Comparison of methenamine silver nitrate and Giemsa stain for detection of Pneumocystis carinii in bronchoalveolar lavage specimens from HIV infected patients.

Seventy-seven bronchoalveolar lavages from human immunosuppressive virus infected patients with pulmonary symptoms were examined routinely for the presence of Pneumocystis carinii, using Giemsa stain to detect trophozoites and methenamine silver nitrate to detect cysts. Thirty-seven samples were found positive with both methods, but a further 10 were diagnosed with Giemsa indicating that the trophozoite stain is more sensitive. As Giemsa stain is simple, quick, cheap and familiar to most microbiological laboratories it should be used for screening of samples to be examined for Pneumocystis carinii. In cases where trophozoites are not detected by Giemsa a supplementary cyst stain may be performed in order to rule out the presumably few cases where cysts are present as the only evidence of Pneumocystis carinii infection.