mcem microbiology mcq

MCEM Microbiology MCQ

1. Orbital cellulitis:(a) The infection has not breached the orbital septum True FalseIf the infection has not breached the orbital septum it is a pre-septal ( or periorbital ) cellulitis (b) Streptococcus is the most common pathogen. True FalseStaphylcoccus Aureus is the most common pathogen. .(c) Klebsiella is a common pathogen in young children True FalseHaemophilus is a common pathogen in young children(d) Polymicrobial infection is common. True FalsePolymicrobial infection is common. (e) Extension from conjunctivitis is the most common source. True FalseExtension from paranasal sinus infection is the most common source.

2. Streptococci: (a) Humans are the only host of S. pneumoniae and most carriage is asymptomatic True FalseHumans are the only host of S. pneumoniae and most carriage is asymptomatic (b) Children under 1 year of age are especially susceptible to acute pneumonia from S. pneumoniae. True FalseChildren under 1 year of age are especially susceptible to acute pneumonia from S. pneumoniae. (c) The produced toxin neuraminidase is the main pathogenicity determinant of S. pneumoniae. True FalseThe capsule is the main pathogenicity determinant of S. pneumoniae. (d) Otitis Externa, pharyngitis and acute pneumonia are the most common infections related to strep pneumonia

True False

Acute otitis media, sinusitis and acute pneumonia are the most common infections related to strep pneumonia (e) S. Pneumonia is generally sensitive to rifampicin True FalseS. Pneumonia is generally sensitive to rifampicin

3. The following are true with regard to gastroenteritis:(a) The incubation period for staphylococcus aureus is approximately 10-12 hours. True FalseThe incubation period for staphylococcus aureus is approximately 1-6 hours. (b) The incubation period for bacillus cereus is approximately 12-15 hours. True FalseThe incubation period for bacillus cereus is approximately 1-5 hours. (c) The incubation period for scrombotoxin is approximately 3-5 hours. True FalseThe incubation period for scrombotoxin is approximately 10-60 minutes.(d) The incubation period for salmonella is approximately 12-48 hours. True FalseThe incubation period for salmonella is approximately 12-48 hours.

4. Pyelonephritis: Appropriate Antibiotics:(a) Gentamicin True FalseGentamicine is renal and oto-toxic and blood levels should be monitored. (b) Ciprofloxacin. True FalseA quinolone which inhibits DNA gyrase. (c) Cefuroxime True FalseBut not early cephalosporins such as cephradine (d) Co-Amoxyclav True FalseAmpicillin and clavulinic acid. (e) Ampicillin True False40-50% of coliforms will be resistant to ampicillin and coliforms are a frequent cause of pyelonephritis

40-50% of coliforms will be resistant to ampicillin.

5. Otitis Externa:(a) If there is associated peforation of the tympanic membrane the topical antibiotic of choice is an aminoglycoside.

True False

Because of reports of ototoxicity topical aminoglycosides are contraindicated in cases of perforated eardrums. (b) An effective treatment is the insertion of ribbon gauze dressing soaked with aluminium acetate solution.

True False

Or the insertion of ribbon gauze soaked with corticosteroid ear drops.


(c) If a systemic anti-bacterial is required flucloxacillin is the drug of choice for anti-pseudomonal activity.

True False

Flucloxacillin is usually an appropriate anti-bacterial for cases of otitis externa but if anti-pseudomonal activity is required then ciproxin ( or an aminoglycoside ) is required.(d) Neomycin is indicated for long term prophylaxis. True FalseNeomycin may be used for a week or so as excessive use may result in skin infections. (e) Chloramphenicol is an appropriate choice for topical infections. True False10% of patients will not tolerate the vehicle in the chloramphenicol preparation ( propylene glycol ) due to hypersensitivity.

6. Acute Sinusitis Y:(a) Is not a cause of localised tenderness. True FalseAcute sinusitis is a cause of localised tenderness, fever and facial pain. (b) H. Influenza is not a common causative organism False True FalseH. Influenza is a common causative organism in acute sinusitis.(c) E. Coli is a common organism True FalseE. Coli is not a common causative organism of acute sinusitis. (d) Strep Pyogenes is not a frequent causative organism True FalseStrep Pyogenes is a frequent causative organism of acute sinusitis as is strep pneumonia and H. influenza. (e) Metronidazole is first line therapy. True FalseAmoxicillin is first line therapy for acute sinusitis.

