Observing the microscopic morphology of yeast colonies after inoculation to cornmeal agar with Tween 80 helps confirm the identification of a given species presumptively determined by one of the automated or kit systems. Cornmeal Agar is used to distinguish the various species of Candida and other yeasts by examining pseudohyphae, blastoconidia, chlamydoconidia, and arthroconidia.
After incubation, the agar plate is placed on a microscope stage and examined for growth, first examining under low power (10X), and then proceeding to the high dry (40X) objective.
Initial observations of the cornmeal agar will reveal whether or not the isolate produces pseudohyphae or hyphae.
- The presence of pseudohyphae and blastoconidia suggests the genus Candida. All Candida species, except Candida (Torulopsis) glabrata, produce pseudohyphae when grown on cornmeal agar. Note: Although Saccharomyces cerevisiae may produce rudimentary pseudohyphae on cornmeal agar, the formation of budding blastoconidia is the more typical form seen in laboratory cultures, and therefore, Saccharomyces cerevisiae should be placed in the category of not producing pseudohyphae on cornmeal agar.
- Yeasts that produce blastospores only include Candida glabrata, Cryptococcus, Rhodotorula, and Saccharomyces.
- The presence of true hyphae indicates the presence of Trichosporon, Blastoschizomyces capitatus, or Geotrichum.
