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MCEM Microbiology MCQ 1. Orbital cellulitis: (a) The infection has not breached the orbital septum If the infection has not breached the orbital septum it is a pre-septal ( or periorbital ) cellulitis (b) Streptococcus is the most common pathogen. Staphylcoccus Aureus is the most common pathogen. . (c) Klebsiella is a common pathogen in young children Haemophilus is a common pathogen in young children (d) Polymicrobial infection is common. Polymicrobial infection is common. (e) Extension from conjunctivitis is the most common source.
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Extension 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 Tru e Humans are the only host of S. pneumoniae and most carriage is asymptomatic Tru (b) Children under 1 year of age are especially susceptible to acute pneumonia e from S. pneumoniae. Children under 1 year of age are especially susceptible to acute pneumonia from S. pneumoniae. Tru (c) The produced toxin neuraminidase is the main pathogenicity determinant of S. e pneumoniae. The capsule is the main pathogenicity determinant of S. pneumoniae. Tru (d) Otitis Externa, pharyngitis and acute pneumonia are the most common e infections related to strep pneumonia Acute otitis media, sinusitis sinusitis and acute pneumonia are the most common common infections related to strep pneumonia Tru (e) S. Pneumonia is generally sensitive to rifampicin e S. 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. The incubation period for staphylococcus aureus is approximately 1-6 hours. (b) The incubation period for bacillus cereus is approximately 12-15 hours. The incubation period for bacillus cereus is approximately 1-5 hours. (c) The incubation period for scrombotoxin is approximately 3-5 hours. The incubation period for scrombotoxin is approximately 10-60 minutes. (d) The incubation period for salmonella is approximately 12-48 hours.
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The incubation period for salmonella is approximately 12-48 hours. 4. Pyelonephritis: Appropriate Antibiotics: (a) Gentamicin Gentamicine is renal and oto-toxic and blood levels should be monitored. (b) Ciprofloxacin. A quinolone which inhibits DNA gyrase. gyrase. (c) Cefuroxime
MCEM Microbiology MCQ But not early cephalosporins such as cephradine (d) Co-Amoxyclav Ampicillin and clavulinic acid. (e) Ampicillin
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40-50% 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. 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. 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. 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. Neomycin 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. 10% 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. Acute sinusitis is a cause of localised tenderness, fever and facial pain. (b) H. Influenza is not a common causative organism False H. Influenza is a common causative organism in acute sinusitis. (c) E. Coli is a common organism E. Coli is not a common causative organism of acute sinusitis. (d) Strep Pyogenes is not a frequent causative organism Strep Pyogenes is a frequent causative organism of acute sinusitis as is strep pneumonia and H. influenza. (e) Metronidazole is first line therapy. Amoxicillin 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. Yellow fever is transmitted to humans by the bite of a mosquito. (b) Rabies is a DNA virus Rabies is an RNA rhabdovirus. (c) Infection by entry of larvae through skin- hookworm
MCEM Microbiology MCQ The larval form's of some helminths can survive in soil or water. (d) Faecal-oral spread - shigellosis Particularly among children in residential institutions. (e) Hep A is spread by inocculation
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Hep A is spread by ingestion of contaminated foods. 8. The common cold: (a) Rhinovirus is a rare causative organism. Rhinovirus and Coronavirus are the 2 most common pathogens accounting for 50% of cases (b) Coronavirus is not a common pathogen Rhinovirus 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. This is why the common cold is so common (d) Common colds are usually followed by lower respiratory tract infections Common colds are not usually followed by lower respiratory tract infections (e) Common colds are less frequent in the first few years of life Common 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 ) Streptococcus pneumonia is a common organism ( >40% of cases ) (b) Organisms that colonise the nasopharynx frequently cause acute otitis media. Microorganisms 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. Haemophilus influenza may cause up to 40% of cases. (d) Moraxella catarrhalis may cause acute otitis media in up to 15% of cases. Moraxella 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 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. Testicular 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. Is a complication of gonococcal urethritis and prostatitis (c) Is a manifestation of genital infection with ureaplasma spp
(d) Does not complicate the mumps virus. Orchitis may occasionally complicate the mumps virus.
MCEM Microbiology MCQ (e) Is not associated with tuberculosis.
