Wattle Pharmacy Prep

Microbiology
Practice questions with explanations

Microbiology belongs to Biomedical sciences, which makes up about 20% of the Overseas Pharmacist Readiness Assessment (OPRA®). Answer each question yourself before opening the explanation.

1. Which explains why viruses cannot be cultured on standard bacterial media?

  1. They do not contain nucleic acid
  2. They grow too quickly for culture
  3. They are too large to be captured
  4. They require living host cells to replicate, so cell culture, antigen detection or nucleic acid amplification is used instead
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D. They require living host cells to replicate, so cell culture, antigen detection or nucleic acid amplification is used instead

Diagnosis has largely moved to PCR, which is fast, sensitive and can detect multiple pathogens simultaneously. Its sensitivity brings its own interpretive problem: detecting viral nucleic acid does not always mean the virus is causing the current illness, since shedding can persist after recovery or reflect asymptomatic carriage.

2. Which explains why antibiotic susceptibility results may not predict clinical response?

  1. In vitro results have no relationship to outcome
  2. Breakpoints reflect achievable concentrations at typical sites, which may not apply to sanctuary sites, biofilm, abscesses or unusual dosing
  3. Susceptibility testing is always predictive
  4. Only resistance matters clinically
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B. Breakpoints reflect achievable concentrations at typical sites, which may not apply to sanctuary sites, biofilm, abscesses or unusual dosing

A urinary breakpoint reflects concentrations achieved in urine, not in blood or cerebrospinal fluid, which is why nitrofurantoin appears susceptible for an organism causing pyelonephritis yet fails. Abscesses, prosthetic material and intracellular organisms all create conditions the plate cannot reproduce.

3. Which statement about anaerobic bacteria is correct?

  1. They grow best in high oxygen concentrations
  2. They are all Gram-positive
  3. They are never involved in abscess formation
  4. They lack the enzymes to neutralise oxygen radicals, and infections involving them often arise from gut or oral flora
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D. They lack the enzymes to neutralise oxygen radicals, and infections involving them often arise from gut or oral flora

Obligate anaerobes lack superoxide dismutase and catalase, so oxygen is toxic to them. They dominate the colonic and oral flora, and infections such as intra-abdominal abscess, aspiration pneumonia and dental sepsis are typically polymicrobial with an anaerobic component. Metronidazole and clindamycin are the classic anaerobic agents; abscesses also need drainage, because antibiotic penetration into pus is poor.

These are 3 of the 60 questions on microbiology in the app.

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More topics in Biomedical sciences

Cardiovascular physiology and pathophysiology · Cell biology and biochemistry · Endocrine physiology · Gastrointestinal physiology · Haematology · Immunology · Musculoskeletal and skin · Neurophysiology · Renal physiology and fluid balance · Reproductive physiology · Respiratory physiology and pathophysiology