Techniques for examining Pneumocystis carinii in fresh specimens.

Pneumocystis carinii was examined in fresh preparations of infected rat lung homogenates and tissue culture supernatants by a variety of light microscope techniques, vital dyes, and histologic stains. Phase-contrast microscopy, Nomarski interference-contrast microscopy, and bright-field microscopy with oblique illumination provided excellent views of P. carinii. Erythrosin B, and to a lesser extent trypan blue, were helpful in assessing organism viability. The use of Triton X-100-Giemsa stain permitted differentiation of the developmental stages in the P. carinii life cycle. The techniques developed here are easily adaptable to the microbiology laboratory and thus should have important clinical and research applications.