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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

Rippon (1988) accepted 22 species and four varieties in the genus Trichophyton based on morphology. DNA sequences now play a prominent role in delineating phylogenetic relationships, and as such species concepts in Trichophyton have changed. Fifteen species are now recognised in the genus. The descriptions and species concepts provided in this publication are based upon a combination of traditional morphological criteria and the current (2016) recognised phylogenetic species (de Hoog et al. 2016).

The genus Trichophyton is characterised morphologically 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 µm 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 µm in size. The presence of microconidia differentiates this genus from Epidermophyton, and the smooth-walled, mostly sessile macroconidia differentiates it from Lophophyton, Microsporum and Nannizzia.

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. eriotrephon, T. tonsurans, and to a lesser extent T. verrucosum, which may produce conidia on some media. In these species the shape, size and arrangement of the microconidia is the most important character. Culture characteristics are also useful.

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. Culture characteristics and clinical information such as the site, appearance of the lesion, geographic location, travel history, animal contacts and even occupation are most important.

Many laboratories have used growth on additional media and/or confirmatory tests to help differentiate between species of Trichophyton, especially isolates of T. rubrum, T. interdigitale, T. mentagrophytes and T. tonsurans. These include growth characteristics on media such as Littman oxgall agar, lactritmel agar, potato dextrose agar, Sabouraud’s agar with 5% Salt, 1% peptone agar, bromocresol purple-milk solids glucose agar (BCP), Trichophyton agars No. 1-5, hydrolysis of urea and hair perforation tests.

Molecular Identification: ITS and EF-1α sequencing is recommended for accurate species identification (Gräser et al. 1998, 1999b, 2000a, 2008; Irinyi et al. 2015; Mirhendi et al. 2015).

MALDI-TOF MS: Methods reported by Erhard et al. (2008), Nenoff et al. (2011), Cassange et al. (2011), l’Ollivier et al. (2013), Calderaro et al. (2014), Packeu et al. (2013, 2014).

References: Rebell and Taplin (1970), Ajello (1972), Vanbreusegham et al. (1978), Rippon (1988), McGinnis (1980), Domsch et al. (1980), Kane et al. (1997), Chen et al. (2011), de Hoog et al. (2000, 2015, 2016).


Trichophyton concentricum
Trichophyton equinum
Trichophyton eriotrephon
Trichophyton interdigitale
Trichophyton mentagrophytes
Trichophyton quinckeanum
Trichophyton rubrum
Trichophyton schoenleinii
Trichophyton soudanense
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