Microbiology
Summary
Dermatophytes are fungi that infect the skin, hair, and nails, leading to various conditions collectively known as tinea. They are categorized into anthropophilic (human-loving), zoophilic (animal-loving)>, and geophilic (soil-loving) species. The three primary genera of dermatophytes are Trichophyton, Epidermophyton, and Microsporum.
The tinea infections are named based on the body part they affect: Tinea capitis on the scalp, tinea corporis on the body, tinea cruris in the groin (jock itch), and tinea pedis on the skin of the feet (athlete's foot). Diagnosis of these infections often involves a KOH prep of skin, hair, or nail samples. Some species of Microsporum may fluoresce under a Wood's lamp. Effective treatments for tinea infections often involve topical azoles such as clotrimazole. When dermatophytes infect the nails, it results in onychomycosis, which often requires oral medications like terbinafine or griseofulvin for effective treatment.
Lesson Outline
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FAQs
Dermatophytes are fungi that can cause skin infections commonly known as tinea infections or ringworm. Depending on the infected body site, they can lead to conditions such as tinea capitis (scalp), tinea corporis (body), tinea cruris (groin area, also known as "jock itch"), tinea pedis (feet, also known as "athlete's foot"), and onychomycosis (nails).
Topical azoles (like clotrimazole) and allylamines (like terbinafine) are commonly used for treatment of dermatophyte infections. In more severe or hard-to-treat infections, systemic treatment may be required, often with oral griseofulvin, terbinafine, or itraconazole.
Athlete's foot, or tinea pedis, is caused by dermatophyte fungus, particularly Trichophyton spp., that thrives in warm, moist environment. Infections often happen when walking barefoot in shared public spaces. Treatment typically involves the use of topical antifungal agents such as clotrimazole or terbinafine, and in serious cases, oral antifungal treatment such as griseofulvin may be used.
Tinea capitis is a scalp infection commonly caused by Trichophyton and Microsporum spp. Diagnosis typically involves microscopic examination of the infected hair and scalp scrapings. Wood's lamp examination can also be helpful, as it causes some species of Microsporum to fluoresce. It is generally treated with oral antifungal medications, such as griseofulvin or terbinafine, because topical treatments do not penetrate deep enough into the hair follicle.
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