thoracic Society for the assessment of severity of community acquired pneumonia. Award one point for each of the following: 1. new Confusion, 2. Urea >7 mmol/l, 3. Respiratory rate ≥30, 4. Blood pressure systolic <90 or diastolic ≤60, 5. age ≥ 65. Patients with a CURB65 score of 0 or 1 are at low risk of death and can be managed in the community. A score of 2 indicates moderate risk and short inpatient stay or close outpatient monitoring should be considered. A score of 3 or more is high risk and hospital admission is recommended. this patient scores 3 for confusion, urea and age.
• 42
  You are a GP. A 65-year-old woman presents to you with a two-day history of fever and cough productive of green sputum. On examination, she is alert and orientated, her temperature is 38.6°C, respiratory rate 28 breaths per minute, blood pressure 134/84, and she has crackles at the base of her right lung. What is her CRB-65 score?
  Difficulty: Easy     Topic: Common infections
  a

  0

  b

  1

  c

  2

  d

  3

  e

  4
  Explanation: The CRB65 score is a modified version of the CURB65 score that omits urea and is the severity scoring system recommended by the British Thoracic Society for use in the community, where blood results are not immediately available. Award one point for each of the following: 1. new Confusion, 2. Respiratory rate ≥30, 3. Blood pressure systolic <90 or diastolic ≤60, 4. age ≥ 65. A score of 0 indicates low risk and hospitalisation is not normally recommended. A score of 1 or 2 indicates increased risk and the BTS you should consider referral to hospital for further assessment. A score of 3 or 4 indicates high risk of death and urgent referral to hospital is indicated. This patient scores 1 for her age only.
• 43
  You are a GP in the UK. A 64-year-old woman presents to you with a two-day history of fever and cough productive of green sputum. She is normally fit and well with no allergies. She has not history of foreign travel. On examination, she is alert and orientated, her temperature is 38.6°C, respiratory rate 28 breaths per minute, blood pressure 134/84, and she has crackles at the base of her right lung. What antibiotic should you prescribe her?
  Difficulty: Easy     Topic: Common infections
  a

  Clarithromycin

  b

  Amoxicillin

  c

  Doxycycline

  d

  Co-amoxiclav (Augmentin®)

  e

  Moxifloxacin
  Explanation: This woman's CRB65 score is 0 and it would therefore be best to manage her in the community. The British Thoracic Society guidelines for community acquired pneumonia (2009) treated in the community is oral amoxicillin. This is based on the fact that penicillin-resistance in Streptococcus pneumoniae in the UK is under 5%. A. This would be an appropriate alternative if the patient were penicillin allergic. B. The correct answer for the UK. C. This would be an appropriate alternative if the patient were penicillin allergic. D. Co-amoxiclav is inappropriate because it is very broad spectrum and provides additional cover for Gram-negative organisms that do not normally cause community-acquired pneumonia. Co-amoxiclav does not cover penicillin-resistant pneumococcus. E. Moxifloxacin is appropriate in countries where rates of resistance to penicillin in Streptococcus pneumoniae is high.
• 44
  Which of the following is not a condition for starting empirical oseltamivir (Tamiflu®) treatment for influenza.
  Difficulty: Easy     Topic: Common infections
  a

  Clinical features of influenza

  b

  Onset of symptoms <48h in adults (<36h in children)

  c

  Age 65 and over

  d

  Diabetes mellitus

  e

  Diarrhoea
  Explanation: The UK NICE guidelines for the empirical use oseltamivir, zanamivir and amantidine for the treatment of influenza state that all of the following three conditions must be met before empirical oseltamivir can be given: (1) National surveillance shows that influenza A or B is circulating, (2) the patient is in an 'at-risk' group, and (3) the patients has presented within 48h of onset of an influenza-like illness (36h for children). The at-risk groups are patients with chronic respiratory disease, chronic heart disease, chronic renal disease, chronic liver disease, chronic neurological conditions, diabetes mellitus, age ≥65 and immunosuppression. The guidelines do not cover pandemic influenza. The guidance is due for review in Nov 2013. A-D. These are all conditions for starting oseltamivir, although only A and B are compulsory. E. Diarrhoea can be a feature of any systemic infection, but it is not usual in influenza.
• 45
  You are a junior doctor in a busy medical admissions unit. A 53-year-old man presents with a one-day history of fever and rapidly progressive pain, redness and swelling of the right leg following an insect bite. He is normally fit and well, with no allergies. On examination, he is apyrexial, with a normal pulse and blood pressure. There is an erythematous, indurated area of cellulitis on his right leg, starting at his foot and progressing upwards to a clearly demarcated line just below the knee. An ultrasound performed immediately after admission excludes a deep vein thrombosis. What antibiotic should you start?
  Difficulty: Medium     Topic: Common infections
  a

  Intravenous flucloxacillin

  b

  Oral flucloxacillin

  c

  Oral clarithromycin

  d

  Oral penicillin V (phenoxymethylpenicillin)

  e

  Oral doxycycline
  Explanation: This patient has cellulitis with no systemic features (e.g., fever, tachycardia, hypotension, or acute confusion) and no co-morbidities. The NICE Clinical Knowledge Summary for cellulitis (Sep 2012) therefore recommends oral antibiotics and hospital admission is unnecessary. A. The patient does not require hospital admission and intravenous antibiotics are difficult to give in the community. B. The correct answer. At high doses, it will cover the two most common causes of cellulitis, which are Streptococcus pyogenes and Staphylococcus aureus. C. Erythromycin is an acceptable second-line treatment for cellulitis if flucloxacillin cannot be used, but resistance to erythromycin is more common than to flucloxacillin. Erythromycin is also commonly associated with diarrhoea (it promotes gut motility). It should therefore not be used as first line treatment. D. Penicillin V will cover Streptococcus pyogenes, but resistance is common in Staphylococcus aureus. It should therefore only be used if infection can be proved to be due to Streptococcus pyogenes. E. Doxycycline is an acceptable second-line treatment if flucloxacillin cannot be given. Doxycycline is less well tolerated and can cause photosenstive rash, oesophagitis. Nausea is also more common with doxycycline than with flucloxacillin.
• 46
  You are a junior doctor in a busy medical admissions unit. A 53-year-old man presents with a one-day history of fever and rapidly progressive pain, redness and swelling of the right leg following a small cut on his leg. He is normally fit and well, with no allergies. On examination, he is apyrexial, with a normal pulse and blood pressure. There is an erythematous, indurated area of cellulitis on his right leg, starting at his foot and progressing upwards to a clearly demarcated line just below the knee. An ultrasound performed immediately after admission excludes a deep vein thrombosis. What oral antibiotic should you start?
  Difficulty: Easy     Topic: Common infections
  a

  Ciprofloxacin

  b

  Flucloxacillin

  c

  Clarithromycin

  d

  Penicillin V (phenoxymethylpenicillin)

  e

  Doxycycline
  Explanation: This patient has cellulitis with no systemic features (e.g., fever, tachycardia, hypotension, or acute confusion) and no co-morbidities. The NICE Clinical Knowledge Summary for cellulitis (Sep 2012) therefore recommends oral antibiotics and hospital admission is unnecessary. The most common cause is Streptococcus species (groups A, C and G in decending order of frequency), with Staphylococcus aureus a close second. A. Ciprofloxacin cover for Gram-positive organisms is extremely unreliable (>20% of S. aureus isolates in the UK are resistant). It should not be used to treat suspected Gram-negative infection. B. The correct answer. At high doses, flucloxacillin will cover the two most common causes of cellulitis, which are Streptococcus species and Staphylococcus aureus. Flucloxacillin is not available in the US and dicloxacillin is a good alternative. C. Erythromycin is an acceptable second-line treatment for cellulitis if flucloxacillin cannot be used, but resistance in Streptococcus to erythromycin is more common than to high dose flucloxacillin. Erythromycin is also commonly associated with adverse effects such as diarrhoea (it promotes gut motility). It should therefore not be used as first line treatment. D. Penicillin V will cover most Streptococcus species, but resistance is common in Staphylococcus aureus. It should therefore only be used if infection can be proved to be due to Streptococcus and not Staphylococcus aureus. E. Doxycycline is an acceptable second-line treatment if flucloxacillin cannot be given. Doxycycline is less well tolerated and can cause photosensitive rash and oesophagitis. Also, ~6% of Streptococcus pyogenes isolates are resistant to doxycycline. Nausea is also more common with doxycycline than with flucloxacillin. Doxycycline should therefore only be used if flucloxacillin cannot be used.
• 47
  You are a junior doctor in an accident and emergency department in the UK. A 53-year-old man presents immediately following a bite from his neighbour’s dog. He is normally fit and well, with no allergies. On examination, he is apyrexial, with a normal pulse and blood pressure. You can see deep teeth marks where the animal has bitten him, but have now stopped bleeding. What do you do next?
  Difficulty: Medium     Topic: Common infections
  a

  Re-assure and advise to return if signs of infection appear.

  b

  Check tetanus vaccination status and offer a booster if indicated.

  c

  Offer flucloxacillin antibiotic prophylaxis.

  d

  Check tetanus vaccination status and offer a booster if indicated. Offer flucloxacillin antibiotic prophylaxis.

  e

  Check tetanus vaccination status and offer a booster if indicated. Offer co-amoxiclav antibiotic prophylaxis.
  Explanation: The skin has been breached and potentially inoculated with two groups of potential pathogens: 1. skin organisms such as Staphylococcus aureus, and 2. oral commensals in the dog. Prophylactic antibiotic therapy must therefore cover oral anaerobes (e.g., Fusobacterium species, Peptostreptococcus species and Prevotella species) and the Gram-negative coccobacillus, Pasturella multocida (an important oral commensal of both cats and dogs that can cause bacteraemia, osteomyelitis, endocarditis and meningitis in humans). Tetanus vaccination should always be offered if not up-to-date.The UK has been rabies-free since 1922. A. This man is at risk of infection and should be offered antibiotic prophylaxis. B. It is correct to check tetanus vaccination status, but antibiotic prophylaxis should also be offered. C. Neither erythromycin nor clindamycin covers Pasturella multocida. Clindamycin offers good cover for both Gram-positives and anaerobes. D. Flucloxacillin does not cover Pasteurella multocida. E. The correct answer. Co-amoxiclav covers Streptococcus species, most Staphylococcus, Pasteurella multocida and anaerobes.
• 48
  You are a junior doctor in an accident and emergency department in the UK. A 53-year-old man presents immediately following a bite from his pet cat. He is normally fit and well, but is allergic to penicillin (anaphylactic reaction). On examination, he is systemically well, however, you can see teeth marks where the cat has bitten him, with an area of surrounding erythema and induration. His tetanus immunisation is up-to-date. What do you do next?
  Difficulty: Hard     Topic: Common infections
  a

  Re-assure and discharge.

  b

  Prescribe oral erythromycin and metronidazole.

  c

  Prescribe oral clindamycin.

  d

  Prescribe oral doxycycline and metronidazole.