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Epididymitis can be caused by mycobacterium tuberculosis. 11. Tetanus: (a) The exotoxin inhibits the release of GABA from presynaptic nerve terminals. The exotoxin inhibits the release of GABA and glycine from presynaptic nerve terminals (b) Tetanus is associated with muscular laxity. Tetanus is associated with muscular rigidity, violent muscular contractions and autonomic instability. (c) The incubation period is from 12 to 24 hours. The incubation period is from 1 day to 1 month. (d) There is an association between puncture wounds and tetanus. There is an association between puncture wounds and tetanus. (e) Minor abrasions cannot cause tetanus. Minor 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 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 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. Coagulase catalyses the conversion of fibrinogen to fibrin (d) Staph Aureus produces coagulase which breaks down host tissues. Staph 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. 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 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 Gram negative bacilli including E Coli, Klebsiella, and pseudomonas are common. (c) Common organisms for neutropaenic bacteraemia include staph. epidermidis. Gram positive cocci including staph epidermidis, staph aureus and strep viridans are common. (d) Common organisms for neutropaenic bacteraemia include strep. viridans Gram positive cocci including staph epidermidis, staph aureus and strep viridans are common. (e) Vancomycin should be considered for severe mucositis with neutropaenic
MCEM Microbiology MCQ bacteraemia. Vancomycin should be considered for severe mucositis with neutropaenic bacteraemia. 14. Otitis Externa: (a) Rarely relapses Frequently is chronic and relapsing. (b) Can occur in any age group And is characterised more by inflammation than infection ie a type of chronic dermatitis (c) Gram negative bacilli are rarely responsible. Proteus and pseudomonas. Candida and aspergillus also isolated. (d) Aural toilet and topical antibiotics such as polymyxin are an appropriate approach to management Aural toilet and topical antibiotics such as polymyxin are an appropriate approach to management (e) Pseudomonas infection in diabetics rarely requires treatment.
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Almost always requires treatment and can progress to meningitis. 15. The following are true: (a) The incubation period for shigella is 2-3 days. The incubation period for shigella is 2-3 days. (b) The incubation period for rotavirus is 1-4 weeks. The incubation period for rotavirus is 1-7 days. (c) The incubation period for giardia lamblia is 2-4 days. The incubation period for giardia lamblia is 1-4 weeks. (d) The incubation period for E Coli 12-72 hours The incubation period for E Coli 12-72 hours 16. Cat Bites: (a) Have low infection rates if untreated 50% (b) Have a high risk of developing tenosynovitis Due to long narrow teeth (c) Staphylococcus aureus is often associated with infection. Staphylococcus aureus is often associated with infection. (d) Pasteurella Multocida is often associated with infection. Pasteurella Multocida is often associated with infection. (e) Anaerobes are not associated with cat bites Anaerobes 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. Quinolones inhibit bacterial DNA gyrase. Erythromycin binds to the 50S ribosome
MCEM Microbiology MCQ interfering with protein synthesis. (b) Fluoroquinolones are less active than quinolones against pseudomonas and Chlamydia. Fluoroquinolones are more active than quinolones against pseudomonas and Chlamydia (c) Erythromycin is active against gram positive cocci, many anaerobes including bacteroides, mycoplasma and Chlamydia Erythromycin is active against gram positive cocci, many anaerobes not including bacteroides, mycoplasma and Chlamydia (d) Erythromycin does not cross the placenta Erythromycin crosses the placenta (e) Erythromycin is excreted in the bile
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Erythromycin is excreted in the bile 18. In necrotising fasciitis: (a) The most common sole organism is strep pyogenes The 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. Infection spreads along the deep fascial planes (c) Very rarely involves anaerobes. Anaerobes are commonly present in necrotising fasciitis. (d) Blood cultures are usually positive
(e) Antibiotics alone are generally sufficient. Effective treatment depends on early surgical resection of i nfected tissue. 19. Septicaemia: (a) Mortality is approximately 10% Around 30% of patients die directly or indirectly from sepiticaemia. (b) White Cell count <2000 is associated with a better outcome Low WBC's are associated with worse outcomes. (c) Corticosteroids should almost always be started. The 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 Hypotension at initial presentation is associated with a worse outcome. (e) Single pathogen infections generally have better outcome's. Polymicrobial infections are associated with worse outcomes. 20. Haemophilus Influenza: (a) Is a small gram negative bacillus Haemophilus Influenza is a small gram negative bacillus. (b) Is a pathogen in humans only Human pathogen only. (c) 50% of healthy people are carriers.
MCEM Microbiology MCQ 50% of healthy people are carriers (d) 25% of people carry encapsulated strains 5% of people carry encapsulated strains (e) Transmission is by direct contact or by inhalation of respiratory tract droplets. Transmission is by direct contact or by inhalation of respiratory tract droplets.
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MCEM Microbiology MCQ
