MCEM Microbiology MCQ1. 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. 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 Humans 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. Children 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. The 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 Acute otitis media, sinusitis and acute pneumonia are the most common infections related to strep pneumonia (e) S. Pneumonia is generally sensitive to rifampicin 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. 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. (c) Cefuroxime Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Fals e Fals e Fals e Or the insertion of ribbon gauze soaked with corticosteroid ear drops. Because of reports of ototoxicity topical aminoglycosides are contraindicated in cases of perforated eardrums. Acute sinusitis is a cause of localised tenderness. Acute Sinusitis Y: (a) Is not a cause of localised tenderness. (c) E. 6. influenza. (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. Amoxicillin is first line therapy for acute sinusitis. Influenza is not a common causative organism False H. (e) Metronidazole is first line therapy. Influenza is a common causative organism in acute sinusitis. (e) Ampicillin 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. Otitis Externa: (a) If there is associated peforation of the tympanic membrane the topical antibiotic of choice is an aminoglycoside. (c) If a systemic anti-bacterial is required flucloxacillin is the drug of choice for anti-pseudomonal activity. Coli is not a common causative organism of acute sinusitis. (c) Infection by entry of larvae through skin. 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. (e) Chloramphenicol is an appropriate choice for topical infections. (b) H. Yellow fever is transmitted to humans by the bite of a mosquito. (b) Rabies is a DNA virus Rabies is an RNA rhabdovirus. fever and facial pain. (b) An effective treatment is the insertion of ribbon gauze dressing soaked with aluminium acetate solution. (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. 10% of patients will not tolerate the vehicle in the chloramphenicol preparation ( propylene glycol ) due to hypersensitivity. Coli is a common organism E. 7.MCEM Microbiology MCQ But not early cephalosporins such as cephradine (d) Co-Amoxyclav Ampicillin and clavulinic acid. 5.hookworm Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Fals e Fals e Fals e Tru e Tru e Fals e Fals e Tru e Tru e Fals e Fals e Tru e Tru e Tru e Fals e Fals e Fals e . The following associations are correct: (a) Yellow fever is transmitted to humans by the bite of a mosquito. Microorganisms enter the middle ear via the eustachian tube which is shorter and more horizontal in young children. particularly in children younger than 6 months. 9. Haemophilus influenza may cause up to 40% of cases. (e) Hep A is spread by inocculation Hep A is spread by ingestion of contaminated foods. Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Fals e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e . Orchitis may occasionally complicate the mumps virus. Testicular torsion begins with sudden severe testicular pain while the pain of epididymo-orchitis is typically more gradual in onset.shigellosis Particularly among children in residential institutions. Chlamydia pneumoniae may be a 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. 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. Epididymo-orchitis: (a) Begins with sudden severe testicular pain. 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. (e) Chlamydia pneumoniae may be a causative organism.MCEM Microbiology MCQ The larval form's of some helminths can survive in soil or water. 10. (d) Moraxella catarrhalis may cause acute otitis media in up to 15% of cases. 8. (c) Haemophilus influenza may cause up to 40% of cases. Moraxella catarrhalis( 3rd commonest organism) may cause acute otitis media in up to 15% of cases. The common cold: (a) Rhinovirus is a rare causative organism. (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. (d) Faecal-oral spread . particularly in children younger than 6 months. is cavitating and has a high mortality. (d) Common organisms for neutropaenic bacteraemia include strep. (c) Common organisms for neutropaenic bacteraemia include staph. staph aureus and strep viridans are common. axilla or perineum Asymptomatic carriage of Staph Aureus is found in 40% of healthy people. (b) Common organisms for neutropaenic bacteraemia include E Coli Gram negative bacilli including E Coli. The exotoxin inhibits the release of GABA and glycine from presynaptic nerve terminals (b) Tetanus is associated with muscular laxity. progresses rapidly. There is an association between puncture wounds and tetanus. Minor abrasions can cause tetanus. Klebsiella. Tetanus is associated with muscular rigidity. in the skin. 12. Coagulase catalyses the conversion of fibrinogen to fibrin (d) Staph Aureus produces coagulase which breaks down host tissues. (c) The incubation period is from 12 to 24 hours. axilla or perineum (c) Catalase catalyses the conversion of fibrinogen to fibrin. 