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Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2003.
Mycology is the study of fungi.
Dermatophyte fungi are the ringworm fungi (tinea). They depend on their host, which may be an animal ("zoophilic") or a human ("anthropophilic") and need to spread from one host to another to survive. Dermatophytes may also prefer to live in the soil ("geophilic").
Anthropophilic dermatophytes are so well adapted to living on human skin that they provoke a minimal inflammatory reaction. Zoophilic or geophilic dermatophytes will often provoke a more vigorous inflammatory reaction when they attempt to invade human skin.
There are nine genera of dermatophytes, recognised by the nature of their macroconidae (asexual spores). The common dermatophytes infecting humans are:
Other genera are Arthroderma, Ctenomyces, Lophophyton, Nannizzia, Guarromyces and Paraphyton.
There are about 50 species. Their spores can live for more than a year in human skin scales in the environment.
Anthropophilic organisms include:
Zoophilic organisms include:
Geophilic organisms include:
Fungal infection may be suspected clinically or with the help of dermatoscopy. The presence of a dermatophyte infection is confirmed by:
Microscopy showing dermatophyte fungal elements
Non-inoculated skin scraping slopes. Blue top is Sabouraud dextrose agar with antibiotics and white top is Dermatophyte test medium.
Trichophyton rubrum colony morphology on potato dextrose agar culture plates showing reddish pigmentation at the back of the slope.
Trichophyton mentagrophytes cultured in Sabouraud dextrose agar slope with antibiotics.
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