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Question 1
Correct
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A 28-year-old medical student ate a reheated Chinese takeaway and developed severe vomiting a few hours after.
What is the SINGLE MOST likely causative organism?
Your Answer: Bacillus cereus
Explanation:Bacillus cereusis is the correct answer. It is a Gram-positive, rod-shaped, beta-haemolytic bacterium that causes ‘fried rice syndrome’.
Hardy spores in rice can survive boiling. When left at room temperature for long periods prior to frying these spores germinate. The emetic enterotoxin-producing strains cause nausea and vomiting between 1 and 6 hours after consumption while the diarrheagenic enterotoxin-producing strains (commonly associated with ingestion of meat, vegetables and dairy products) causes abdominal pain and vomiting, which starts 8-12 hours after ingestion.
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This question is part of the following fields:
- Microbiology
- Specific Pathogen Groups
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Question 2
Incorrect
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A 60-year-old female with a past history of rheumatic fever and a prosthetic mitral valve presents to you with fever and an episode of expressive dysphasia that lasted around 30 minutes. There is no history of known drug allergies On examination you note a systolic murmur and you suspect it is infective endocarditis.
Which antibacterial agents would be the most appropriate to prescribe in this case?
Your Answer: Vancomycin, rifampicin and metronidazole
Correct Answer: Vancomycin, rifampicin and gentamicin
Explanation:Endocarditis is infective or non infective inflammation (marantic endocarditis) of the inner layer of the heart and it often involves the heart valves.
Risk factors include:
Prosthetic heart valves
Congenital heart defects
Prior history of endocarditis
Rheumatic fever
Illicit intravenous drug useIn the presentation of endocarditis, the following triad is often quoted:
Persistent fever
Embolic phenomena
New or changing murmurA combination of vancomycin, rifampicin and gentamicin is advised if the patient has a cardiac prostheses, is penicillin allergic, or if methicillin-resistant Staphylococcus aureus (MRSA) is suspected. In this case the patient has a prosthetic valve making this the most appropriate initial treatment regimen.
Flucloxacillin and gentamicin are current recommended by NICE and the BNF for the initial ‘blind’ therapy in endocarditis. This patient has prostheses and this is not the most appropriate initial treatment regimen.
Other features that may be present include heart failure, splenomegaly, finger clubbing, renal features (haematuria, proteinuria, nephritis), and vasculitic features (splinter haemorrhages, Osler’s nodes, Janeway lesions, Roth’s spots).
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This question is part of the following fields:
- Microbiology
- Specific Pathogen Groups
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Question 3
Incorrect
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Which patients are particularly susceptible to infection with herpes simplex, those with:
Your Answer:
Correct Answer: T-cell deficiency
Explanation:Cell-mediated immunity, especially the action of cytotoxic T-cells, is essential in the control of herpesvirus infections and patients with T-cell deficiency are at particular risk of reactivation and severe infection. T-cell deficiency may follow HIV infection, chemotherapy, corticosteroid therapy or organ transplantation.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 4
Incorrect
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Bordetella pertussis is spread via which of the following routes:
Your Answer:
Correct Answer: Respiratory droplet route
Explanation:Bordetella pertussis is a Gram negative coccobacillus that causes whooping cough. B. pertussis is spread via the respiratory droplet route and expresses fimbriae that aid their adhesion to the ciliated epithelium of the upper respiratory tract, and produce a number of exotoxins, causing the characteristic thickened bronchial secretions, paralysis of cilia and lymphocytosis.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 5
Incorrect
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How is measles primarily transmitted:
Your Answer:
Correct Answer: Respiratory droplet route
Explanation:Measles belongs to the paramyxoviridae group of viruses. The incubation period is 7-18 days (average 10) and it is spread by airborne or droplet transmission. The classical presentation is of a high fever with coryzal symptoms and photophobia with conjunctivitis often being present. The rash that is associated is a widespread erythematous maculopapular rash. Koplik spots are pathognomonic for measles, and are the presence of white lesions on the buccal mucosa.
