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Chapter: Microbiology

Superficial mycoses and dermatomycoses

Thousands of fungi both yeasts and filamentous fungi are present in the environment.



Thousands of fungi both yeasts and filamentous fungi are present in the environment. About 100 of them cause disease in man and ani-mals. Only very few species like dermatophytes and Candida are trans-mitted from man to man. Generally the fungal infections are classified into superficial, cutaneous, subcutaneous, and systemic mycoses. In-fections of skin, hair and nails may be chronic and resistant to treatment but do not affect the general health of the patients.

Superficial mycosis

1. Tinea versicolor

Tinea versicolor is a mild infection of skin. The fungus Malassezia furfur grows in the stratum corneum of the skin as spherical thick-skinned budding cells and short, bent hyphe. It does not cause any pathological signs.

Fine browny scales appear on the chest, back, abdomen, neck and upper arm. In brown skinned people it produces white patches and in whites brown patches which are of cosmetic importance only.

2.  Tinea Nigra

     Tinea nigra is a condition in which blackish macular area appears on the palmar or plantar surface of the skin. This condition is caused by Exophiala werneckii. The infected skin can be removed mechani-cally or chemically.


3 Piedra

Black piedra is a condition in which black nodules are formed around the scalp hair by Piedraia hartae.

In white piedra, Trichosporon cutaneum causes the formation of soft, white nodules aroung axillary, pubic, beard and scalp hair


Dermatomycosis is also known as cutaneous mycosis. It is caused by dermatophytes. They infect superficial keratinized tissues such as skin, hair, and nails. They do not invade deeper tissues.

Dermatophytes are closely related fungi and are classified into three genera: 1. Trichophyton , 2. Microsporon 3.Epidermophyton.

These genera are identified by their characteristic morphology of micro and macro conidia produced on Sabouraud’s dextrose agar. The infection produced by dermatophytes is called Tinea. In Tinea corporis the infection is present in non-hairy, smooth skin.

In Tinea pedis infection is present in the inter digital spaces on feet. When the infection is present in the groin it is called Tinea cruris where as when seen on the headTit is called Tinea capitis. inea barbae is the infection of the beard hair, and Tinea unguium is infection of the nail.

Laboratory diagnosis

Specimens consists of both skin and nail scrapings and hair plucked from the involved areas. Specimens are examined in a drop of 10% KOH. In skin or nails, branching filaments or chains of arthrospores are seen. Specimens are also inoculated on SDA medium and the fungi identified

     Fungal skin infections are treated with miconazole cream or with griseofulvin.

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