  e

  Prescribe oral co-amoxiclav (Augmentin®)
  Explanation: This man has cellulitis following a cat bite. The causes of any cellulitis following a breach in the skin include Streptoccocus species as well as Staphylococcus aureus. However, the differential here is much wider and also includes possible pathogens the oral commensals of a cat. Empirical antibiotic therapy must therefore cover also oral anaerobes (e.g., Fusobacterium species, Peptostreptococcus species and Prevotella species) and the Gram-negative coccobacillus, Pasturella multocida (an important oral commensal of both cats and dogs that can cause bacteraemia, osteomyelitis, endocarditis and meningitis in humans). The UK has been rabies-free since 1922. A. This man has active infection that should be treated. B, C. Neither erythromycin nor clindamycin covers Pasturella multocida. Clindamycin offers good cover for both Gram-positives and anaerobes. D. The correct answer. Doxycycline covers Streptococcus, Staphylococcus and Pasturella multocida. Doxycycline does not reliably cover anaerobes, so metronidazole must be added. E. This would ordinarily be an excellent choice, but the patient is allergic to penicillin.
• 49
  You are a junior doctor in an accident and emergency department in the UK. A 53-year-old man presents with a swollen right hand five days after a pub brawl. On examination, he is systemically well, however, you can see teeth marks over his knuckles, with surrounding erythema and induration. His tetanus immunisation is up-to-date. What antibiotics should you prescribe?
  Difficulty: Medium     Topic: Common infections
  a

  Flucloxacillin

  b

  Benzylpenicillin

  c

  Co-amoxiclav (Augmentin®)

  d

  Ciprofloxacin

  e

  Clindamycin
  Explanation: This man has a so-called "reverse" human bite (he was not bitten, but punched another man in the mouth). The antibiotic choice should cover Gram-positives (principally, Streptococcus species and Staphylococcus aureus), which are the usual causes of cellulitis. However, they also need to cover potentially pathogenic commensals of the human mouth, which include Eikenella corrodens and anaerobes (Fusobacterium species, Prevotella species and Peptostreptococcus species). He should also be referred to a hand surgeon to consider infection of the deep spaces of the hand that may require drainage. A. Flucloxacillin does not provide good cover for anaerobes. B. Benzylpenicillin will not cover Staphylococcus aureus, but provides reasonable cover for oral anaerobes. C. The correct answer. D. Ciprofloxacin will not cover provide reliable cover for Gram-positives (Streptococcus and Staphylococcus species). It also provides poor cover for anaerobes. It will, however, cover Eikenella corrodens. E. Clindamycin will cover Streptococcus species, Staphylococcus aureus and anaerobes, but Eikenella corrodens is innately resistant to all macrolides as well as clindamycin.
• 50
  You are a junior doctor in an accident and emergency department in the UK. A 53-year-old man presents with a swollen right leg five days after he cut himself swimming in a freshwater lake. On examination, he is systemically well, however, you can see that there is an infected laceration on his leg with surrounding erythema and induration. His tetanus immunisation is up-to-date. What oral antibiotics should you prescribe?
  Difficulty: Hard     Topic: Common infections
  a

  Amoxicillin and flucloxacillin

  b

  Ciprofloxacin and flucloxacillin

  c

  Flucloxacillin and metronidazole

  d

  Clarithromycin and metronidazole

  e

  Amoxicillin and clarithromycin
  Explanation: The "usual" organisms to cause cellulitis are Streptococcus species and Staphylococcus aureus. High dose flucloxacillin would be sufficient for this purpose. Given the history of freshwater contact, Aeromonas species are ubiquitously present in fresh water and are opportunistic human pathogens (A. hydrophila being the species most commonly identified). Ciprofloxacin would cover this. The combination of flocloxacillin and ciprofloxacin is recommended by NICE for cellulitis following freshwater contact. A. Does not cover Aeromonas species. B. The correct answer. C–E. None of these regimens cover Aeromonas species.
• 51
  You are a junior doctor in the medical admissions unit of a busy district general hospital. A 53-year-old man has been referred in by his GP for infected foot ulcers. On closer questioning, he tells you that he has had these ulcers now for two years, but they have only “got bad” in the last two weeks. His GP prescribed seven days of oral flucloxacillin, but the infection is worse, not better, and has therefore referred him in for intravenous antibiotic therapy. On removing the bandages, you discover a foul-smelling circumferential ulcer oozing a green exudate. What antibiotics might you prescribe?
  Difficulty: Easy     Topic: Common infections
  a

  Flucloxacillin

  b

  Co-amoxiclav (Augmentin®)

  c

  Piperacillin-tazobactam (Tazocin®)

  d

  Clindamycin

  e

  Erythromycin
  Explanation: The current NICE guidelines for the management of diabetic feet (2004) do not make any specific recommendations for the management of infected diabetic foot ulcers. The foul smell suggests anaerobic infection, while the green exudate suggests infection (or at least colonisation by) Pseudomonas aeruginosa. You should still consider cover for Gram-positives (Streptococcus species and Staphylococcus aureus). A. Flucloxacillin covers Gram-positives, but does not cover anaerobes or Pseudomonas. B. Co-amoxiclav covers Gram-positives and anaerobes, but does not cover Pseudomonas. C. The correct answer. Piperacillin-tazobactam covers Streptococcus species, Staphylococcus aureus, Pseudomonas aeruginosa and anaerobes. D. Clindamycin covers the Gram-positives and anaerobes, but not Pseudomonas. E. Erythromycin covers the Gram-positives but not anaerobes or Pseudomonas.
• 52
  You are a junior doctor on a surgical ward. An 83-year-old woman had a hip replacement three days ago for a fractured neck of femur. The wound is now erythematous and oozing pus. What antibiotic would you start?
  Difficulty: Medium     Topic: Common infections
  a

  Vancomycin

  b

  Co-amoxiclav (Augmentin®)

  c

  Piperacillin-tazobactam (Tazocin®)

  d

  Flucloxacillin

  e

  Refer to microbiology or infectious diseases for advice
  Explanation: The antibiotic choice depends on local patterns of resistance, which will be different at each hospital. No general recommendation can be made and the involvement of a specialist is mandatory (microbiology or infectious diseases). In this particular instance, the prosthetic hip is also likely to be involved. Do not start empirical antibiotics without first obtaining advice as to what samples to collect for microbiology: these will probably be intra-operative samples and should be collected off antibiotics. It is almost certain that repeated surgery will be necessary to drain any collections, debride the infected material or remove the infected prosthesis.
• 53
  You are a junior doctor in the accident and amergency department. A 53-year-old man comes to you with a fever and a painful swollen leg. He returned yesterday from a snorkelling holiday in the Caribbean and thinks he cut his leg on some coral. On examination, he is febrile 38.2°C, confused and tachycardic 106 beats/min, but his blood pressure is normal. His leg is erythematous and oedematous with multiple large bullae. Microscopy of fluid from a bulla shows curved Gram-negative bacilli. What is the causative organism?
  Difficulty: Hard     Topic: Common infections
  a

  Streptococcus pyogenes

  b

  Staphylococcus aureus

  c

  Escherichia coli

  d

  Vibrio vulnificus

  e

  Mycobacterium marium
  Explanation: This man is septic with an aggressive cellulitis. The history of salt water exposure suggests that the causative organism is the Gram-negative bacillus, Vibrio vulnificus, which is found in warm surface seawater worldwide. Culture of fluid from one of the bullae or from blood is often helpful. V. vulnificus is usually susceptible to doxycycline, ciprofloxacin, third-generation cephalosporins (e.g., ceftazidime, cefotaxime) and carbapenems. Until the infecting organism is known, empirical antibiotic therapy should still also cover the usual Gram-positive organisms which cause cellulitis (Streptococcus species and Staphylococcus aureus). Cellulitis due to V. vulnificus can progress rapidly to necrotising fasciitis: controlling the infection means aggressively debriding any necrotic tissue and limb amputation is sometimes necessary. It is not unusual for patients to require vasopressor support and renal replacement therapy in an intensive care setting. A. It would be unusual for S. pyogenes to cause bullae, but it can do when it causes necrotising fasciitis and causes the epidermis to lift off the necrotic skin below. However, the history of seawater contact suggests an alternative diagnosis. B. S. aureus can fulminant, aggressive disease and it does characteristically cause blistering with a golden crust, but large bullae are not typical. S. aureus is not usually associated with a history of seawater contact. C. E. coli would be an unusual cause of cellulitis. D. The correct answer. E. M. marinum is associated with seaswater contact, but it is not a cause of acute fulminant disease. Instead, it causes small, localised lesions ("Fish tank granuloma") that progress over many weeks.
• 54
  Which of the following antimicrobials does not act on the bacterial cell wall?
  Difficulty: Easy     Topic: Common infections
  a

  Erythromycin

  b

  Benzylpenicillin

  c

  Ceftriaxone

  d

  Vancomycin

  e

  Meropenem
  Explanation: As a rule, antimicrobial agents that target the bacterial cell wall are bactericidal (they kill the bacterium directly). Antibiotics that merely stop the bacteria from replicating, but do not kill them, care called 'bacteriostatic'. Bactericidal antibiotics are preferred in patients who are severely immunocompromised (e.g., neutropaenic patients, who are deficient in white cells), abscesses and collections (where white cells cannot penetrate) and endocarditis (again, white cells do not penetrate to the centre of the vegetation). A. Erythromycin (in common with all macrolides) blocks protein synthesis by binding to the 50s subunit of the bacterial ribosome. B, C, E. All beta-lactams work by preventing peptidoglycan cross-linking in the bacterial cell wall. The three major classes of beta-lactams are the penicillins, the cephalosporins and the carbapenems.
• 55
  Which of the following antimicrobials does not target the bacterial ribosome?
  Difficulty: Easy     Topic: Common infections
  a

  Erythromycin

  b

  Chloramphenicol

  c

  Doxycycline

  d

  Gentamicin

  e

  Ciprofloxacin
  Explanation: A, B. The macrolides (including erythromycin) and chloramphenicol target the 50S ribosomal subunit (although the exact binding sites are different). C, D. The tetracyclines (including doxycycline) and the aminoglycosides (including gentamicin) bind to the 30S ribosomal subunit. Antimicrobials that inhibit protein synthesis are bacteriostatic (they only stop the bacterium from replicating), not bactericidal (they do not kill the bacterium). The aminoglycosides are the exception: they have a second site of action, which is the outer membrane of Gram-negative bacteria. Generally speaking, they are therefore bactericidal against Gram-negatives, but bacteristatic against Gram-positives. E. The fluoroquinolones (including ciprofloxacin) target DNA synthesis.
• 56
  Which of the following are AIDS-defining conditions?
  Difficulty: Easy     Topic: HIV
  a

  Tuberculosis

  b

  Pneumocystis jirovecii pneumonia

  c

  Kaposi's sarcoma

  d

  Cryptococcal meningitis

  e

  All of the above
  Explanation: An AIDS-defining condition is a disease which in a patient with HIV infection, leads to a definition of AIDS and should prompt initiation of treatment for HIV regardless of CD4 count. The presence of an AIDS-defining illness in any patient not known to have HIV should prompt immediate testing for HIV. Note that in patients not known to have HIV, the prevalence of HIV differs enormously within populations: for example, of patients with tuberculosis in many parts of sub-Saharan Africa, around half have HIV. By contrast, of patients with tuberculosis in sub-Saharan Africa, <5% have HIV. Other immunosuppressive conditions (e.g., organ transplant) may also predispose to the development of an AIDS-defining condition and does not necessarily mean that the patient has AIDS. A–D. These are all AIDS-defining illnesses. E. The correct answer.
• 57
  Which of the following are AIDS-defining conditions?
  Difficulty: Medium     Topic: HIV
  a

