Non-Human elements - Yeast cells

Budding Yeast
Trichrome stain x 1000

Yeast may resemble protozoan cysts (4-6 mm)

They are uniform in colour, have few inclusions and no nucleus.

Budding forms may be seen

Yeast
Gomori methenamine stain
x 1000

Note the thick cell wall.
The typical cup-shaped appearance of Pneumocystis carinii is lacking.
Also, PCP does not form hyphae as shown in the figure on the left.

Yeast could be confused with small protozoans like E. nana or with Cryptosporidium or Cyclospora oocysts in wet preparation.

The coccidian should always be confirmed with the modified-Kinyoun acid-fast stain. In the acid-fast stain, the oocysts of Cryptosporidium and Cyclospora species stain pink to red. Yeasts are not acid fast and stain green.