Pneumocystis pneumonia is an opportunistic infection caused by Pneumocystis carinii. Which of the following statements are true?

B. Pneumocystis pneumonia is the most common opportunistic infection in patients with AIDS.

C. The diagnosis of Pneumocystis pneumonia depends on the demonstration of P. carinii organisms in lung tissue.

DISCUSSION: P. carinii is a protozoan that stains with silver methenamine and resembles a fungus. It responds to antiprotozoal drugs. Pneumocystis pneumonia occurs in 80% of AIDS patients. The diagnosis is made by demonstrating the organisms in lung tissue by transbronchoscopic lung or brush biopsy, percutaneous needle biopsy, or open lung biopsy. Both trimethoprin-sulfamethoxazole and pentamidine isethionate are effective against P. carinii.