Fungi can also be grouped as either true pathogens, organisms that typically can cause human disease in healthy humans, or as opportunists. Examples of true, obligate pathogenic fungi include:
- Coccidioides immitis
- Histoplasma capsulatum
- Blastomyces dermatitidis
These obligate pathogens are known as dimorphic fungi because they have yeast and filamentous mold phases. They usually form the yeast phase at body temperature (35–37° C), and the mold form at 25–30° C). Procedures that help differentiate them from the saprophytic hyaline molds (which they could resemble microscopically) are growth in culture media containing cycloheximide, and they show positive reactions in antigen-specific nucleic acid probe assays.
This course will not cover these true pathogens, except in comparison to the hyaline molds, which can sometimes mimic their microscopic appearance.
