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Mould Identification: A Virtual Self Assessment

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Unknown 27 = Trichophyton tonsurans

Case History
A 40-year-old man presented with a discoloured and thickened finger nail. Nail scrapings were taken and hyphal elements were observed on direct microscopy and the culture shown below was grown.
Clinical Appearance

T. tonsurans infection of a nail (tinea unguium).
Direct Microscopy (H&E)

Hyphal elements of T. tonsurans ramifying through skin scales mounted in 10% KOH and Parker ink solution.
Culture

Cultures of T. tonsurans show considerable variation in texture and colour. They may be suede-like to powdery, flat with a raised centre or folded, often with radial grooves. The colour may vary from pale-buff to yellow, which may resemble Epidermophyton floccosum, to dark-brown.  The reverse colour varies from yellow-brown to reddish-brown to deep mahogany.
Microscopy

The hyphae are relatively broad, irregular and much branched with numerous septa.  Numerous characteristic microconidia varying in size and shape from long-clavate to broad-pyriform are borne at right angles to the hyphae, which often remain unstained by lactophenol cotton blue.

Very occasional smooth, thin-walled, irregular, clavate macroconidia may be present in some cultures (slide 296).  Numerous swollen giant forms of microconidia and chlamydoconidia are produced in older cultures.
Key Features:  Microscopic morphology culture characteristics, endothrix invasion of hairs and partial thiamine requirements.

Comment: Trichophyton tonsurans is an anthropophilic fungus causing inflammatory or chronic non-inflammatory finely scaling lesions of skin, nails and scalp.  A common cause of tinea capitis in the Australian Aborigine and in the African-American population. Invaded hairs show an endothrix infection and do not fluoresce under Wood's ultra-violet light.

About Trichophyton Back to Virtual Assessment

What is your identification?

Trichophyton tonsurans

Epidermophyton floccosum
Trichophyton mentagrophytes

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