7. The following associations are correct:(a) Yellow fever is transmitted to humans by the bite of a mosquito. True FalseYellow fever is transmitted to humans by the bite of a mosquito. (b) Rabies is a DNA virus True FalseRabies is an RNA rhabdovirus. (c) Infection by entry of larvae through skin- hookworm True FalseThe larval form's of some helminths can survive in soil or water. (d) Faecal-oral spread - shigellosis True FalseParticularly among children in residential institutions. (e) Hep A is spread by inocculation True FalseHep A is spread by ingestion of contaminated foods.

8. The common cold:(a) Rhinovirus is a rare causative organism. True FalseRhinovirus and Coronavirus are the 2 most common pathogens accounting for 50% of cases (b) Coronavirus is not a common pathogen True FalseRhinovirus and Coronavirus are the 2 most common pathogens accounting for 50% of cases (c) Infection with one serotype of rhinovirus does not confer immunity against other serotypes. True FalseThis is why the common cold is so common (d) Common colds are usually followed by lower respiratory tract infections True FalseCommon colds are not usually followed by lower respiratory tract infections (e) Common colds are less frequent in the first few years of life True FalseCommon colds are more frequent in the first few years of life.

9. Acute otitis media in children:(a) Streptococcus pneumonia is a common organism ( >40% of cases ) True FalseStreptococcus pneumonia is a common organism ( >40% of cases ) (b) Organisms that colonise the nasopharynx frequently cause acute otitis media. True FalseMicroorganisms enter the middle ear via the eustachian tube which is shorter and more horizontal in young children. (c) Haemophilus influenza may cause up to 40% of cases. True FalseHaemophilus influenza may cause up to 40% of cases. (d) Moraxella catarrhalis may cause acute otitis media in up to 15% of cases. True FalseMoraxella catarrhalis( 3rd commonest organism) may cause acute otitis media in up to 15% of cases.(e) Chlamydia pneumoniae may be a causative organism, particularly in children younger than 6 True False


months.Chlamydia pneumoniae may be a causative organism, particularly in children younger than 6 months.

10. Epididymo-orchitis: (a) Begins with sudden severe testicular pain. True FalseTesticular torsion begins with sudden severe testicular pain while the pain of epididymo-orchitis is typically more gradual in onset.(b) Is a complication of gonococcal urethritis and prostatitis. True FalseIs a complication of gonococcal urethritis and prostatitis(c) Is a manifestation of genital infection with ureaplasma spp True False

(d) Does not complicate the mumps virus. True FalseOrchitis may occasionally complicate the mumps virus.(e) Is not associated with tuberculosis. True FalseEpididymitis can be caused by mycobacterium tuberculosis.

11. Tetanus: (a) The exotoxin inhibits the release of GABA from presynaptic nerve terminals. True FalseThe exotoxin inhibits the release of GABA and glycine from presynaptic nerve terminals(b) Tetanus is associated with muscular laxity. True FalseTetanus is associated with muscular rigidity, violent muscular contractions and autonomic instability.(c) The incubation period is from 12 to 24 hours. True FalseThe incubation period is from 1 day to 1 month. (d) There is an association between puncture wounds and tetanus. True FalseThere is an association between puncture wounds and tetanus.(e) Minor abrasions cannot cause tetanus. True FalseMinor abrasions can cause tetanus.

12. Staph Aureus:(a) Staphylococcus Aureus is the most invasive species of staphylococcus and is differentiated from other species by possessing the enzyme coagulase

True False

Staphylococcus Aureus is the most invasive species of staphylococcus and is differentiated from other species by possessing the enzyme coagulase (b) Asymptomatic carriage of Staph Aureus is found in 40% of healthy people, in the skin, axilla or perineum

True False

Asymptomatic carriage of Staph Aureus is found in 40% of healthy people, in the skin, axilla or perineum (c) Catalase catalyses the conversion of fibrinogen to fibrin. True FalseCoagulase catalyses the conversion of fibrinogen to fibrin (d) Staph Aureus produces coagulase which breaks down host tissues. True FalseStaph Aureus produces extracellular lytic enzymes ( e.g lipase ) which break down host tissues(e) Staphylococcus pneumonia follows influenza, progresses rapidly, is cavitating and has a high mortality.

True False

Staphylococcus pneumonia follows influenza, progresses rapidly, is cavitating and has a high mortality

13. Emergency complications of malignancy(a) For neutorpaenic patients with bacteraemia the standard of therapy is commonly an aminoglycoside combined with an antipseudomonal b-lactam

True False

For neutorpaenic patients with bacteraemia the standard of therapy is commonly an aminoglycoside combined with an antipseudomonal b-lactam. (b) Common organisms for neutropaenic bacteraemia include E Coli True FalseGram negative bacilli including E Coli, Klebsiella, and pseudomonas are common. (c) Common organisms for neutropaenic bacteraemia include staph. epidermidis. True FalseGram positive cocci including staph epidermidis, staph aureus and strep viridans are common. (d) Common organisms for neutropaenic bacteraemia include strep. viridans True FalseGram positive cocci including staph epidermidis, staph aureus and strep viridans are common. (e) Vancomycin should be considered for severe mucositis with neutropaenic bacteraemia. True FalseVancomycin should be considered for severe mucositis with neutropaenic bacteraemia.


