Bacterial Infections USMLE Step 1 Practice Question
A 61-year-old woman from Wisconsin presents 5 days after hiking in wooded terrain with fever (39.2°C), malaise, and confusion. Vital signs show HR 102/min, BP 128/82 mmHg, RR 18/min, SpO2 98% on room air. Laboratory studies reveal leukopenia (WBC 3.2 K/µL), thrombocytopenia (platelets 95 K/µL), and elevated transaminases (AST 156 U/L). Peripheral blood smear demonstrates intracellular morulae within neutrophils. Chest radiograph is unremarkable. Which organism is most likely responsible?
Answer choices
- APlasmodium falciparum
- BRickettsia rickettsii
- CEhrlichia chaffeensis
- DAnaplasma phagocytophilumCorrect answer
- EBorrelia burgdorferi
- FBabesia microti
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