Epidemiology of Disease Caused by Nontuberculous Mycobacteria

The clinically important nontuberculous mycobacteria include M. kansasii, M. genavense, M. marinum, M. simiae, M. scrofulaceum and M. szulgai, M. avium, M. haemophilum, M. intracellulare, M. malmoense, M. ulcerans, and M. xenopi, M. abscessus, M. chelonae, M. fortuitum, and (rarely) M. smegmatis. Four clinical syndromes account for nearly all cases: pulmonary disease, lymphadenitis, skin or soft tissue disease, and disseminated disease in AIDS. M. avium and M. intracellulare (known together as M. avium complex), are the most common causes of pulmonary disease, lymphadenitis, and disseminated disease. All four clinical syndromes seem to be increasing in frequency, particularly in immunosuppressed hosts. Nontuberculous mycobacteria are acquired from the environment, but specific reservoirs of these organisms leading to human disease have not been defined.