14. Otitis Externa:(a) Rarely relapses True FalseFrequently is chronic and relapsing. (b) Can occur in any age group True FalseAnd is characterised more by inflammation than infection ie a type of chronic dermatitis (c) Gram negative bacilli are rarely responsible. True FalseProteus and pseudomonas. Candida and aspergillus also isolated. (d) Aural toilet and topical antibiotics such as polymyxin are an appropriate approach to management True FalseAural toilet and topical antibiotics such as polymyxin are an appropriate approach to management (e) Pseudomonas infection in diabetics rarely requires treatment. True FalseAlmost always requires treatment and can progress to meningitis.

15. The following are true:(a) The incubation period for shigella is 2-3 days. True FalseThe incubation period for shigella is 2-3 days.(b) The incubation period for rotavirus is 1-4 weeks. True FalseThe incubation period for rotavirus is 1-7 days. (c) The incubation period for giardia lamblia is 2-4 days. True FalseThe incubation period for giardia lamblia is 1-4 weeks. (d) The incubation period for E Coli 12-72 hours True FalseThe incubation period for E Coli 12-72 hours

16. Cat Bites:(a) Have low infection rates if untreated True False50%(b) Have a high risk of developing tenosynovitis True FalseDue to long narrow teeth (c) Staphylococcus aureus is often associated with infection. True FalseStaphylococcus aureus is often associated with infection. (d) Pasteurella Multocida is often associated with infection. True FalsePasteurella Multocida is often associated with infection. (e) Anaerobes are not associated with cat bites True FalseAnaerobes are associated with cat bites.

Staphylococcus aureus ,Pasteurella Multocida , Streptococcus,Klebsiella,enterobacter and anaerobes are associated with cat bites

17. Antibiotics in clinical use: (a) Quinolones bind to the 50S ribosome interfering with protein synthesis. True FalseQuinolones inhibit bacterial DNA gyrase. Erythromycin binds to the 50S ribosome interfering with protein synthesis. (b) Fluoroquinolones are less active than quinolones against pseudomonas and Chlamydia. True FalseFluoroquinolones are more active than quinolones against pseudomonas and Chlamydia(c) Erythromycin is active against gram positive cocci, many anaerobes including bacteroides, mycoplasma and Chlamydia

True False

Erythromycin is active against gram positive cocci, many anaerobes not including bacteroides, mycoplasma and Chlamydia (d) Erythromycin does not cross the placenta True FalseErythromycin crosses the placenta(e) Erythromycin is excreted in the bile True FalseErythromycin is excreted in the bile

18. In necrotising fasciitis:(a) The most common sole organism is strep pyogenes True FalseThe infection may be mixed with aerobes and anaerobes or strep pyogenes may be the exclusive agent. (b) Infection is isolated to the epidermis and the dermis. True FalseInfection spreads along the deep fascial planes (c) Very rarely involves anaerobes. True FalseAnaerobes are commonly present in necrotising fasciitis.


(d) Blood cultures are usually positive True False

(e) Antibiotics alone are generally sufficient. True FalseEffective treatment depends on early surgical resection of infected tissue.

19. Septicaemia:(a) Mortality is approximately 10% True FalseAround 30% of patients die directly or indirectly from sepiticaemia. (b) White Cell count <2000 is associated with a better outcome True FalseLow WBC's are associated with worse outcomes. (c) Corticosteroids should almost always be started. True FalseThe role of corticosteroids is not clearly defined and they should not always be started. (d) Hypotension at initial presentation is associated with a worse outcome True FalseHypotension at initial presentation is associated with a worse outcome. (e) Single pathogen infections generally have better outcome's. True FalsePolymicrobial infections are associated with worse outcomes.

20. Haemophilus Influenza:(a) Is a small gram negative bacillus True FalseHaemophilus Influenza is a small gram negative bacillus. (b) Is a pathogen in humans only True FalseHuman pathogen only. (c) 50% of healthy people are carriers. True False50% of healthy people are carriers (d) 25% of people carry encapsulated strains True False5% of people carry encapsulated strains (e) Transmission is by direct contact or by inhalation of respiratory tract droplets. True FalseTransmission is by direct contact or by inhalation of respiratory tract droplets.

mcem microbiology mcq

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