- Trichophyton

Fungi of the genus Trichophyton are the commonest agents of dermatophytoses. They are especially signi–cant in nail infections but also invade as keratinized skin and hair causing ringworm infection.1,2 Because of differences in clinical associations and geographic distribution between species,3,4 accurate identi–cation is important for disease management and for epidemiological purposes including the investigation of case clusters.5,6

44.1.1.1 Morphological-Based Classification The genus Trichophyton was –rst established in 1845 with the description of Trichophyton tonsurans. Other species descriptions quickly followed; in the same year, Trichophyton schoenleinii was described as Oidium schoenleinii and

as Achorion schoenleinii and, in 1847, as Trichophyton mentagrophytes.1,7 The early literature is confused by the description of many new species often based on trivial differences in colony morphology. The discovery of Arthroderma uncinatum, the teleomorph of Trichophyton ajelloi, in 1959 led to the descriptions of the sexual states of many dermatophytes.7 In 1986, the teleomorph states of Microsporum and Trichophyton were consolidated into a single teleomorph genus Arthroderma (family Arthrodermataceae; order Onygenales). Based on morphological characteristics, Arthroderma was reported to contain four anamorph genera: Chrysosporium, Epidermophyton, Microsporum, and Trichophyton.8 A masterful review of the early literature, featuring many of the great names of dermatology/medical mycology such as David Gruby, Raymond Sabouraud, and Chester Emmons, is provided by Rippon7; 22 Trichophyton species were accepted representing the “state-of-the-art” phylogeny based on morphology. However, from this time

44.1 Introduction ..................................................................................................................................................................... 357 44.1.1 Classi–cation ........................................................................................................................................................ 357

44.1.1.1 Morphological-Based Classi–cation ..................................................................................................... 357 44.1.1.2 Molecular-Based Taxonomy ................................................................................................................. 358

44.1.2 Ecology and Epidemiology .................................................................................................................................. 358 44.1.2.1 Species Distribution .............................................................................................................................. 358 44.1.2.2 Disease Transmission ............................................................................................................................ 358

44.1.3 Speci–c Virulence Determinants ........................................................................................................................ 362 44.1.4 Clinical Manifestations ....................................................................................................................................... 362

44.1.4.1 Tinea Corporis and Tinea Cruris .......................................................................................................... 362 44.1.4.2 Tinea Pedis ............................................................................................................................................ 363 44.1.4.3 Tinea Capitis ......................................................................................................................................... 363 44.1.4.4 Tinea Unguium (Onychomycosis) ......................................................................................................... 363 Invasive Forms of Disease ................................................................................................................................... 363

44.1.5 Diagnosis of Trichophyton Infection ................................................................................................................... 363 44.1.5.1 Phenotypic-Based Methods .................................................................................................................. 363 44.1.5.2 Molecular-Based Diagnostic Methods .................................................................................................. 367

44.2 Methods ........................................................................................................................................................................... 368 44.2.1 Sample Preparation .............................................................................................................................................. 368

44.2.1.1 Sample Collection for Phenotypic and Molecular-Based Identi–cation ............................................... 368 44.2.1.2 Media and Culture Conditions .............................................................................................................. 369 44.2.1.3 DNA Extraction Protocols .................................................................................................................... 369

44.2.2 Detection Procedures ........................................................................................................................................... 370 44.2.2.1 Species Identi–cation Using ITS Sequence Analysis ........................................................................... 370 44.2.2.2 Genotyping of Trichoohyton spp. ......................................................................................................... 371

44.3 Conclusion and Perspectives ............................................................................................................................................ 372 References ................................................................................................................................................................................. 372

on, molecular biology has played the more important role in delineating phylogenetic relationships (Table 44.1).