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Nocardiosis — ABIM Board MCQ

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HardInfectious DiseaseNocardiosisABIM Board

A 58-year-old sheep farmer with a prosthetic aortic valve has five months of fever, weight loss, negative routine blood cultures, and new paravalvular regurgitation. Coxiella burnetii phase I IgG is markedly elevated. Which antimicrobial strategy is most appropriate?

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Correct answer: E — Use prolonged doxycycline plus hydroxychloroquine with phase I serologic monitoring

The best answer is “Use prolonged doxycycline plus hydroxychloroquine with phase I serologic monitoring”. This is chronic Q-fever endocarditis, which requires prolonged combination therapy rather than the short doxycycline course used for acute Q fever. Hydroxychloroquine alkalinizes the Coxiella-containing phagolysosome and improves doxycycline activity. Treatment commonly lasts at least 18 months and requires specialist follow-up of phase I serology, drug toxicity, electrocardiography, and ophthalmologic risk. Conventional culture-negative regimens do not eradicate persistent Coxiella infection.

Reference: CDC: Diagnosis and Management of Q Fever—United States: https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6203a1.htm