A prospective evaluation of Mycobacterium avium complex colonization of the respiratory and gastrointestinal tracts of persons with human immunodeficiency virus infection.

To describe the natural history of Mycobacterium avium complex (MAC) in the respiratory or gastrointestinal tract of persons with human immunodeficiency virus (HIV) infection, 67 HIV-infected patients with CD4+ cell counts < 200/mm3 and initial negative MAC blood cultures were followed prospectively. Patients were screened every 3 months with cultures and smears of sputum, rectal swab, and blood for mycobacteria. Fourteen patients (20.9%) developed positive blood cultures for MAC (23.4%/year). Sputum cultures revealed MAC in 3 (21%) of the 14 patients at 1, 2, and 8 months before dissemination; no smears were positive. No rectal swab cultures or smears were positive before dissemination. Colonization of the respiratory and gastrointestinal tracts in persons with HIV infection and < 200/mm3 CD4+ cells is infrequently detected with currently available techniques. Screening cultures and smears of sputum and stool do not appear to be sensitive methods for detection of early MAC infection.