Bacteriology USMLE Step 1 Practice Question
A 61-year-old woman on mechanical ventilation for 8 days develops fever (38.9°C), tachycardia (HR 112), and purulent sputum. Chest X-ray shows new bilateral infiltrates. Sputum culture grows a non-lactose fermenting, oxidase-positive gram-negative rod. The organism produces a toxin inactivating elongation factor 2 through ADP-ribosylation. Blood cultures remain negative. The patient has received appropriate empiric antibiotics for 48 hours without clinical improvement. Which organism is most likely responsible?
Answer choices
- ABordetella pertussis
- BNeisseria meningitidis
- CPseudomonas aeruginosaCorrect answer
- DEscherichia coli
- EVibrio cholerae
- FCorynebacterium diphtheriae
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