Microbiology

Athlete's foot and ringworm. Both athlete's foot and ringworm are caused by various species of fungi belonging to the genera Trichophyton, Microsporum, and Epidermophyton. These fungi are often called dermatophytes, and their diseases are referred to as dermatomycoses. Both diseases are accompanied by fluid‐filled lesions occurring on the body surface. The diseases are spread by fragments of fungal hyphae. Athlete's foot is also called tinea pedis, while ringworm may be called tinea corporis (ringworm of the body), tinea cruris (ringworm of the groin), or tinea capitis (ringworm of the scalp). Many pharmaceutical ointments are available to prevent spread of the disease, and the antibiotic griseofulvin is available by prescription.

Sporotrichosis. Sporotrichosis is caused by the fungus Sporothrix schenckii. The fungus is transmitted during skin wounds associated with thorns of rose or barberry bushes, as well as by contact with sphagnum moss. The disease is accompanied by a nodular mass at the site of entry; then it spreads to the lymphatic vessels and swelling (edema) follows. Hard, knotlike growths are found beneath the body surface. Potassium iodide and amphotericin B may be used for therapy.

Blastomycosis. Blastomycosis is a fungal disease due to Blastomyces dermatitidis. This fungus is transmitted from the lungs of an infected patient or from a wound. In a wound it causes pus‐filled lesions and multiple abscesses. A systemic form of blastomycosis may develop, with involvement of other organs. Amphotericin B is used for severe cases.

Candidiasis (yeast disease). The fungus Candida albicans is commonly found in the normal flora of numerous body tracts, but in compromised individuals, it may cause a superficial infection known as candidiasis or yeast disease. Yeast disease occurs in the vaginal tract and is accompanied by internal discomfort, pruritis (itching sensations), and sometimes, a discharge. Yeast disease often follows the destruction of lactobacilli in the vaginal tract. It can be treated with such drugs as miconazole, ketoconazole, and itraconazole.

Candida albicans may also cause infection in other skin locations. For example, thrush is a form of candidiasis in which patches of inflammation occur on the tongue and mucous membranes of the mouth. A skin infection called onchyosis occurs in individuals whose hands are in contact with water for long periods.

Swimmer's itch. Swimmer's itch is a skin infection due to tissue invasion by species of the flatworm Schistosoma. The schistosomes are not pathogenic of themselves, but they induce an allergic reaction that brings on the skin irritation and itching associated with the disease. Transmission occurs during swimming in contaminated waters.

Dracunculiasis. Dracunculiasis is a skin disease caused by the round‐worm Dracunculus medinensis. In this disease, the roundworms live in skin lesions and emerge through the lesions. In tropical countries, dracunculiasis is widespread, and relief from the disease consists of removing the roundworms through openings made in the lesions.