Dermophyte

An overview of dermatophytes, their classification, and clinical significance

Dermatophytes are a group of fungi that cause infections of the skin, hair, and nails due to their ability to utilize keratin. These fungi are responsible for conditions commonly referred to as "ringworm" or "tinea." Dermatophytes are classified into three genera: Trichophyton, Microsporum, and Epidermophyton.

Classification

Dermatophytes are classified based on their natural habitat and the type of keratin they infect:

• Anthropophilic dermatophytes primarily infect humans and are transmitted through direct contact or via fomites. Examples include Trichophyton rubrum and Epidermophyton floccosum.
• Zoophilic dermatophytes primarily infect animals but can be transmitted to humans. Examples include Microsporum canis and Trichophyton verrucosum.
• Geophilic dermatophytes are found in soil and occasionally infect humans and animals. An example is Microsporum gypseum.

Pathogenesis

Dermatophytes invade the keratinized tissues of the host, such as the stratum corneum of the skin, hair shafts, and nails. They produce keratinases and other enzymes that allow them to digest keratin and colonize these tissues. The infection is usually superficial, but it can cause significant discomfort and cosmetic issues.

Clinical Manifestations

Dermatophyte infections are classified based on the site of infection:

• Tinea capitis: Infection of the scalp and hair, often seen in children.
• Tinea corporis: Infection of the body, commonly known as ringworm.
• Tinea cruris: Infection of the groin area, also known as jock itch.
• Tinea pedis: Infection of the feet, commonly referred to as athlete's foot.
• Tinea unguium: Infection of the nails, also known as onychomycosis.

Diagnosis

Diagnosis of dermatophyte infections is typically made through clinical examination and confirmed by laboratory tests. These may include:

• Microscopic examination: Skin scrapings, hair, or nail samples are treated with potassium hydroxide (KOH) and examined under a microscope for the presence of fungal hyphae.
• Culture: Samples are cultured on Sabouraud's dextrose agar to identify the specific dermatophyte species.
• Molecular methods: PCR and other molecular techniques can be used for rapid and specific identification.

Treatment

Treatment of dermatophyte infections depends on the site and severity of the infection. Options include:

• Topical antifungals: Such as clotrimazole, miconazole, and terbinafine, are effective for mild skin infections.
• Oral antifungals: Such as terbinafine, itraconazole, and griseofulvin, are used for more extensive infections or those involving hair and nails.

Prevention

Preventive measures include maintaining good personal hygiene, avoiding sharing personal items, and keeping skin dry and clean. In communal settings, such as gyms and swimming pools, wearing protective footwear can help prevent transmission.

Also see

• Fungal infection
• Tinea
• Onychomycosis
• Antifungal