The importance of vigorous treatment of and prophylaxis for opportunistic infections in patients with acquired immunodeficiency syndrome (AIDS) is stressed in a review by Weller and Williams. Pneumonia caused by Pneumocystis carinii is now usually found in newly diagnosed AIDS patients and those who have inadequate prophylactic therapy. Prompt diagnosis is important and may require bronchoscopy. Trimethoprim-sul-famethoxazole remains the first-line therapy for prophylaxis and acute treatment. Primary prophylaxis is indicated for all patients with CD4 counts below 200 per mm³ (200 × 10⁶ per L), but the rate of discontinuation is high because of side effects.

Toxoplasmosis infection most commonly affects the brain and is diagnosed by the characteristic ring of enhancing lesions on computed tomographic scan. Initial treatment with sulfadiazine plus pyrimethamine may have to be discontinued because of side effects. Clindamycin can be used as an alternative. Corticosteroids are frequently used to reduce cerebral edema. Patients with negative toxoplasma serology should be advised to avoid eating raw or undercooked meat and contact with cat feces. About one third of AIDS patients with positive toxoplasma serology and CD4 counts less than 100 per mm³ (100 × 10⁶ per L) develop cerebral infection within one year. Prophylaxis with trimethoprim-sulfamethoxazole or dapsone plus pyrimethamine is recommended. Bacterial resistance limits use of other agents such as clarithromycin and azithromycin.

Management of cryptosporidiosis is usually based on symptom control and use of antiviral therapy to increase the CD4 count because there is no effective specific treatment for this infection. Patients are frequently advised to use filters or boil water to minimize the risk of infection. Medications such as spiramycin, erythromycin, and azithromycin have been reported to be effective, and metronidazole can occasionally relieve diarrhea.

A variety of viral and fungal infections may occur in patients with AIDS. Prophylactic therapy has to be individualized and based on balancing the severity and frequency of infections with the side effects and danger of interactions between medications.

Management and prophylaxis of tuberculosis in AIDS patients is complicated by interactions between rifamycins and antiretrovirals. Tuberculosis in AIDS patients may be extra-pulmonary and resistant to several drugs. Prophylactic therapy significantly reduces mortality from disseminatedMycobacterium avium infection. Several regimens have been proposed, but weekly azithromycin plus daily rifabutin is probably the most effective prophylaxis regimen.