Other Medically Important Fungi

Pneumocystis carinii

• Unicellular eukaryote originally classified as protozoan, but currently described with the fungi in the ASM Manual of Clinical Microbiology 7th ed; the debate continues
• Cysts contain up to 8 ovoid-to-fusiform spores
• Free trophic forms are more common in clinical specimen, are 1.5-5μ and have small nuclei (0.5-1μ)
• Diagnosis still relies on morphologic identification of the organism from respiratory specimen
• In AIDS patients, 80% of PCP can be diagnosed on induced sputum; the remainder may need bronchoalveolar lavage
• At San Francisco General Hospital & Trauma Center specimen may be examined if the patient:
  1. is immunocompromised
  2. has respiratory symptoms and
  3. has objective evidence of lung disease

FIG. 1. Pneumocystis in induced sputum; wright stain stains trophozoites.

FIG. 2. Pneumocystis in induced sputum; wright stain stains trophozoites.

FIG. 3. Pneumocystis in bronchoalveolar lavage; toluidine blue highlights cyst forms.