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School of Molecular & Biomedical Science
The University of Adelaide
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Trichophyton sp.

Teleomorph: Arthroderma sp.

The genus Trichophyton is characterised by the development of both smooth-walled macro- and microconidia. Macroconidia are mostly borne laterally directly on the hyphae or on short pedicels, and are thin- or thick-walled, clavate to fusiform, and range from 4-8 x 8-50 mm in size. Macroconidia are few or absent in many species. Microconidia are spherical, pyriform to clavate or of irregular shape and range from 2-3 x 2-4 mm in size. The presence of microconidia distinguishes this genus from Epidermophyton and the smooth-walled, mostly sessile macroconidia separate it from Microsporum. Twenty species have been recognised, however only the more common species are included in these descriptions.

Note: species concepts in dermatophytes are currently in a state of flux. Recent molecular studies have shown that many species appear to be clonal and that there is little correlation between “genetic” and “phenotypic” species (Graser et al. 2006). The descriptions and species concepts provided in this publication are based on traditional morphological criteria which may not correspond to molecular identification results.

Trichophyton ajelloi
Trichophyton concentricum
Trichophyton equinum
Trichophyton erinacei
Trichophyton interdigitale
Trichophyton interditale var. nodulare
Trichophyton mentagrophytes
Trichophyton mentagrophytes var. quinckeanum
Trichophyton rubrum
Trichophyton rubrum downy strain
Trichophyton rubrum granular strain
Trichophyton schoenleinii
Trichophyton soudanense
Trichophyton terrestre
Trichophyton tonsurans
Trichophyton verrucosum
Trichophyton violaceum

 

MIC data is limited.  Antifungal susceptibility testing of individual strains is recommended.

Antifungal MIC ug/mL Antifungal
MIC ug/mL
Range
MIC90
Range
MIC90
Griseofulvin
0.06-4
1-2
Amphotericin B
0.03-16
0.5-1
Itraconazole
0.01-8
0.25-0.5
Fluconazole
0.05->64
32
Terbinafine
0.01-16
0.06
Voriconazole
0.007-8
0.25

 

The presence of microconidia distinguishes this genus from Epidermophyton and the smooth-walled, mostly sessile macroconidia separate it from Microsporum. Twenty species have been recognized, however in practice, two groups may be recognized on direct microscopy:

In practice, two groups may be recognised on direct microscopy:

1. Those species that usually produce microconidia, macroconidia may or may not be present i.e. T. rubrum, T. interdigitale, T. mentagrophytes, T. equinum, T. erinacei, T. tonsurans, T. terrestre and to a lesser extent T. verrucosum, which may produce conidia on some media; and

2. Those species that usually do not produce conidia. Chlamydospores or other hyphal structures may be present, but microscopy is generally non-diagnostic; i.e. T. verrucosum, T. violaceum, T. concentricum, T. schoenleinii and T. soudanense.

Many laboratories seem to have difficulty in distinguishing between species of Trichophyton, especially isolates of T. rubrum, T. interdigitale, T. mentagrophytes and T. tonsurans. Basically, the laboratories which consistently identify these fungi correctly do more work and use additional media and/or confirmatory tests. However, it must be stressed that no one single test is infallible, dermatophyte species are very variable organisms and many characteristics either overlap or are inconsistent.

The Mycology Unit at the Adelaide Women’s and Children’s Hospital uses a dermatophyte identification scheme, devised by the late Geraldine Kaminski, comprising 6 different media to help identify and differentiate the various species and strains of Trichophyton. The media in this scheme are Littman Oxgall agar, Lactritmel agar, Sabouraud’s agar with 5% NaCl, 1% Peptone agar, Trichophyton agar No. 1, and hydrolysis of urea (see appendix for details).

Kaminski's dermatophyte identification scheme pdf file

Practical Identification of Common Dermatophytes pdf file

T. rubrum on Kaminski's scheme
T. rubrum on Kaminski's scheme.

T. mentagrophytes var. interdigitale on Kaminski's scheme
T. mentagrophytes var. interdigitale on Kaminski's scheme.

Differentiation of T. mentagrophytes var. interdigitalefrom T. rubrum using Lactritmel agar
Differentiation of T. mentagrophytes var. interdigitalefrom T. rubrum using Lactritmel agar.

Urease test for differentiation
Urease test for the differentiation of T. mentagrophytes var. interdigitale [+7days] from T. rubrum [-7days].

Clinical significance:

The genus Trichophyton contains a number of important species that are the principle causative agents of animal and human dermatophytoses [tinea and ringworm].

Mycosis: Dermatophytosis

Further reading:

Rebell, G., and D. Taplin. 1970. The Dermatophytes. 2nd. revised edition. University of Miami Press, Coral Gables, Florida. USA.

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA.