Microbiology - Microsporum Species

Microsporum is a genus of filamentous fungi (molds) that belongs to the dermatophyte group. Important species include Microsporum audouinii and Microsporum canis, along with several other species. These fungi mainly infect keratinized tissues, particularly the skin and hair, although nail infection may occasionally occur.

Microsporum infections occur worldwide. Some species are associated with animals; for example, M. canis is commonly linked to cats and dogs and can be transmitted to humans. The incubation period is variable and is not always clearly defined.

Microsporum can cause different forms of tinea (dermatophytosis), including tinea capitis of the scalp and hair, tinea corporis of the body, and tinea faciei of the face. Nail infection or onychomycosis is less commonly caused by Microsporum compared with other dermatophytes.

Diagnosis is made by collecting skin scrapings or infected hairs from the lesion. The fungus may then be identified using direct microscopic examination, fungal culture, or other laboratory methods.

Treatment depends on the site of infection. Localized skin infections may be treated with topical terbinafine, usually for several weeks. Tinea capitis generally requires oral antifungal therapy because topical treatment alone does not penetrate the infected hair follicles adequately. Oral agents may include griseofulvin, terbinafine, or itraconazole, depending on the organism and clinical situation.

If onychomycosis occurs, treatment is usually prolonged and may continue for several months. Itraconazole may also be used for certain dermatophyte infections, particularly when topical treatment is not sufficient.