  Cerebral toxoplasmosis

  b

  Non-Hodgkin's lymphoma

  c

  Cervical carcinoma

  d

  Cytomegalovirus retinitis

  e

  All of the above
  Explanation: An AIDS-defining condition is a disease which in a patient with HIV infection, leads to a definition of AIDS and should prompt initiation of treatment for HIV regardless of CD4 count. The presence of an AIDS-defining illness in any patient not known to have HIV should prompt immediate testing for HIV. Note that in patients not known to have HIV, the prevalence of HIV differs enormously within populations: for example, of patients with tuberculosis in many parts of sub-Saharan Africa, around half have HIV. By contrast, of patients with tuberculosis in sub-Saharan Africa, <5% have HIV. Other immunosuppressive conditions (e.g., organ transplant) may also predispose to the development of an AIDS-defining condition and does not necessarily mean that the patient has AIDS. A–D. These are all AIDS-defining illnesses. E. The correct answer.
• 58
  Which of the following cells are the primary target of the human immunodeficiency virus (HIV)?
  Difficulty: Easy     Topic: HIV
  a

  CD4-positive T-lymphocytes

  b

  CD8-positive T-lymphocytes

  c

  CD56-positive natural killer (NK) cells

  d

  Neutrophil polymorphs

  e

  CD19-positive B-lymphocytes
  Explanation: A. The correct answer. HIV targets the CD4 receptor. Monocytes are also CD4 positive and are infected by HIV. B–E. None of these cells express the CD4 receptor on their surface.
• 59
  Which one of the following vaccines are contra-indicated in patients with HIV and a CD4 count <200 cells/mm3?
  Difficulty: Easy     Topic: HIV
  a

  Hepatitis B

  b

  Seasonal Influenza

  c

  Bacille de Calmette-Guérin (BCG)

  d

  Hepatitis A

  e

  Tetanus-diphtheria/parenteral polio virus (Td/IPV)
  Explanation: Inactivated or subunit vaccines are generally safe in HIV (although they may be less effective). Some live vaccines can be used provided the CD4 count is >200. A. The hepatitis B vaccine consists only of recombinant s-antigen generateed from yeast cells, not whole virus, and is therefore incapable of causing infection. B. All but one of the seasonal influenza vaccines licensed in the UK contains only inactivated virus. Live influenza vaccine is contra-indicated in HIV infection regardless of CD4 count. C. The correct answer. BCG is a live vaccine and is capable of causing disseminated disease in the immunocompromised. It is contra-indicated in HIV regardless of CD4 count. Patients should be considered for latent TB screening and treatment instead. D. All hepatitis A vaccines licensed in the UK are inactivated. E. This is not a live vaccine and is safe to give in HIV infection regardless of CD4 count.
• 60
  Which one of the following vaccines is contra-indicated in patients with HIV and a CD4 count <200 cells/mm3?
  Difficulty: Medium     Topic: HIV
  a

  Haemophilus influenzae type b

  b

  Yellow fever

  c

  Hepatitis A

  d

  Hepatitis B

  e

  Rabies
  Explanation: A. The vaccine contains capsular polysaccharide only, not whole bacteria. B. The correct answer. The yellow fever vaccine is a live, attenuated virus. It is offered to travellers to South America and sub-Saharan Africa. Many countries require a certificate of yellow fever vaccination before issuing a visa. Patients with a CD4 count <200 should be advised not to travel to these countries. It may safely be given once the CD4 count has risen above 200. C. All hepatitis A vaccines licensed in the UK are inactivated and cannot cause infection. D. The hepatitis B vaccine consists only of recombinant s-antigen generateed from yeast cells, not whole virus and is therefore incapable of causing infection. E. The rabies vaccines licensed in the UK consist of inactivated virus and therefore cannot cause disease.
• 61
  Which of the following vaccines may not be given to patients with HIV infection and a CD4 count >200 cells/mm3?
  Difficulty: Hard     Topic: HIV
  a

  Bacille de Calmette-Guérin (BCG)

  b

  Yellow fever

  c

  Measles, mumps, rubella (MMR)

  d

  Hepatitis A

  e

  Hepatitis B
  Explanation: The following live vaccines cannot be given to a patient with HIV regardless of CD4 count: BCG, live cholera, smallpox. A. BCG is a live vaccine and is capable of causing disseminated disease in the immunocompromised. It is contra-indicated in HIV regardless of CD4 count. Patients should be considered for latent TB screening and treatment instead. B. The yellow fever vaccine is a live, attenuated vaccine. It can be given to HIV patients with a CD4 count >200, but not below. C. The MMR vaccine is a live attenuated vaccine. It can also be given to HIV patients with a CD4 count >200, but not below. D. All the hepatitis A vaccines licensed in the UK are inactivated virus. E. The hepatitis B vaccine consists only of recombinant s-antigen generateed from yeast cells, not whole virus, and is therefore incapable of causing infection.
• 62
  In the UK, which of the following risk groups has the lowest estimated prevalence of HIV?
  Difficulty: Medium     Topic: HIV
  a

  Injecting drug users (in London)

  b

  Injecting drug users (outside London)

  c

  Women born in sub-Saharan Africa

  d

  Men who has sex with men (in London)

  e

  Men who has sex with men (outside London)
  Explanation: HIV prevalence in the UK is 0.5–0.1%, but varies widely by region. A. The prevalence of HIV in injecting drug users (IVDU) in London is estimated to be 0.9%. B. The correct answer. Estimated prevalence 0.4% in IVDUs outside London. C. 6.2% in women born in sub-Saharan Africa. D. 8.1% in MSMs in London. E. 3.1% in MSMs outside of London.
• 63
  Which of the following exposures has the highest risk of transmission from an individual known to have HIV?
  Difficulty: Easy     Topic: HIV
  a

  Needlestick injury

  b

  Blood transfusion

  c

  Receptive vaginal intercourse

  d

  Insertive vaginal intercourse

  e

  Sharing injecting equipment
  Explanation: Risks stated here do not take into account the effect post-exposure prophylaxis. A. The estimated risk of transmission 0.3% per needlestick. B. The correct answer. Estimated risk is 90–100%. C. Receptive vaginal intercourse (i.e., risk to the woman) estimated risk 0.1%. D. Insertive vaginal intercourse (i.e., risk to the man) 0.082%. E. Estimated risk from sharing needles is 0.67%. It is important to note that each risk is estimated per exposure. For example, the estimated risk of transmission to a woman from a single act of receptive vaginal intercourse is 0.1%. However, if she has sex three times a week for a year, you can calculate her cumulative risk over the year to be 14.5%.
• 64
  Which of the following exposures has the lowest risk of transmission from an individual known to have HIV?
  Difficulty: Medium     Topic: HIV
  a

  Insertive anal intercourse

  b

  Receptive anal intercourse

  c

  Insertive vaginal intercourse

  d

  Receptive vaginal intercourse

  e

  Receptive oral intercourse
  Explanation: A. Insertive anal intercourse carries an estimated risk of 0.06% per exposure. B. 1.11% for receptive anal intercourse. C. 0.082% for insertive vaginal intercourse. D. 0.1% for receptive vaginal intercourse. E. The corect answer. 0.02% for receptive oral sex. It is sometimes erroneously believed that oral sex carries no risk of HIV transmission. While the risk is smaller than with vaginal or anal sex, the risk is still measurable. However, the risk from insertive oral sex is believed to be too small to measure.
• 65
  A 34-year-old man presents with a two-month history of dry cough and worsening breathlessness. He is normally fit and well with no history of recent travel. His oxygen saturation on pulse oxymetry is 96% on air, but after walking up and down the corridor, his saturations are only 86%. The chest radiograph shows fine bilateral reticular shadowing with a perihilar distribution. What should you do next?
  Difficulty: Hard     Topic: HIV
  a

  Start intravenous benzylpenicillin and clarithromycin.

  b

  Start high dose steroids.

  c

  Perform an HIV test.

  d

  Send sputum for culture.

  e

  Request computed tomography (CT) of the thorax.
  Explanation: The patient has pneumocystis pneumonia (commonly called PCP) and undiagnosed HIV. PCP is the most common AIDS-defining illnesses after oesophageal candidiasis. The organism cannot be cultured, and the diagnosis is made by PCR of washings collected on bronchoscopy, which is not part of the standard work-up for pneumonia and will normally only be done after the diagnosis of Hiv is made. The key to the diagnosis therefore is clinical suspicion (risk factors for HIV can be helpful, but >20% of HIV patients do not have any recognised risk factor and an even larger proportion have risk factors identified only after diagnosis with HIV). Treatment for HIV and for pneumocystis pneumonia should be started in consultation with an infectious diseases specialist. All HIV patients with a CD4 count <200 cells/mm3 should be offered co-trimoxazole chemoprophylaxis to prevent. A. This combination of antibiotics would be suitable for the empirical treatment of community-acquired pneumonia. B. Steroid are often used to treat interstitial lung disease, which early PCP can mimic. C. The correct answer. None of the diagnostic tests for PCP would be performed without first making a diagnosis of HIV. D. Pneumocystis jiroveciii cannot be cultured. E. CT may show patches of ground glass shadowing and cysts within the lungs. These findings are characteristic of PCP, but are not diagnostic. An HIV test is still needed first.
• 66
  Which one of the following organisms does not cause tuberculosis?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Mycobacterium leprae

  b

  Mycobacterium africanum

  c

  Mycobacterium bovis

  d

  Mycobacterium canetti

  e

  Mycobacterium tuberculosis
  Explanation: A. The correct answer. M. leprae causes leprosy. B–E. These are all causes of tuberculosis. The vast majority of cases worldwide are caused by M. tuberculosis. M. bovis (bovine tuberculosis) used to be a common cause of tuberculosis prior to the pasteurisation of milk. Infection of badgers and cattle is still a problem in most parts of Europe. M. africanum is largely confined to West and Central Africa and migrants from those places. M. canetti infection is largely confined to the Horn of Africa.
• 67
  You are a junior doctor in the acute medical unit. A 32-year-old man presents with a two-month history of fever, cough, and 5 kg weight-loss. He is not a smoker and has no significant medical history. On examination, he is thin, but the remainder of the clinical examination is normal. Urgent sputum microscopy shows acid-fast bacilli in his sputum. What treatment would you start?
  Difficulty: Easy     Topic: Tuberculosis
  a

  Isoniazid, rifampicin, moxifloxacin and streptomycin

  b

  Streptomycin, moxifloxacin, pyrazinamide and ethambutol

  c

  Rifampicin, moxifloxacin, pyrazindamide and ethambutol

  d

  Isoniazid, rifampicin, pyrazinamide and ethambutol

  e

  Isoniazid, rifampicin, pyrazinamide and streptomycin
  Explanation: The patient has smear-positive pulmonary tuberculosis. The standard regimen in the UK is isoniazid, rifampicin and pyrazindamide (combined preparation Rifater®). Ethambutol is also added, because isoniazid resistance is 5% or higher in most parts of the UK.Treatment is reviewed after two months and simplified to isoniazid and rifampicin only (Rifinah®) for a further four months if the isolate is fully-sensitive. Some physicians add pyridoxine (vitamin B6) to reduce the risk of developing isoniazid-related peripheral neuropathy. Moxifloxacin is useful for second-line treatment of multidrug resistant TB. Streptomycin is not often used first-line because it must be given by intramuscular injection, and is associated with vestibulocochlear and renal toxicity: it was discovered in 1946; the first ever treatment for TB.
• 68
  You are a GP. A 32-year-old man presents with a two-month history of fever, cough, and 5 kg weight-loss. He is not a smoker and has no significant medical history. On examination, he is thin, but the remainder of the clinical examination is normal. What is the diagnostic investigation?
  Difficulty: Easy     Topic: Tuberculosis
  a

