Module 13: Intro to Dermatophytes
Module 13.3: Three Most Common Veterinary Dermatophytes Observed on DTM
The three most common veterinary dermatophytes observed on DTM
In the laboratory you will be asked to identify the 3 most common dermatophytes commonly cultured on DTM; Microsporum canis, Microsporum gypseum, and a Trichophyton sp. Below are descriptions and images of those fungi.
Microsporum canis
The macroconidia are multicellular (5-15 cells), spindle-shaped with rough, thick-walled. The macroconidia have a terminal knob. They produce fewer macroconidia than M. gypseum.
![Microsporum canis](https://pressbooks.umn.edu/app/uploads/sites/104/2021/06/5-1.png)
Microsporum gypseum
The macroconidia are numerous, multicellular (4-6 cells), symmetrical, ellipsoidal, with thin walls. The ends of the macroconidia differ in shape. The distal end is rounded where the proximal end can be truncated from where it attached to hyphae.
![Microsporum gypseum](https://pressbooks.umn.edu/app/uploads/sites/104/2021/06/5-1.jpg)
Trichophyton sp.
The microconidia are single-celled, spherical in shape, and numerous. The macroconidia are cigar-shaped, multicellular (2-5 cells), thin-walled, and are rarely seen. These can be differentiated from M. canis as they have 6 compartments formed by the septae.
![Trichophyton sp.](https://pressbooks.umn.edu/app/uploads/sites/104/2021/06/6.gif)
Knowledge check
Key Takeaways
- Dermatophytes are common cutaneous fungal pathogens in all species
- Microsporum and Trichophyton are the 2 most common genera in veterinary medicine
- On DTM, the dermatophyte fungal colonies are buff in color and accompany a color change to red on the agar
- Saphyrophytic or contaminant fungi will grow on DTM, but do not routinely cause a color change and the colonies are not buff
- Microscopic evaluation of the colonies is an important step in the diagnosis and may influence the control steps based on the species of dermatophyte observed (i.e. geophilic vs. zoophilic)