Is dermatophytosis a fungus?

What is mycology?

Mycology is the study of fungi.

What are dermatophyte 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:

• Trichophyton [abbreviated as "T"]
• Microsporum ["M"]
• Epidermophyton ["E"].

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:

• T. rubrum [most common in New Zealand]
• T. interdigitale
• T. tonsurans [very common in the USA]
• M. audouinii
• T. violaceum
• M. ferrugineum
• T. schoenleinii
• T. megninii
• T. soudanense
• T. yaoundei

Zoophilic organisms include:

• M. canis [originating from cats and dogs]
• T. equinum [originating from horses]
• T. erinacei [originating from hedgehogs and other animals]
• T. verrucosum [originating from cattle]
• M. nanum [originating from pigs]
• M. distortum [a variant of M. canis].

Geophilic organisms include:

• Nannizziagypsea
• M. fulvum.

How are dermatophyte fungi diagnosed?

Fungal infection may be suspected clinically or with the help of dermatoscopy. The presence of a dermatophyte infection is confirmed by:

• Microscopy and culture of skin scrapings
• Histopathological examination of skin or nail biopsy using periodic acid-Schiff [PAS] stains to reveal fungal elements
• Specific antigen tests using molecular biology techniques such as polymerase chain reaction.

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