  Chest radiograph

  b

  Sputum examination

  c

  Interferon gamma-release assay (T-SPOT.TB® or Quantiferon®)

  d

  Full blood count

  e

  Mantoux test
  Explanation: Tuberculosis is Mycobacterium tuberculosis infection. Diagnosis is therefore by isolation and identification of M. tuberculosis in a clinical specimen. A. Chest X-ray is useful for determining the extent of the disease, but is not dagnostic. B. Sputum microscopy for acid-fast bacilli (AFB) can give a same-day diagnosis. Culture is still required for confirmation. C. IGRAs have only been evaluated for the diagnosis of latent tuberculosis, not active tuberculosis. D. The neutrophil count may be elevated and the lypnhocytes count may be low. However, this finding is not always present (the white cell count can be completely normal in tuberculosis) and even if it is present, it is not specific to TB, but is present in any cause of acute systemic inflammation. E. Like the IGRAs, the Mantoux test has only been validated for the diagnosis of latent tuberculosis. It has little role to play in the diagnosis of active tuberculosis.
• 69
  You are a GP. A 32-year-old man presents with a two-month history of a lump on the right side of his neck. He also complains of fever, drenching night sweats and 5 kg weight-loss over roughly the same period. On examination, he is thin, with a 4 cm mass of matted fixed lymph nodes in the right posterior cervical triangle. What is the diagnostic investigation?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Lymph node biopsy

  b

  Sputum examination

  c

  Interferon gamma-release assay (T-SPOT.TB® or Quantiferon®)

  d

  Chest radiograph

  e

  Mantoux test
  Explanation: Lymphoma and lymph node tuberculosis are indistinguishable clinically. The only way to distinguish between the two is surgical biopsy of the lymph node mass: half the sample should be sent for histology and the other half should be sent for mycobacterial culture. Lymph node aspiration for cytology and mycobacterial culture can make the diagnosis, but does not do so reliably, because the sample size is so small. A. The correct answer. B. Without any chest symptoms, sputum examination is unlikely to be useful. C. IGRAs have only been evaluated for the diagnosis of latent tuberculosis, not active tuberculosis. D. The chest radiograph may show pulmonary tuberculosis, or it may show mediastinal lymph node enlargement. However, no definitive diagnosis can be made by radiography. E. Like the IGRAs, the Mantoux test has only been validated for the diagnosis of latent tuberculosis. It has little role to play in the diagnosis of active tuberculosis.
• 70
  You are a GP. A 64-year-old Pakistani woman presents with fever and dysuria. You perform a urine dipstick and it is positive for leukocytes, blood and protein. This is the fourth time she is presenting to you with these symptoms. You have given her a course of trimethoprim and a course of cephalexin to date, but she reports only transient benefit. Three previous midstream urine (MSU) samples confirmed the presence of pus in the urine, but failed to grow any pathogens. What is the diagnostic investigation?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Repeat the midstream urine culture.

  b

  Send early morning urine for culture.

  c

  Request an ultrasound (US) of the renal tract.

  d

  Request computed tomography (CT) of the renal tract.

  e

  Urine microscopy for AFB
  Explanation: This woman has 'sterile' pyuria, for which tuberculous pyelonephritis should always be in the differential diagnosis (however, bear in mind that the most common cause of sterile pyuria is E. coli UTI with the MSU collected after antibiotics have been started). A. Midstream urines are processed for common uropathogens such as Escherichia coli, Klebsiella species and Proteus species. They are never processed for TB culture and routine culture will not pick up M. tuberculosis. B. The correct answer. C. Ultrasound is useful mainly for identifying obstruction, masses and collections. Ultrasound cannot provide a diagnosis. D. CT is useful for identifying perfusion defects obstruction, localising stones, identifying masses, collections and gas bubbles. Like all other imaging modalities, CT may provide a list of differential diagnoses, but it cannot definitively identify the causative organism. E. Urine microscopy is of little value in the diagnosis of TB. This is because urine is frequently contaminated by environmental mycobacteria that will be AFB positive. These are indistinguishable from M. tuberculosis under the microscope.
• 71
  You are a GP. A 64-year-old Pakistani woman presents with a three-month history of fever, weight loss and back pain. She thinks that the back pain is muscular from carrying her 2-year-old grandchild. On examination, she is thin, but apyrexial. there is bony tenderness at the level of the 10th thoracic vertebra. She has no neurological deficits. What investigation should you perform next?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Plain radiograph of the thoracic spine.

  b

  Re-assure her that the examination is normal and send her home.

  c

  Magnetic resonance imaging (MRI) of the thoracic spine.

  d

  Refer to physiotherapy.

  e

  Review again in a month to see if neurological signs appear to help localise the lesion.
  Explanation: A. A plain radiograph is useful for diagnosing fractures, but since there is no history of trauma, it is of no value whatsoever and represents an unnecessary dose of radiation. B. The examination is not normal. Unexplained weight loss is a sinister symptom. C. The correct answer. MRI will not provide the diagnosis, but it will identify any abscesses or masses. A biopsy of any abnormality (probably by a spinal surgeon) will still be needed to make a diagnosis. the differential includes a chronic abscess (e.g., tuberculosis) or malignancy. D. Given the presence of a possible erosive lesion to the spine, physiotherapy carries with it the risk of pathological fracture. E. If there is a lesion potentially threatening the spine, then it is negligent to wait.
• 72
  Which of the following is a risk factor for tuberculosis?
  Difficulty: Easy     Topic: Tuberculosis
  a

  HIV infection

  b

  Diabetes mellitus

  c

  Malnutrition

  d

  End-stage renal failure

  e

  All of the above
  Explanation: A. HIV increases the risk of TB by 25–75 times and is one of the most important risk factors worldwide. B. Diabetes increasees the risk by 2–4 times and is one of the most common risk factors worldwide. C. Malnutrition increases the risk of TB, while obesity is protective. D. Patients on haemodialysis have a 10–15 fold risk of TB. E. The correct answer.
• 73
  Which of the following is a risk factor for tuberculosis?
  Difficulty: Easy     Topic: Tuberculosis
  a

  HIV infection

  b

  Jejunoileal bypass

  c

  Silicosis

  d

  Smoking

  e

  All of the above
  Explanation: A. HIV infection increases the risk of TB by 25–75 fold and is one of the most important risk factors worldwide. B. Jejunoileal bypass surgery increases the risk of TB by 30–60 times. C. Silicosis increases the risk by about 30 fold. D. Smoking >20 packets/day increases the risk 2–3 fold. E. The correct answer.
• 74
  Which of the following is a risk factor for tuberculosis?
  Difficulty: Easy     Topic: Tuberculosis
  a

  Diabetes mellitus

  b

  Age

  c

  Carcinoma

  d

  Coal mining

  e

  All of the above
  Explanation: A. Diabetes increasees the risk by 2–4 times and is one of the most common risk factrors worldwide. B. In endemic populations (e.g., India), the highest incidence is in young adults (25–35) and declining thereafter. In populations that were previously endemic (e.g., Ireland), the highest incidence is in the elderly who were exposed in adolescence or early adulthood. C. All cancers are associated with an increased risk of up to 16 fold. D. Occupational exposure to dust (silicosis, pneumoconiosis, etc.) increases the risk about 30 fold. E. The correct answer.
• 75
  A 56-year old woman with atrial fibrillation presents with sudden onset dense left-sided hemi-paresis and hemi-sensory loss that persists for 3-hours. She has a background of idiopathic atrial fibrillation, type 2 diabetes, and has recently started treatment for tuberculosis. She takes: gliclazide, metformin, digoxin, warfarin, isoniazid, rifampicin, ethambutol, pyrazinamide, and pyridoxine. Which of her medications is most likely to have caused this presentation?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Gliclazide

  b

  Metformin

  c

  Digoxin

  d

  Isoniazid

  e

  Rifampicin
  Explanation: This woman has had a thromboembolic stroke secondary to her atrial fibrillation. Rifampicin (called rifampin in the US) is part of the standard four-drug regimen for tuberculosis. It increases the clearance of many drugs and the interaction between rifampicin and warfarin is particularly dangerous: rifampicin would reduce the effect of warfarin so that she is no longer adequately anticoagulated and therefore at risk of thromboembolic strokes secondary to the AF. A. The most common side effect of gliclazide is hypoglycaemia. Hypoglycaemia can rarely cause hemipareses mimicking a stroke. Rifampicin may however reduce the effect of gliclazide leading to hyperglycaemia, not hypoglycaemia. B. The most dangerous adverse effect of metformin is lactic acidosis. C. Digoxin may be less effective when given with rifampicin. This would manifest as tachycardia, not as a stroke. D. Isoniazid can cause peripheral neuropathy and hepatitis. E. The correct answer.
• 76
  You are a junior doctor in the accident and emergency department. A 34-year-old woman attends the department complaining of blood in her eyes and urine. She started treatment for lymph node tuberculosis two days ago. On examination, her tears are reddish-orange and her contact lenses have been stained orange. Her urine is also reddish-orange but dipstick examination shows no blood. What should you do next?
  Difficulty: Easy     Topic: Tuberculosis
  a

  Perform an urgent clotting screen.

  b

  Cross match four units of blood immediately.

  c

  Insert two large bore cannulae and start immediate fluid resuscitation.

  d

  Re-assure her and discharge.

  e

  Place the patient in a side room immediately with full isolation precautions.
  Explanation: Rifampicin will colour all bolidy secretions (tears, sweat, urine) a reddish-orange colour. This is completely harmless. Contact lenses, however, will be permanently stained. A–C. There is no clinical evidence of abnormal bleeding. D The correct answer. E. Spontaneous bleeding from the the eyes and in the urine are signs of viral hamorrhagic fever, however, in this instance, the patient appears to have mistaken the colouration of rifampicin in her bodily secretions for blood.
• 77
  You are a GP. A 64-year-old Pakistani woman presents with one week of pains and needles in her fingers and toes. She was started on treatment for pulmonary tuberculosis three weeks ago by the chest physician at the local district general hospital with standard four-drug therapy. What drug is most likely responsible for her symptoms?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Isoniazid

  b

  Rifampicin

  c

  Pyrazinamide

  d

  Ethambutol

  e

  Streptomycin
  Explanation: A common adverse effect of isoniazid is peripheral neuropathy, which is consistent with the symptoms this woman is describing. The treatment is to stop the isoniazid and administer vitamin B6 at high doses. Stopping the isoniazid should only be done in consultation with the physician managing her TB, because it will be important to find an alternative, which means non-standard TB regimens will be used. Other important side effects of isoniazid are hepatitis (2–3%), lupus-like reactions (1%) and red cell aplasia (very rare).
• 78
  You are a junior doctor in the accident and emergency department. A 34-year-old woman attends the department complaining of pain in the joints of all four limbs. The pain is severe enough that it is stopping her from going to work. Even at home, she has to go up and down the stairs at home on her bottom because she cannot walk. She was started on treatment for lymph node tuberculosis three weeks ago with standard four-drug therapy. Clinical examination of her joints is normal. What drug is most likely to be responsible?
  Difficulty: Hard     Topic: Tuberculosis
  a

