A Study of Rifabutin, Used Alone or With Ethambutol in the Prevention of Mycobacterium Avium Complex (MAC) Bacteremia in Patients With AIDS

Inclusion Criteria Concurrent Medication: Required: * AZT, d4T, ddI, or ddC. * Antipneumocystis prophylaxis. Allowed: * Short course (\< 14 days) of ciprofloxacin for acute infections. Patients must have: * AIDS. * CD4 count \<= 100 cells/mm3. * NO prior or current MAC infection. Prior Medication: Required: * Antipneumocystis prophylaxis for at least 4 weeks prior to study entry. Allowed: * Prior rifabutin. * Prior ethambutol. * Prior clarithromycin. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Positive tuberculin skin test (PPD \> 5 mm). * Active M. tuberculosis. * Perceived as unreliable or unavailable for frequent monitoring. Concurrent Medication: Excluded: * Other antiretrovirals not specifically allowed. * All investigational drugs. * Other antimycobacterial therapy, such as clarithromycin, azithromycin, rifampin, clofazimine, amikacin, streptomycin, isoniazid, cycloserine, ethionamide, and ciprofloxacin (\>= 14 days). Patients with the following prior conditions are excluded: Known hypersensitivity to rifabutin, rifampin, or other rifamycins and/or ethambutol. Prior Medication: Excluded within 4 weeks prior to study entry: * Rifampin. * Isoniazid. * Clofazimine. * Cycloserine. * Ethionamide. * Amikacin. * Ciprofloxacin.