The primary objective of this trial is to assess the safety and the relative benefit of rifabutin monotherapy in preventing or delaying the incidence of Mycobacterium avium complex (MAC) bacteremia in AIDS patients with CD4 counts less than or equal to 200, as compared to placebo, and to assess if survival is prolonged in patients who receive rifabutin prophylaxis.

Inclusion Criteria

Patients must have the following:

• Diagnosis of AIDS with a case defining infection other than Mycobacterium avium complex (MAC).
• Written informed consent obtained, which must include a statement that treatment may involve risks to the embryo or fetus, which are currently unforeseeable, if the subject becomes pregnant.

Exclusion Criteria

Co-existing Condition:

Patients with the following conditions or symptoms are excluded:

• Known hypersensitivity to rifabutin, rifampin, other rifamycins, zidovudine or didanosine (ddI).
• Previous or current infection due to Mycobacterium avium complex (MAC) disease as evaluated by two successive blood cultures and two successive stool cultures taken within 14 days prior to study initiation.

Concurrent Medication:

Excluded:

• Antiretroviral agents other than zidovudine (AZT).
• Didanosine (ddI).
• Antimycobacterial therapy.
• Rifampin.
• Isoniazid.
• Clofazimine.
• Ethambutol.
• Cycloserine.
• Ethionamide.
• Amikacin.
• Ciprofloxacin.
• Streptomycin.
• Other investigational drugs.
• If antimicrobial therapy is required to treat bacterial infections (= or < 14 days), Adria Laboratories must be contacted prior to initiation of therapy.

Patients with the following are excluded:

• Known hypersensitivity to rifabutin, rifampin, other rifamycins, zidovudine (AZT), or didanosine (ddI).
• Previous or current Mycobacterium avium complex (MAC) infection.
• Perceived patient unreliability or unavailability for frequent monitoring.

Prior Medication:

Excluded within 4 weeks of study entry:

• Antiretroviral agents other than zidovudine (AZT) or didanosine (ddI).
• Antimycobacterial therapy.
• Rifampin.
• Isoniazid.
• Clofazimine.
• Ethambutol.
• Cycloserine.
• Ethionamide.
• Amikacin.
• Ciprofloxacin.

Required:

• Zidovudine (AZT).
• Antipneumocystis prophylactic therapy.

Required for at least 4 weeks prior to study entry:

• Zidovudine (AZT) or didanosine (ddI).
• Antipneumocystis prophylaxis.