  Isoniazid

  b

  Rifampicin

  c

  Pyrazinamide

  d

  Ethambutol

  e

  Streptomycin
  Explanation: Joint pain (arthralgia) is a common side effect of pyrazinamide treatment, although it is rare for the pain to be as severe as this. Clinical examination is usually normal. Pyrazinamide also increases levels of uric acid in the blood, and can precipitate attacks of gout in patients susceptible to it (this is not what this patient has, since gout is oligoarticular and there would be clinical signs of joint swelling and erythema). Note that pyrazinamide arthralgia and gout are separate clinical syndromes. The most important adverse effect of pyrazinamide treatment is hepatitis.
• 79
  You are a GP. A 64-year-old Pakistani woman presents with a one week of vomiting. On examination, she is clinically jaundiced. Her bilirubin is 120 and ALT 839. She was started on treatment for pulmonary tuberculosis three weeks ago by the chest physician at the local district general hospital with standard four-drug therapy. What should you do next?
  Difficulty: Medium     Topic: Tuberculosis
  a

  Stop isoniazid

  b

  Stop rifampicin

  c

  Stop pyrazinamide

  d

  Stop ethambutol

  e

  Stop all tuberculosis medication
  Explanation: This woman has drug-induced hepatitis. The most likely culprit (in descending order of probability) is pyrazinamide, followed by isoniazid, then rifampicin. Hepatitis due to ethambutol is rare (if it does cause liver problems, it tends to be cholestatic jaundice). It is not possible to determine clinically which drug is causing the problem and because drug-induced hepatitis is potentially fatal, all the drugs should be stopped immediately. When her medication is restarted, it will have to be reintroduced one by one over a number of days.
• 80
  Which of the following species are recognised causes of malaria in man?
  Difficulty: Medium     Topic: -
  a

  Plasmodium falciparum

  b

  Plasmodium malariae

  c

  Plasmodium ovale

  d

  Plasmodium vivax

  e

  Plasmodium yoelii
  Explanation: A-B. P. falciparum, P. malariae, P. ovale and P. vivax are all recognised causes of malaria in humans. There is a fifth species more recently described in Borneo called P. knowlesi. E. P. yoelii is capable of causing malaria in mice and is an important animal model of human malaria.
• 81
  You are a junior doctor in accident and emergency. An 18-year-old medical student presents with a two-day history of fever. He returned five days ago from a three-month elective to Malawi. He is normally fit and well. On examination, he has a fever of 39.3°C, but the rest of the clinical examination is normal. An urgent blood film shows numerous thin intracellular ring-forms in his erythrocytes. What is the diagnosis?
  Difficulty: Easy     Topic: Tropical diseases
  a

  Plasmodium falciparum infection

  b

  Plasmodium vivax infection

  c

  Salmonella enterica var Typhi infection

  d

  Babesia microti infection

  e

  Schistosoma mansoni infection
  Explanation: The patient has falciparum malaria. The blood film typically shows numerous ring-shaped early trophozoites of Plasmodium falciparum. Malaria is a notifible disease in the UK. A. The correct answer. B. The trophozoites (young parasites) of vivax malaria are characteristically "amoeboid" in shape, and the parasitized erythrocytes have multiple blue dots called "Schuffner's dots". The young trophozoite of P. vivax can look like P. falciparum, but they are not usually multiple. C. Salmonella causes a bacterial infection. A blood film might show a neutrophilia and left-shift, but the pathogen is not usually visible. D. Babesia can indeed produce ring forms, but Babesiai is not native to Malawi. E. Schistosoma parasites are not normally visible on a peripheral blood film. Instead the parasites are found in the hepatic portal system.
• 82
  You are a junior doctor in accident and emergency. An 18-year-old medical student presents with a two-day history of fever. He returned five days ago from a three-month elective to Malawi. He is normally fit and well. On examination, he has a fever of 39.3°C, but the rest of the clinical examination is normal. An urgent blood film shows ring forms in his red blood cells. What treatment should you offer?
  Difficulty: Easy     Topic: Tropical diseases
  a

  Intravenous quinine

  b

  Oral co-artem (artemether-lumefantrine)

  c

  Azithromycin

  d

  Oral quinine

  e

  Sulphadoxine-pyrimethamine (Fansidar® or SP)
  Explanation: The patient has uncomplicated falciparum malaria. There are no severe features, so the 2012 WHO guidelines (the 2007 UK guidelines are out-of-date) recommend oral artemesinin combination therapy (of which the only one licensed in the UK and US is co-artem). Malaria is a notifible disease in the UK. A. Quinine is associated with a slower response and has more side effects (hypoglycaemia, cardiac arrhythmia and tinnitus being the main side effects). B. The correct answer. C. Azithromycin has no proven clinical efficacy in malaria, although there is in vitro evidence it may work (Ohrt Antimicrob Agents Chemother 2002). D. Poorly tolerated and proven to be inferior to co-artem. Quinine used to be first-line therapy but has since been superseded by the artemesinins. E. Resistance is common and it should no longer be used.
• 83
  You are a junior doctor in accident and emergency. An 18-year-old medical student presents with a two-day history of fever. He returned five days ago from a three-month elective to Malawi. He is normally fit and well. On examination, he has a fever of 39.3°C, his heart rate is 124, his blood pressure is 80/40 and he is clinically jaundiced. He has a creatinine of 140 µmol/l and bilirubin of 54 µmol/l. An urgent blood film shows ring forms in his red blood cells. What treatment should you offer?
  Difficulty: Medium     Topic: Tropical diseases
  a

  Refer immediately to infectious diseases

  b

  Oral co-artem (artemether-lumefantrine)

  c

  Azithromycin

  d

  Oral quinine

  e

  Sulphadoxine-pyrimethamine (Fansidar® or SP)
  Explanation: The patient has severe falciparum malaria (clinical jaundice). Severe malaria is defined as any one of the following: imparied consciousness, convulsions, systolic blood pressure <70 mmHg in adults, clinical jaundice, pulmonary oedema, or creatinine >265 µmol/l. The reader should refer to the 2012 WHO guidelines for a complete list. Intravenous artesunate is first-line treatment for severe malaria. Malaria is a notifible disease in the UK. A. The correct answer. Unfortunately, artesunate is not licensed in the UK and is therefore not stocked by most UK hospitals. It is however obtainable from most tropical medicine units in the UK who will be contactable via the local infectious diseases service. If IV artesunate is not available, then the on-call ID physician may ask you to start IV quinine until artesunate can be obtained. B. Oral therapy is only suitable for uncomplicated malaria. If IV artesunate cannot be obtained quickly, it may be appropriate to start co-artem if that is immediately available and the patient is able to take oral medication. C. Azithromycin has no proven clinical efficacy in malaria, although there is some in vitro evidence it may work (Ohrt Antimicrob Agents Chemother 2002). D. Oral quinine should not be used in severe malaria unless there is no alternative. The 2007 UK guidelines recommended intravenous quinine as first line treatment, but were superseded by the 2010 WHO guidelines. E. Resistance is common and SP should no longer be used.
• 84
  You are a junior doctor in accident and emergency. An 18-year-old medical student presents with a two-day history of fever. He returned five days ago from a three-month elective to India. He is normally fit and well. On examination, he has a fever of 39.3°C, but the rest of the clinical examination is normal. An urgent blood film shows large amoeboid trophozoites within enlarged erythrocytes. Schuffner’s dots are visible. What is the diagnosis?
  Difficulty: Medium     Topic: Tropical diseases
  a

  Plasmodium falciparum infection

  b

  Plasmodium vivax infection

  c

  Salmonella enterica var Typhi infection

  d

  Babesia microti infection

  e

  Schistosoma mansoni infection
  Explanation: The patient has vivax malaria. This is usually benign and unlike falciparum malaria, is still usually susceptible to chloroquine treatment. The large amoeboid trophozoite with Schuffner's dots is characteristic of the species. Vivax is the dominant malaria species outside of Africa. A. In falciparum malaria, late stage trophozoites are not normally seen in the blood film. B. The correct answer. C. The blood film in typhoid may show neutrophilia and a left shift, but it is not usual to see the infecting organism. D. Babesia microti is endemic to North America. E. Schistosoma parasites are not normally visible in peripheral blood films.
• 85
  You are a junior doctor in a district general hospital. An 18-year-old medical student presents with a two-day history of fever. He returned five days ago from a three-month elective to India. A diagnosis of vivax malaria is made on the blood film. There is no evidence of any complications What treatment do you recommend?
  Difficulty: Medium     Topic: Tropical diseases
  a

  Chloroquine

  b

  Chloroquine and primaquine

  c

  Quinine

  d

  Co-artem

  e

  Quinine and doxycycline
  Explanation: When a human is first infected with malaria, the first cells to be infected are those of the liver, not the blood. In vivax malaria, some of these parasites form a latent stage in the liver, called hypnozoites. These hypnozoites may cause relapses weeks and months later. These hypnozoites are not killed by chloroquine or quinine. A. Most vivax malaria worldwide is susceptible to chloroquine, but if vivax is treated without also giving primaquine to destroy the liver stages of the parasite (effect a "radical cure"), it will relapse about three weeks later. B. The correct answer. C. Quinine will treat vivax malaria, but is poorly tolerated (it is bitter, may cause hypoglycaemia, vomiting and tinnitus). It is therefore not used unless alternatives are not available. Quinine does not kill hypnozoites and wthe malaria may relapse. D. Co-artem is effective against vivax malaria, but is not known to kill hypnozoites. E. In the past, quinine treatment for falciparum was often "finished" with doxycycline, because long courses of quinine are often poorly tolerated. However, neither quinine nor doxycycline are effective against hypnozoites.
• 86
  What haematological investigation must always be performed prior to starting primaquine therapy?
  Difficulty: Medium     Topic: Tropical diseases
  a

