Which Mycobacterium is most notably associated with patients with AIDS?

• A. M. kansasii
• B. M. avium-intracellulare complex
• C. M. marinum
• D. M. bovis

Answer: (B)

Mycobacterium avium complex (MAC) is the organism most notably associated with AIDS because it commonly causes disseminated disease in patients with advanced HIV infection. In this setting, MAC—encompassing M. avium and M. intracellulare—spreads beyond the lungs and can produce prolonged fever, night sweats, weight loss, anemia, and enlarged liver and spleen. The infection is often detected with acid-fast bacteria in blood or tissue cultures, reflecting its systemic nature.

Other non-tuberculous mycobacteria like M. kansasii typically present as a pulmonary disease that mimics tuberculosis, especially in those with underlying lung disease; M. marinum causes a localized skin infection from aquarium or aquatic exposures; and M. bovis causes TB-like disease usually acquired from unpasteurized dairy products. While these can occur in immunocompromised individuals, they are not as characteristically linked to AIDS as MAC.