Mycobacterium kansasii causes pulmonary disease resembling TB in immunocompromised patients. Which antibiotic regimen is recommended for M. kansasii pulmonary disease?

• A Standard four-drug HRZE regimen for 6 months
• B Azithromycin + ethambutol + rifabutin for 12 months
• C Rifampicin + ethambutol + isoniazid for 12 months (minimum) based on susceptibility ✓
• D Imipenem + amikacin for 6 months

Explanation

M. kansasii is intrinsically resistant to pyrazinamide but susceptible to rifampicin, ethambutol, and isoniazid. ATS/IDSA guidelines recommend rifampicin-based regimen (rifampicin + ethambutol + isoniazid) for at least 12 months (or 12 months of negative cultures) for pulmonary M. kansasii disease. Rifampicin susceptibility is the key predictor of treatment success. The azithromycin-based regimen is used for M. avium complex (MAC) lung disease, not M. kansasii. Standard HRZE for 6 months is insufficient due to pyrazinamide intrinsic resistance.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

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