  Direct Coombs' test

  b

  Haemoglobin electrophoresis

  c

  Sickle cell screen

  d

  G6PD activity

  e

  Erythrocyte sedimentation rate
  Explanation: Primaquine will induce haemolysis in patients with G6PD deficiency. The pentose-phosphate pathway is the only source of reduced glutathione in erythrocytes. In G6PD-deficiency, the erythrocytes cannot replenish reduced glutathione under conditions of oxidative stress and haemolysis occurs. It is critical therefore to test for G6PD deficiency prior to starting a patient on primaquine. In patients with G6PD deficiency. In patients with G6PD deficieny, specialist advice from a tropical medicine unit should be sought. An intermittent eight-week regimen may be recommended. A. The direct Coombs' test is useful when screening for autoimmune causes of haemolytic anaemia. B. Haemoglobin electrophoresis is useful in the diagnosis of haemoglobinopathy, not enzyme deficiency. C. The sickle screen is a screening test for sickle cell anaemia. D. The correct answer. E. ESR is a general measure of inflammation due to inflection and autoimmune disease.
• 87
  You are a junior doctor in accident and emergency. An 18-year-old medical student presents with a two-day history of fever and nausea, for which he has been taking paracetamol with no effect. He returned five days ago from a three-month elective to Malawi, during which he reports multiple trips to go scube diving in Lake Malawi. The diving instructor assured him that there was no bilharzia in that part of Lake Malawi. He is normally fit and well. On examination, he has a fever of 38.3°C, with widespread lymphadenopathy and slight hepatosplenomegaly. An urgent blood film does not show any malaria parasites, but does show an eosinophilia. What is the diagnosis?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Black water fever

  b

  Katayama fever

  c

  Malaria

  d

  Allergic reaction

  e

  Glandular fever
  Explanation: The history of swimming in Lake Malawi suggests the diagnosis of acute schistosomiasis (Katayama fever). Lake Malawi is endemic for bilharzia (Schistosoma infection) which is caused by a fluke that burrows through the skin of the swimmer and sets up residence in the splanchnic veins. Information usually provided by tourist agents in Malawi is that parts of Lake Malawi are bilharzia-free and safe to swim in: this is never true. Treatment is praziquantel. A. Black water fever occurs when haemoglobinuriea occurs in severe malaria. B. The correct answer. C. Malaria does not normally cause an eosinophilia. D. Any drug allergy can cause eosinophilia, but drug allergy does not explain the fever. E. Glandular fever does not usually cause eosinophilia.
• 88
  A 48-year-old man presents to his GP with sudden onset irritation in his eye and a sensation that there is foreign body there. He was born in Nigeria, but has been in the UK for six years now. On examination, there is a thin transparent worm present in the subconjunctiva of his eye. What is the diagnosis?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Schistosoma mansoni

  b

  Hookworm

  c

  Loa loa

  d

  Onchocerca volvulus

  e

  Dermatobia hominis
  Explanation: The clinical findings are pathognomic for African eye worm (Loa loa infection). The worm can usually be paralysed with cocaine and removed surgically. Loa loa is transmitted by the bite of the deer fly (genus Chrysops) and is endemic to West Africa. The worms migrate subcutaneously (Calabar swellings) and normally cause few symptoms unless they pass under the conjunctiva. Treatment with diethylcarbamazine is effective but should only be given under specialist supervision because of the risk of fatal encephalitis. A. The parasites of Schistosomiasis are in the splanchnic veins. B. Hookworm is usually present in the gut. C. The correct answer. D. O. volvulus is a cause of river blindness in West Africa. It is a cause of filariasis and river blindness, but only mirofilariae travel across the conjunctivae and are not visible to the naked eye. E. The larva of D. hominis is large with circumferential rings of spikes.
• 89
  A 28-year-old soldier returned four weeks ago from a training exercise in Peru. He has a single boil on his head that is growing larger despite oral flucloxacillin prescribed by his unit medical officer. He is normally fit and well. On examination, there is a single nodule about 2 cm in diameter with a central pore. You cover the punctum with clear gel and are able to see an air bubble develop. What is the diagnosis?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Schistosoma mansoni

  b

  Hookworm

  c

  Loa loa

  d

  Onchocerca volvulus

  e

  Dermatobia hominis
  Explanation: The clinical picture is typical of Dermatobia hominis, a botfly that lays its eggs on mosquitoes. The eggs hatch when the mosquito bites its victim, and the maggot quickly burrows into the skin, where it forms a cavity and slowly grows to maturity over 5-10 weeks. Treatment is paralysis of the botfly with lidocaine followed by surgical removal. A. The adult flukes of Schistosoma are present in the splanchnic veins. B. hookworms are normally present in the gut. C. The adult worms of Loa loa are present subcutaneously as Calabar swellings or visible subconjunctivally. D. The adult worms of O. volvulus are normally present as subcutaneous nodules but do not have a central pore and are not endemic to Peru. E. The correct diagnosis.
• 90
  You are a junior doctor in the accident and emergency department. A 34-year-old woman attends the department complaining of blood in her eyes and urine. She returned from rural Nigeria three days ago, where she was visiting family. On examination, she has a fever of 39.5°C, and is actively bleeding from her eyes and gums. What should you do next?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Take an urgent blood sample for clotting.

  b

  Urgently crossmatch 4 units of blood.

  c

  Confirm haematuria by dipstick examination of urine.

  d

  Take an urgent blood film for malarial parasites.

  e

  Isolate the patient in a side room and refer urgently to infectious diseases.
  Explanation: This woman has viral haemorrhagic fever until proven otherwise. Causes of viral haemorrhagic fever (VHF) from West Africa include Ebola, Lassa and Marburg virus. All bodily fluids (urine, tears, blood) are contagious. The patient should be isolated immediately and no blood samples should be taken for any reason except with full contact precautions and under supervision of a specialist in infectious diseases or virology. No specific treatment is available for most causes of VHF and mortality is up to 90%. No vaccine is available. There are two isolation facilities for viral haemorrhagic fever in the UK, one in London and the second in Newcastle. A–D. No blood samples or samples of any bodily fluid should be collected for any reason whatsoever from a patient with suspected viral haemorrhagic fever. E. The correct answer.
• 91
  You are a junior doctor in an acute medical unit in the UK. A 23-year-old medical student presents with a two-day history of fever and myalgia. He has just returned from a three-month elective in Thailand. On examination, he is febrile, 38.5°C and his gums are bleeding. The remainder of the clinical examination is normal. On his left arm are a flush of petechiae above the elbow: he says this only came on after the nurse took his blood pressure in that arm. His packed cell volume (haematocrit) is 0.64 and his platelet count is 20. A malaria film is negative. What is the diagnosis?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Dengue

  b

  Malaria

  c

  Yellow fever

  d

  Leukaemia

  e

  Meningococcal septicaemia
  Explanation: The most likely diagnosis is dengue. The WHO no longer divide dengue into haemorrhagic and non-haemorrhagic: instead the division severe and non-severe is used. Features of severe dengue are: shock, pulmonary oedema, severe bleeding, ALT ≥1000, impaired consciousness or other end organ impairment. The WHO recommends the tourniquet test as a simple bedside diagnostic test for dengue: the test is no longer used as part of the criteria for haemorrhagic fever. To perform the test, apply a blood pressure cuff to the arm and inflate to midway between systolic and diastolic blood pressure for five minutes. Twenty or more petechiae within a one inch square indicates a positive result. The test looks for increased capillary fragility that occurs in dengue. This patient has had an unintentional tourniquet test and it will have to be repeated on the contralateral arm to be interpretable. Increased vacuscular permeability causes loss of circulating plasma, which in turn results in a rise in packed cell volume (also known as haematocrit). Dengue is the most common cause of viral haemorrhagic fever (VHF) worldwide and like other causes of VH, treatment is largely supportive (intravenous rehydration only). A. The correct answer. B. Malaria would explain the fever and the thrombocytopaenia, but the malaria film is negative and malaria does not explain the elevated packed cell volume. However, malaria does occur in Thailand and is therefore a valid differential. C. Yellow fever is not endemic to Thailand, but is endemic to Africa and South America. D. Leukaemia can produce all of the clinical features, including fever, high haematocrit and bleeding tendency. It is therefore a valid differential, however, the recent travel to Thailand suggests an alternative diagnosis. E. Spontaneously produced petechiae would be more suggestive of meningococcal septicaemia, rather than a localised flush of petechiae that appear only after application of a tourniquet. Also, the history of travel to Thailand suggests an alternative diagnosis.
• 92
  You are a junior doctor in an acute medical unit in the UK. A 23-year-old medical student presents with a two-day history of fever. He has returned three weeks ago from a three-month elective in Thailand. What disease does not appear in the differential diagnosis?
  Difficulty: Hard     Topic: Tropical diseases
  a

  Dengue

  b

  Malaria

  c

  Melioidosis

  d

  Hepatitis A

  e

  Typhoid
  Explanation: This is a question about the importance of knowing incubation periods. This allows the clinician to eliminate diseases from the differential that are otherwise clinically indistinguishable. A. The correct answer. Dengue has an incubation period of 3–14 days. The patient is therefore outside the incubation period for dengue. Also excluded from the differential are other arboviruses such as Chikungunya (2–12 days), Japanese encephalitis (5–15 days) and Rickettsial diseases such as scrub typhus (5–14 days). B. Malaria should be suspected up to a year after returning from a malaria-endemic area, although most cases occur within the first three months. C. Melioidosis (Burkholderia pseudomallei infection) can present many decades after initial exposure: the longest recorded is 62 years. D. Hepatitis A has an incubation period of 15–50 days. E. Typhoid has an incubation period of 3–60 days (though usually 8-14 days).
• 93
  You are a junior doctor in an accident and emergency department. A 53-year-old man presents with a three-day history of fever and headache. He is normally fit and well. On examination, he has a fever of 39.3°C, with photophobia and neck stiffness. A lumbar puncture is performed and microscopic examination of cerebrospinal fluid shows polymorphs and Gram-positive cocci. What is the causative organism?
  Difficulty: Easy     Topic: Emergencies
  a

  Capnocytophaga canimorsus

  b

  Neisseria meningitidis

  c

  Haemophilus influenzae

  d

  Streptococcus pneumoniae

  e

  Escherichia coli
  Explanation: A. C. canimorsus is a Gram-negative coccobacillus that is associated with dog bites. B. Neisseria meningitidis is a Gram-negative diplococcus. C.H. influenzae is a Gram-negative bacillus. D. The correct answer. E. E. coli is a Gram-negative bacillus (rod) that causes neonatal meningitis.
• 94
  You are a junior doctor in an accident and emergency department. A 19-year-old man presents with a three-day history of fever and headache. He is normally fit and well. On examination, he has a fever of 39.3°C, with photophobia and neck stiffness. A lumbar puncture is performed and microscopic examination of cerebrospinal fluid shows polymorphs and intracellular Gram-negative diplococci. What is the causative organism?
  Difficulty: Easy     Topic: Emergencies
  a

  Capnocytophaga canimorsus

  b

  Neisseria meningitidis

  c

  Haemophilus influenzae

  d

  Streptococcus pneumoniae

  e

  Escherichia coli
  Explanation: A. C. canimorsus is a Gram-negative coccobacillus that is associated with dog bites. B. The correct answer. Neisseria meningitidis is a Gram-negative diplococcus (the cocci appear as pairs on microscopy). C.H. influenzae is a Gram-negative bacillus. D. S. pneumoniae is a Gram-positive coccus. It is, however, easily decolourised on Gram stain which allows it to sometimes be mistaken for N. meningitidis. E. E. coli is a Gram-negative bacillus that causes neonatal meningitis.
• 95
  You are a junior doctor in an accident and emergency department. A 53-year-old man presents with a five-day history of fever and headache. He was bitten by his pet dog nine days previously. He drinks 50 units of alcohol per week, but is normally fit and well. On examination, he has a fever of 39.3°C, with photophobia and neck stiffness. A lumbar puncture is performed and microscopic examination of cerebrospinal fluid shows polymorphs and Gram-negative rods. What is the causative organism?
  Difficulty: Hard     Topic: Emergencies
  a

