General Comments

Over 30 recognized species of dermatophytes can infect skin, hair, and nails. The majority of dermatophyte infections in the United States are caused by 6 species: Epidermophyton floccosum, Microsporum canis,M. gypseum,Trichophyton mentagrophytes,T. rubrum, and T. tonsurans. All species produce delicate, narrow, hyaline hyphae.
Three genera comprise the dermatophytes. The following features are useful to help place a suspected dermatophyte into one of these genera:

Dermatophytes: Direct Examination of Hyphae

Microsporum canis

microsporum canis

FIG. 1. Microsporum canis in slide culture.

Microsporum gypseum

m. gypseum
microsporum gypseum

FIG. 1. Microsporum gypseum in slide culture. Multiple macroconidia are present.

FIG. 2. Microsporum gypseum in slide culture. Note that macroconidia are more numerous, less barrel-shaped, and contain fewer cells than M. canis.

microsporum gypseum

Microsporum audouinii

microsporum audouinii

FIG. 1. Microsporum audouinii in slide culture. Specific features can be difficult to obtain with this species. Final diagnosis may require consultation with a reference laboratory or expert.

Trichophyton verrucosum

trichophyton verrucosum

FIG. 1. Trichophyton verrucosum in slide culture.

FIG. 2. Trichophyton verrucosum in slide culture.

trichophyton verrucosum

Trichophyton tonsurans

t. tonsurans
trichophyton tonsurans

FIG. 1. Trichophyton tonsurans in slide culture.

FIG. 2. Trichophyton tonsurans in slide culture. Macroconidia, such as this one, are rare but may be present.


Trichophyton rubrum

trichophyton rubrum

FIG. 1. Trichophyton rubrum in slide culture. Pyriform microconidia are abundant in this culture.

Trichophyton mentagrophytes

t. mentagrophytes
trichophyton mentagrophytes

FIG. 1. Trichophyton mentagrophytes in slide culture.

FIG. 2. Trichophyton mentagrophytes in slide culture; macroconidia as seen here may occasionally be found. Also scattered within this photomicrograph are microconidia.

trichophyton mentagrophytes

Epidermophyton floccosum

e. floccosum
epidermophyton floccosum

FIG. 1. Epidermophyton floccosum in slide culture.

Trichophyton equinum

t. equinum
trichophyton equinum

FIG. 1. Trichophyton equinum in slide culture.

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Copyright © 2001, William McDonald, M.D.
Revised: 5 September 2002