Bacteriology USMLE Step 1 Practice Question
A 4-week-old laboratory mouse receives an intraperitoneal injection of live nonencapsulated Streptococcus pneumoniae mixed with heat-killed encapsulated strain. Within 48 hours, the mouse develops fever (39.2°C), tachycardia (180 bpm), and tachypnea (60 breaths/min). Blood culture yields live encapsulated S. pneumoniae; CSF shows elevated protein (180 mg/dL) without meningitis. Nonencapsulated bacteria are not recovered. Which genetic process best explains this transformation?
Answer choices
- AAntigenic shift
- BConjugation
- CTransduction
- DTransformationCorrect answer
- ETransposition
- FAntigenic drift
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