  Capnocytophaga canimorsus

  b

  Neisseria meningitidis

  c

  Haemophilus influenzae

  d

  Streptococcus pneumoniae

  e

  Escherichia coli
  Explanation: A. Capnocytophaga canimorsus is a rare cause of meningitis in humans. C. canimorsus is a normal commensal of the canine oral cavity and was probably transmitted to this patient by dog bite. Risk factors include asplenism, alcohol abuse (as in this case) and cardiac failure. CSF examination shows Gram-negative rods in ~75% of cases. The organism is susceptible to penicillin, cephalosporins, carbapenems tetracyclines and quinolones. B. Neisseria meningitidis is a Gram-negative diplococcus. C. Haemophilus influenzae is a Gram-negative coccobacillus. It normally occurs in unvaccinated children. D. Streptococcus pneumoniae is a Gram-positive coccus. E. Escherichia coli is a Gram-negative bacillus that causes neonatal meningitis.
• 96
  You are the junior doctor on-call for paediatric admissions at a district general hospital. A mother brings in a two-day-old baby with fever and listlessness. There is no evidence of meningism but the child is drowsy and not feeding. Breathing is rapid and shallow. There is no visible rash. Combined chest and abdominal radiograph is normal. An emergency lumbar puncture demonstrates Gram-negative bacilli on CSF microscopy. What is the causative organism?
  Difficulty: Easy     Topic: Emergencies
  a

  Listeria monocytogenes

  b

  Neisseria meningitidis

  c

  Haemophilus influenzae

  d

  Streptococcus agalactiae

  e

  Escherichia coli
  Explanation: The child has E. coli meningitis. A. Listeria is a Gram-positive bacillus. It is responsible for 7% of all cases of neonatal meningitis presenting in the first week of life. B. N. meningitidis a Gram-negative diplococcus. C. H. influenzae is a Gram-negative bacillus that causes meningitis in infants, but not usually in the first week of life. D. S. pneumoniae is responsible for 39–48% of all cases of neonatal meningitis in the first week of life. It is a Gram-positive coccus. E. The correct answer. E. coli is responsible for 18–26% of all cases of neonatal meningitis presenting within the first week of life. It is a Gram-negative bacillus.
• 97
  You are the junior doctor on-call for paediatric admissions at a district general hospital. A mother brings in a two-day-old baby with fever and listlessness. There is no evidence of meningism but the child is drowsy and not feeding. Breathing is rapid and shallow. There is no visible rash. Combined chest and abdominal radiograph is normal. An emergency lumbar puncture demonstrates Gram-positive cocci on CSF microscopy. What is the causative organism?
  Difficulty: Easy     Topic: Emergencies
  a

  Listeria monocytogenes

  b

  Neisseria meningitidis

  c

  Haemophilus influenzae

  d

  Streptococcus agalactiae

  e

  Escherichia coli
  Explanation: The child has Streptococcal neonatal meningitis. The most likely cause is group B streptococcus (S. agalactiae), which causes 39–48% of cases of neonatal meningitis presenting in the first week of life, but Streptococcus pneumoniae is also possible (6% of cases). A. Listeria is a Gram-positive bacillus. It is responsible for 7% of all cases of neonatal meningitis presenting in the first week of life. B. N. meningitidis a Gram-negative diplococcus. C. H. influenzae is a Gram-negative bacillus that causes meningitis in infants, but not usually in the first week of life. D. The correct answer. E. E. coli is a Gram-negative bacillus. It is responsible for 18–26% of all cases of neonatal meningitis presenting within the first week of life.
• 98
  You are a junior doctor in accident and emergency. You have been called to see a 3-year-old female child who is generally unwell. On examination, she is listless and drowsy, with a fever of 38°6C. She is not photophobic and there is no nuchal rigidity. You count two new flat, non-blanching brownish-black spots on the right foot that her mother says were not there before. What do you do next?
  Difficulty: Easy     Topic: Emergencies
  a

  Review again in four to six hours. A minimum of five spots a needed to make the diagnosis of a purpuric rash.

  b

  Call for the on-call paediatrician to perform a lumbar puncture. Initiate treatment immediately after appropriate investigation.

  c

  Give intravenous ceftriaxone immediately.

  d

  Explain to the child's mother that she most likely has a viral exanthem. Discharge and ask GP to review in 24 hours.

  e

  Reassure mother and discharge. Prescribe ibuprofen and oral rehydration salts. Return to accident and emergency if child deteriorates.
  Explanation: The NICE guidelines recommend treatment as soon as invasive meningococcal disease (Neisseria meningitidis infection) is suspected. Meningococcal septicaemia can occur without meningitis, when carries a much worse prognosis than meningitis alone. A. There is no minimum number of spots needed to diagnose a purpuric rash. B. Treatment should not be delayed pending investigation. The progression of meningococcal septicaemia is minutes, not hours. Furthermore, in meningococcal septicaemia, positive cultures are most likely to be obtained from blood cultures, not lumbar puncture. C. The correct answer. Either penicillin or ceftriaxone should be given immediately and should not be delayed pending further investigation or hospital transfer. If intravenous access cannot be gained, then antibiotics should be given intraosseously. D. The child probably has meningococcal septicaemia, which is a life-threatening illness. E. The child requires urgent antibiotic thereapy and cannot be treated conservatively with watchful waiting.
• 99
  You are a junior doctor in accident and emergency. You have been called to see a 3-year-old female child who is generally unwell. On examination, she is listless and drowsy, with a fever of 38°6C. She is not photophobic and there is no nuchal rigidity. You count two new flat, non-blanching brownish-black spots on the right foot that her mother says were not there before. The mother tells you that the child had a rash with oral amoxicillin six months ago. What do you do next?
  Difficulty: Medium     Topic: Emergencies
  a

  Review again in four to six hours. A minimum of five spots a needed to make the diagnosis of a purpuric rash and you do not want to risk a serious allergic reaction with penicillin.

  b

  Call for the on-call paediatrician to perform a lumbar puncture. Initiate treatment immediately after appropriate investigation.

  c

  Give intramuscular penicillin immediately.

  d

  Explain to the child's mother that she most likely has a viral exanthem. Review again in 24 hours.

  e

  Give intravenous chloramphenicol immediately.
  Explanation: This child has meningococcal septicaemia. The NICE guidelines recommend treatment as soon as invasive meningococcal disease (Neisseria meningitidis infection) is suspected. Meningococcal septicaemia can occur without meningitis, when it carries a much worse prognosis than meningitis alone. A. There is no minimum number of spots needed to diagnose a purpuric rash. B. Treatment should not be delayed pending investigation. The progression of meningococcal septicaemia is minutes, not hours. Furthermore, in meningococcal septicaemia, positive cultures are most likely to be obtained from blood cultures, not lumbar puncture. C. The correct answer. Either penicillin or ceftriaxone should be given immediately and should not be delayed pending further investigation or hospital transfer. If intravenous access cannot be gained, then antibiotics should be given intraosseously. D. The child probably has meningococcal septicaemia, which is a life-threatening illness. E. The child requires urgent antibiotic thereapy and cannot be treated conservatively with watchful waiting.
• 100
  You are a junior doctor in accident and emergency. You have been called to see a 3-year-old female child who is generally unwell. On examination, she is listless and drowsy, with a fever of 38°6C. She is not photophobic and there is no nuchal rigidity. You count two new flat, non-blanching brownish-black spots on the right foot that her mother says were not there before. The mother tells you that the child had an anaphylactic reaction with oral amoxicillin six months ago. What do you do next?
  Difficulty: Hard     Topic: Emergencies
  a

  Review again in four to six hours. A minimum of five spots a needed to make the diagnosis of a purpuric rash and you do not want to risk a serious allergic reaction with penicillin.

  b

  Call for the on-call paediatrician to perform a lumbar puncture. Initiate treatment immediately after appropriate investigation.

  c

  Give intramuscular penicillin immediately.

  d

  Explain to the child's mother that she most likely has a viral exanthem. Review again in 24 hours.

  e

  Give intravenous chloramphenicol immediately.
  Explanation: The NICE guidelines recommend treatment as soon as invasive meningococcal disease (Neisseria meningitidis infection) is suspected. Meningococcal septicaemia can occur without meningitis, when carries a much worse prognosis. Penicillin should be given even if there is a history of a rash, but it should be withheld if there is a history of anaphylaxis. A. There is no minimum number of spots needed to diagnose a purpuric rash. B. Treatment should not be delayed pending investigation. The progression of meningococcal septicaemia is minutes, not hours. Furthermore, in meningococcal septicaemia, positive cultures are most likely to be obtained from blood cultures, not lumbar puncture. C. The correct answer. Either penicillin or ceftriaxone should be given immediately and should not be delayed pending further investigation. A history of rash is not a contraindication to penicillin for suspected invasive meningococcal disease, but a history of anaphylaxis is a contra-indication. D. The child probably has meningococcal septicaemia, which is a life-threatening illness. E. The NICE guidelines do not make any recommendation what to do in the event of a history of serious allergy to penicillin. There is long historical experience of chloramphenicol in meningitis, but chloramphenicol is no longer used first-line because it is associated with bone marrow suppression and (very rarely) aplastic anaemia. However, given the history of anaphylaxis to penicillin, cephalosporins (possibly carbapenems) are contraindicated as well. In the abscence of other alternatives, chloramphenicol is a good alternative.
• 101
  A 57-year-old man presents to accident and emergency with a two-day history of a painful left leg. There is no history of trauma to that leg. He has diabetes, but is otherwise fit and well. On examination, he is screaming with pain, despite having received 10 mg of morphine intravenously. On examination, he is febrile 39.5°C, tachycardic 126 beats/min, but his blood pressure is stable. His leg is mildly erythematous and swollen, but extremely painful and exquisitely tender to touch. He is unable to weight-bear on that leg. What is the diagnostic investigation?
  Difficulty: Medium     Topic: Emergencies
  a

  Refer for urgent surgical exploration and possible debridement.

  b

  Perform an urgent X-ray to look for a pathological fracture.

  c

  Perform an urgent X-ray to look for subcutaneous gas.

  d

  Perform an urgent ultrasound to look for a deep vein thrombosis.

  e

  Perform an urgent ultrasound to look for subcutaneous gas.
  Explanation: The combination of extreme pain with few clinical signs in a man with diabetes must raise the suspicious of necrotising fasciitis. The classic textbook picture of haemorrhagic bullae, crepitus and skin necrosis develop late and therefore cannot be relied on to. Risk factors include diabetes mellitus (two thirds of all patients with necrotising fasciitis have diabetes), chronic hepatitis, malignancy and intravenous drug use. Varicella is a risk factor in children. 25% of cases present without any comorbidity or history of trauma. The diagnosis is made by surgical exploration, to look for necrotic fat and subcutaneous tissues. Imaging can be useful but generally only serves to delay. The microbiology of necrotising fasciitis is complex. Type 1 is polymicrobial with a mixture of Gram-positives Streptococci and Staphylococci), Gram-negatives (including Enterobacteraciae) and anaerobes (Clostrium species, but also Bacteroides, Prevotella and Peptostreptococcus) synergistically causing the rapid tissue destruction. Type 2 is monomicrobial and is caused by Streptococcus pyogenes. Initial antibiotic therapy should be broad (advice from microbiology or infectious diseases should be sought) and the regimen will usually include an antibiotic that inhibits toxin synthesis (e.g., clindamycin). A. The correct answer. B, C. X-rays may demonstrate subcutaneous gas or gas within the muscles produced by gas-forming anaerobes, however, this is an unnecessary investigation since the diagnosis is obtained surgically. It is incorrect to delay potentially life-saving surgery to obtain imaging that only confirms the need for surgery. D, E. Ultrasound may reveal gas in the subcutaneous tissues which is suggestive of necrotising fasciitis. However, the clinical picture is that of necrotising fasciitis and what the patient needs immediately is surgery, not imaging, which will only delay the surgery.
• 102
  A 5-year-old girl presents to accident and emergency with a six-day history of fever, lethargy, cough and multlple vesicles. She was a normal term-delivery and is normally fit and well, with her weight on the 80th percentile. All her childhood vaccinations were up-to-date (varicella immunisation is not offered in the UK). On examination, she is in obvious pain. She is febrile, tachypnoeic and tachycardic. There are a mixture of new and old elliptical vesicles predominantly over her face, chest, and abdomen, but also affecting her limbs. The skin over her abdomen and right leg seems faintly dark and mottled, and the pain localises here. What do you do next?
  Difficulty: Hard     Topic: Emergencies
  a

