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School of Biological Sciences
The University of Adelaide
AUSTRALIA 5005

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Dr David Ellis
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Trichophyton tonsurans

Trichophyton tonsurans is an anthropophilic fungus with a worldwide distribution which causes inflammatory or chronic non-inflammatory finely scaling lesions of skin, nails and scalp. It is a common cause of tinea capitis in Australian Aborigines and African Americans. Invaded hairs show an endothrix infection and do not fluoresce under Wood’s ultra-violet light.

RG-2 organism.

Morphological Description: Colonies 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, (the sulfureum form which resembles Epidermophyton floccosum), to dark-brown. The reverse colour varies from yellow-brown to reddish-brown to deep mahogany. Hyphae are relatively broad, irregular, 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 on some cultures. Numerous swollen giant forms of microconidia and chlamydospores are produced in older cultures.

Confirmatory Tests:

Mycosel Agar: Chlamydospore-like structures produced by 5 days is characteristic of T. tonsurans (Mochizuki et al. 2013).

Hydrolysis of Urea: positive at 5 days.


T. tonsurans showing good growth on T4 agar indicating a requirement for thiamine.

Nutritional Tests on Trichophyton Agars: results demonstrate a partial requirement for (a) thiamine. T1 = vitamin free agar, (b) T4 = vitamin free + thiamine agar.

Hair Perforation Test: Positive within 14 days.

Key Features: microscopic morphology, culture characteristics, endothrix invasion of hairs and partial thiamine requirement.

References: Rebell and Taplin (1970), Ajello (1972), Vanbreusegham et al. (1978), Rippon (1988), McGinnis (1980), Domsch et al. (1980), Kane et al. (1997) and de Hoog et al. (2000, 2015).

 


Trichophyton tonsurans cultures show considerable variation in texture and colour. The colour may vary from pale-buff to yellow to dark-brown. The reverse colour varies from yellow-brown to reddish-brown to deep mahogany.


Trichophyton tonsurans hyphae, microconidia and macroconidia.

 

Mycosis: Dermatophytosis