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. (e) Minor abrasions cannot cause tetanus. 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. and pseudomonas are common. viridans Gram positive cocci including staph epidermidis. Staph Aureus produces extracellular lytic enzymes ( e. is cavitating and has a high mortality 13. The incubation period is from 1 day to 1 month. (d) There is an association between puncture wounds and tetanus. staph aureus and strep viridans are common. violent muscular contractions and autonomic instability. Epididymitis can be caused by mycobacterium tuberculosis. (e) Vancomycin should be considered for severe mucositis with neutropaenic Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Tru Fals e Fals e Fals e Fals e Fals .g lipase ) which break down host tissues (e) Staphylococcus pneumonia follows influenza.MCEM Microbiology MCQ (e) Is not associated with tuberculosis. in the skin. 11. epidermidis. Tetanus: (a) The exotoxin inhibits the release of GABA from presynaptic nerve terminals. Staphylococcus pneumonia follows influenza. progresses rapidly. Gram positive cocci including staph epidermidis. 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. Vancomycin should be considered for severe mucositis with neutropaenic bacteraemia. (e) Anaerobes are not associated with cat bites Anaerobes are associated with cat bites. Candida and aspergillus also isolated. 15. Otitis Externa: (a) Rarely relapses Frequently is chronic and relapsing. 14. (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. (c) The incubation period for giardia lamblia is 2-4 days. Staphylococcus aureus . (d) Pasteurella Multocida is often associated with infection. Erythromycin binds to the 50S ribosome Tru e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e e e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e . Pasteurella Multocida is often associated with infection. Proteus and pseudomonas. (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.MCEM Microbiology MCQ bacteraemia. Almost always requires treatment and can progress to meningitis. Streptococcus. The incubation period for giardia lamblia is 1-4 weeks.Pasteurella Multocida . Quinolones inhibit bacterial DNA gyrase.enterobacter and anaerobes are associated with cat bites 17. The following are true: (a) The incubation period for shigella is 2-3 days. (d) The incubation period for E Coli 12-72 hours The incubation period for E Coli 12-72 hours 16. Antibiotics in clinical use: (a) Quinolones bind to the 50S ribosome interfering with protein synthesis. Staphylococcus aureus is often associated with infection.Klebsiella. The incubation period for rotavirus is 1-7 days. (b) The incubation period for rotavirus is 1-4 weeks. The incubation period for shigella is 2-3 days. The role of corticosteroids is not clearly defined and they should not always be started. many anaerobes including bacteroides. 20. Septicaemia: (a) Mortality is approximately 10% Around 30% of patients die directly or indirectly from sepiticaemia. Fluoroquinolones are more active than quinolones against pseudomonas and Chlamydia (c) Erythromycin is active against gram positive cocci. many anaerobes not including bacteroides. mycoplasma and Chlamydia Erythromycin is active against gram positive cocci. (d) Blood cultures are usually positive (e) Antibiotics alone are generally sufficient. (b) Fluoroquinolones are less active than quinolones against pseudomonas and Chlamydia. (c) 50% of healthy people are carriers. (d) Hypotension at initial presentation is associated with a worse outcome Hypotension at initial presentation is associated with a worse outcome. (c) Corticosteroids should almost always be started. Haemophilus Influenza: (a) Is a small gram negative bacillus Haemophilus Influenza is a small gram negative bacillus. (b) White Cell count <2000 is associated with a better outcome Low WBC's are associated with worse outcomes. (b) Infection is isolated to the epidermis and the dermis. Polymicrobial infections are associated with worse outcomes. mycoplasma and Chlamydia (d) Erythromycin does not cross the placenta Erythromycin crosses the placenta (e) Erythromycin is excreted in the bile Erythromycin is excreted in the bile 18. Infection spreads along the deep fascial planes (c) Very rarely involves anaerobes. (b) Is a pathogen in humans only Human pathogen only. (e) Single pathogen infections generally have better outcome's.MCEM Microbiology MCQ interfering with protein synthesis. Anaerobes are commonly present in necrotising fasciitis. 19. 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. Effective treatment depends on early surgical resection of infected tissue. Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Tru e Tru e Fals e Fals e Fals e Fals e Fals e Tru e Tru e Tru e Fals e Fals e Fals e . Transmission is by direct contact or by inhalation of respiratory tract droplets. Tru e Tru e Fals e Fals e .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. MCEM Microbiology MCQ .