  A full blood count, biochemistry and C-reactive protein are needed urgently to assess severity.

  b

  Break a a vescle with a sterile needle and take an urgent Tzanck smear for urgent bedside microscopy.

  c

  Start intravenous aciclovir.

  d

  Re-assure father that the child has chicken pox and that she may be generally unwell for 10 to 14 days in total.

  e

  Refer for urgent surgical exploration and possible debridement.
  Explanation: The child has necrotising fasciitis, which is a rare complication of chicken pox in young children. The fever, cough and elliptical vescicles with a centripetal distribution. She needs urgent surgical exploration and debridement, together with penicillin-based antibiotic therapy. The necrotizing fasciitis associated with chicken pox is usually due to Streptococcus pyogenes and the antibiotic regiment should therefore be penicillin-based. A. It is clear from the clinical picture alone that the child is severely unwell. A FBC, U&E and CRP will be useful, but are not the first priority. B. A Tzanck smear is an obsolete test to look for herpes virus infection. A glass smear of an ulcer base stained with Giemsa will show multinucleate giant cells. This has been superceded in most hospitals by PCR for varicella zoster virus. In this instance, the clinical picture is typical of chicken pox and a laboratory diagnosis is probably unnecessary. C, D. The child indeed has chicken pox, for which aciclovir is the correct therapy. However, the extreme pain, mottled skin and clinical signs of sepsis, all suggest that there is something else going on as well. D. The correct answer.
• 103
  You are a GP. A 28-year-old male saw your colleague 5 days ago with pain and stinging on passing urine, for which she prescribed a three-day course of trimethoprim. The patient has returned today because he is no better. The midstream urine (MSU) from his previous visit has grown nothing. What should you do next?
  Difficulty: Medium     Topic: Sexual health
  a

  Prescribe a two-week course of trimethoprim.

  b

  Prescribe a five-day course of amoxicillin.

  c

  Give a single dose of ciprofloxacin.

  d

  Prescribe a two-week course of doxycycline.

  e

  Refer urgently for a full sexual health screen.
  Explanation: Urinary tract infections are rare in young men. The most common cause of dysuria in a young man is urethritis, and the most common causes of urethritis are sexually transmitted (Neisseria gonorhoeae and Chlamydia trachomatis). A urethral swab and Gram stain can quickly determine whether the cause is gonococcal, but few GPs in the UK have facilities to do this. Sexually transmitted diseases hunt in packs, so a sexual health clinic will also check for HIV, syphilis and other infections at the same time. A. The patient has urethritis and not a UTI. Trimethoprim is inappropriate. B. Most causes of a urethritis are resistant to amoxicillin. C. Ciprofloxacin used to be the treatment of choice for gonococcal urethritis, but you do not yet know the causative organism let alone the susceptibility profile. D. Doxycycline will reliably treat Chlamydia infection, but you do not yet know the causative organism. E. The correct answer.
• 104
  You are a junior doctor in a sexual health clinic. A 22-year old man presents with urethral discharge and pain on passing urine. There are threads of pus in the first-pass urine and microscopic examination of a urethral swab shows intracellular Gram-negative diplococci. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Sexual health
  a

  Chlamydia trachomatis urethritis

  b

  Neisseria gonorrhoea (gonococcal) urethritis

  c

  Escherichia coli cystitis

  d

  Primary syphilis

  e

  Human papillomavirus (HPV) infection
  Explanation: Intracellular Gram-negative diplococci are almost pathognomic of Neisseria gonorrhoeae infection.The only other differential is meningococcal urethritis, which is rare. A. Chlamydia is diagnosed on cell culture or PCR. B. The correct answer. C. E. coli cystitis does not cause a penile discharge. D. Primary syphilis normally causes a chancre, not a discharge. E. HPV normally causes warts.
• 105
  You are a junior doctor in a sexual health clinic. A 35-year-old man presents for a routine sexual health screen. He is sexually active with multiple female partners and has been attending regularly for years. He has a new ulcer on his glans penis, which is painless and indurated. Dark field microscopy of the ulcer swab shows delicate, corkscrew-shaped organisms. What is the most likely diagnosis?
  Difficulty: Easy     Topic: Sexual health
  a

  Primary syphilis

  b

  Latent syphilis

  c

  Herpes simplex type 2

  d

  Secondary syphilis

  e

  Systemic lupus erythematosus (SLE)
  Explanation: The demonstration of treponemes (delicate, corkscrew-shaped organisms) on darkfield microscopy from a genitcal ulcer swab is almost certainly syphilis. There is a differential (bejel, pinta and yaws may all produce similar appearances), but given the sexual history, syphilis is the only plausible diagnosis. A. The correct answer. B. This cannot be latent syphilis because he is symptomatic. C. The ulcers of herpes simplex are painful, not painless, and ought not to have treponemes in them. D. Secondary syphilis presents with malaise, rash and lymphadenopathy. E. SLE may cause skin lesions anywhere on the body, but these are usually painful and ought not to have treponemes in them.
• 106
  You are a junior doctors in a sexual health clinic in the UK. You diagnosed asymptomatic HIV in a 28-year-old man one month ago. You asked him to inform his regular sexual partner of his diagnosis of HIV so that his partner can be screened. He had not done so by his two week appointment and you gave him a further two week deadline to do so. He has returned to clinic today (a month later) to discuss his blood results, but you discover that he has still not asked his partner to attend for HIV screening. What is the most appropriate course of action?
  Difficulty: Easy     Topic: Sexual health
  a

  You have discharged your duty of care to your patient and cannot take matters any further.

  b

  Inform the partner yourself.

  c

  Set another deadline for your patient to inform his partner.

  d

  Ask the police to inform the partner.

  e

  Refer the matter to the police, asking your patient to be charged with grevious bodily harm.
  Explanation: This is one of the few circumstances under which you are obliged to breach your duty of confidentiality to your patient. The UK General Medical Council guidance on Confidentiality (2009) states that "Disclosure of personal information about a patient without consent may be justified in the public interest if failure to disclose may expose others to a risk of death or serious harm." The situation in the US is much less clear: the AMA advise that "If there is a reasonable probability that a patient will inflict serious bodily harm on another person, for example, the physician should take precautions to protect the intended victim..." However, it is very unclear whether this principle extends to HIV, and remains a subject for debate. A. You have not discharged your duty to the public good. B.The correct answer. C. You have already set a deadline that has passed. D. It is the duty of the doctor to inform the partner and this duty cannot be delegated to the police. E. A person with HIV who deliberately transmits HIV to another may indeed be charged with GBH, but you have no evidence that this has happened.
• 107
  You are a GP. A 22-year-old woman attends your clinic with a two-week history of vulval itch and soreness. On examination, the vulva are red and fissured, with a curdy discharge. What is the most appropriate course of action?
  Difficulty: Easy     Topic: Sexual health
  a

  Prescribe a 14-day course of doxycycline.

  b

  Prescribe a single dose of IM ceftriaxone.

  c

  Perform a speculum examination for cervicitis.

  d

  Prescribe a single dose of fluconazole.

  e

  Reassurance only.
  Explanation: These are typical symptoms and signs of vulvovaginal candidiasis. The most common organism causing this is Candida albicans. Take a sample for fungal culture (Sabouraud's medium), because fluconazole resistance is common. Fluconazole is a reasonable choice for empirical therapy. Other alternatives include topical clotrimazole, nystatin and miconazole. A. Doxycycline is used empirically to treat Chlamydia, not Candida. B. IM ceftriaxone is the current first-line treatment for gonorrhoea. C. A speculum examination is not part of the management of vulval candidiasis, but may be sometimes be indicated as part of a screen for sexually transmitted diseases. D. The correct answer. A sample should be taken for fungal culture. E. Asymptomatic colonisation with Candida occurs in 10–20% of women of reproductive age, and does not require treatment. However, this woman is symptomatic and should be treated.
• 108
  Malaria is transmitted by mosquitoes of which genus?
  Difficulty: Easy     Topic: Parasitology
  a

  Aedes

  b

  Anopheles

  c

  Culex

  d

  Haemagogus

  e

  Mansonia
  Explanation: A. Aedes mosquitoes transmit dengue and yellow fever in Africa and Asia. B. The correct answer. C. Culex transmits West Nile virus and Japanese encephalitis. D. Haemagogus mosquitoes are an important vector for yellow fever in South America. E. Mansonia mosquitoes transmit Brugia malayi (lymphatic filariasis).
• 109
  You are a GP in the UK. A 42-year-old man has just returned from a business trip to New York. He thinks he has picked up some kind of parasite because he is itching all over. He is normally fit and well. He shows you three eythematous papules in a line (each about a centimetre apart) on his arm as proof, but is unable to describe the parasite that bit him. He has burnt all his clothes and is about to call in a pest controller. What is the diagnosis?
  Difficulty: Hard     Topic: Parasitology
  a

  Ticks

  b

  Mosquitoes

  c

  Spiders

  d

  Bedbugs

  e

  Wasps
  Explanation: The bedbug (Cimex lectularius) is a small brown dorsoventrally flattened insect that feeds on humans and domestic animals. It is about the size of an appleseed. The insect has six stages and each stage requires a blood meal to progress to the next stage. When a host is available, the insect will feed every 3-7 days, but in cold environments, they can survive for as long as two years without feeding. The insects hide behind peeling wallpaper or plaster, or cracks in furniture. They usually come out only at night to feed: to see a bedbug during the day means the infestation is very heavy. Bedbugs are not known to be vectors of disease. The bite itself is anaesthetic and it may take as long as 11 days following a bite before the victim realises he has been bitten, which means that when levels of infestation are low, the victim may never see the insect or realise when the bites are happening. The bites characteristically occur three or four in a line ("breakfast-lunch-and-dinner" arrangement) as occured in this patient. New York has had an epidemic that started around 2002, and the bugs may be carried on clothes, luggage or furniture. Professional pest control is usually required: bedclothes must be washed at 60°C and furniture may need to be dismantled to identify hidning places. A. Tick bites are generally painless and the victim may not realise he has been bitten, although the ticks are readily visible. The bites are seldom multiple and are usually associated wtih walking outdoors. B. Mosquito bites are usually itchy immediately afterwards and victims are usually aware of the insects from the sound they make. C. Most spiders in the UK do not bite. D. The correct answer. E. Wasps stings are immediately painful and the victim is almost always aware of the bite when it happens.