Differential diagnoses would include:
Rubella
Roseola infantum (exanthem subitom)
Scarlet fever
Kawasaki disease
Erythema infectiosum (5thdisease)
Enterovirus
Infectious mononucleosis
Diagnosis can be confirmed by the following means:
Salivary swab for measles specific IgM
Serum sample for measles specific IgM
Salivary swab for RNA detection
Possible complications include:
Otitis media
Febrile convulsions
Pneumonia
Bronchiectasis
Diarrhoea
Meningitis
Encephalitis
Immunosuppression
Subacute sclerosing panencephalitis
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 6
Incorrect
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A 71-year-old woman is treated with co-amoxiclav for a chest infection but she returns 1 week later. Her chest infection has resolved but she developed a profuse, offensive smelling diarrhoea and abdominal cramps. You suspect Clostridium difficile associated diarrhoea (CDAD).
ONE of these statements is true concerning this diagnosis.Your Answer:
Correct Answer: The gold standard for the diagnosis of Clostridium difficile colitis is cytotoxin assay
Explanation:Clostridium difficile, a Gram-positive, anaerobic, spore forming bacteria is present in the gut of approximately 3% of healthy adults (2012 UK HPA estimates). Following use of broad spectrum antibiotics, which alter normal gut flora, Clostridium difficile associated diarrhoea (CDAD) occurs.
Alcohol hand gel is not effective against Clostridium Difficile spores. Hand washing with soap and water is very essential for healthcare workers who come in contact with it.
Currently, the gold standard for the diagnosis of Clostridium difficile colitis is cytotoxin assay. Stool culture to detect Clostridium difficile is not specific for pathogenic strains, is expensive and therefore not specific for a diagnosis of CDAD
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This question is part of the following fields:
- Microbiology
- Specific Pathogen Groups
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Question 7
Incorrect
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When a child has chickenpox, how long should he or she be off from school?
Your Answer:
Correct Answer: Until all vesicles have crusted over
Explanation:To avoid the spread of infection, infected patients should be isolated. All lesions should be crusted over before children return to nursery or school, even if the standard exclusion time is 5 days.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 8
Incorrect
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Infection with Campylobacter jejuni is one of the most common risk factors for which of the following conditions?
Your Answer:
Correct Answer: Guillain-Barre syndrome
Explanation:One of the most common risk factors for GBS is infection with Campylobacter jejuni, which causes diarrhoea.
Guillain-Barré syndrome (GBS) is a rare autoimmune disorder in which the body’s immune system attacks the nerves, resulting in muscle weakness and paralysis.
Infection with Streptococcus pyogenes can cause acute glomerulonephritis and rheumatic fever.
Haemolytic uraemic syndrome is commonly linked to E. coli infection.
Following measles infection, subacute sclerosing panencephalitis develops.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 9
Incorrect
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Which of the following microbes adheres to the genital mucosa using fimbriae:
Your Answer:
Correct Answer: Neisseria gonorrhoeae
Explanation:Infection of the genital mucosa by Neisseria gonorrhoeae involves attachment to and invasion of epithelial cells. Initial adherence of gonococci to columnar epithelial cells is mediated by type IV pili assembled from pilin subunit PilE proteins and pilus tip-associated PilC proteins, it then invades the epithelial layer, triggering a local acute inflammatory response.
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This question is part of the following fields:
- Microbiology
- Principles
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Question 10
Incorrect
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Which of the following is NOT typically present in the nasopharyngeal flora:
Your Answer:
Correct Answer: Bacteroides spp.
Explanation:Bacteroides spp. are typically found in the normal flora of the lower gastrointestinal tract. Species commonly found in the flora of the nasopharynx include: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Corynebacterium spp., Moraxella spp. and Candida spp.
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This question is part of the following fields:
- Microbiology
- Principles
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