Despite intensive studies of the Trichophyton mentagrophytes species complex, its taxonomy still causes confusion. In this study, more than 70 dermatophytes were analyzed based on nuc rDNA ITS1-5.8S-ITS2 (ITS), D1–D2 domains of nuc 28S rDNA (D1D2), and β-tubulin gene (TUBB) sequences to clarify phylogenetic relationships in the complex. This demonstrated that strains of the complex were divided into three major lineages with high statistical support: (i) T. benhamiae and related species; (ii) T. simii and two related species, T. quinckeanum and T. schoenleinii; and (iii) T. mentagrophytes, T. interdigitale, and related species. The major lineages could be further divided into 18 phylogroups, representing either individual species or phylogenetically distinct groups within species. Among strains of T. benhamiae, African isolates American Type Culture Collection (ATCC) 28064 and 28065 formed a phylogenetically distinct phylogroup from their type strain and were considered a distinct species. Strains of T. mentagrophytes were divided into at least four phylogroups based on combined sequence analysis, but some phylogroups showed closer relationships to T. interdigitale, T. equinum, and T. tonsurans when compared by individual genes. This indicates that identifying those species with one gene could lead to incorrect results. For rapid identification of those dermatophytes, each phylogroup was tested by matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrometry using a database with customized reference spectra of each phylogroup. This system was able to identify all the tested strains to species level with higher than 91% accuracy, except for strains of T. interdigitale. The three phylogroups of T. benhamiae were well distinguished from one another with high identification accuracy, whereas phylogroups of T. mentagrophytes were often cross-identified to one another or to T. interdigitale. Further research should improve identification accuracy for some species, but the results suggested that MALDI-TOF MS could be a rapid and efficient identification tool for closely related dermatophytes in the T. mentagrophytes species complex.

CorrespondenceSung-Oui Suh ssuh@atcc.org ATCC, 10801 University Blvd., Manassas, VA 20110, USA Trichosporon dermatis is a causative agent of several mycoses in immunocompromised patients but is often misidentified as Trichosporon mucoides due to their phenotypic resemblance. In order to evaluate the current identification keys for these species and to develop a rapid and reliable identification method, 11 strains of these yeasts were fully characterized in this study by traditional and advanced technologies. DNA sequences of the internal transcribed spacer (ITS), IGS1, and D1/D2 regions identified six of the yeasts as T. dermatis that were previously known as T. mucoides, including ATCC 204094 that has been used as the quality-control strain of T. mucoides for the VITEK 2 system and other commercial yeast identification kits. These two species could not be differentiated reliably by any previously known phenotypic keys for the species, such as growth patterns on ethylamine, phloroglucinol and tyramine, or by the VITEK 2 system. On the other hand, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) proved to be a rapid and reliable identification tool for the two closely related yeasts. With newly added superspectra from fully authenticated reference strains, the VITEK MS system using MALDI-TOF MS successfully separated strains of T. dermatis and T. mucoides at a similarity level of approximately 67 % for the mass spectra data, and could identify these strains at the species level with 100 % accuracy in repeated tests. Furthermore, the in vitro susceptibility results indicated that itraconazole, posaconazole and voriconazole were more effective against both T. mucoides and T. dermatis than the other antifungal agents tested in this study. INTRODUCTIONTrichosporon mucoides is a clinically important yeast species that causes disseminated infections (Boekhout & Guého, 2003; Guého et al., 1994). Since Guého et al. (1992) described the species to accommodate an atypical group of yeasts in Trichosporon beigelii, several studies have reported T. mucoides as a causative agent of white piedra and onychomycosis, as well as fungal septicaemia in humans (e.g. Capoor et al., 2013; Guého et al., 1994; de Hoog & Guého, 2005;Lacasse & Cleveland, 2009;Mayser et al., 1996). Trichosporon dermatis, a sibling species of T. mucoides, was recognized by Sugita et al. (2001a) from a yeast strain that was originally identified as Cryptococcus humicola but was later distinguished from the species sequence comparison of the D1/D2 region of the large subunit of the 28S rRNA gene. The yeast is often isolated from infected skin or the blood of immunocompromised patients (Fan et al., 2011; Hashino et al., 2013;Ruan et al., 2009; Sugita et al., 2001a) as well as from environmental samples, such as households with summer-type hypersensitivity pneumonitis patients or certain soils (Gujjari et al., 2011;Sugita, 2011; Sugita et al., 2001b). Both T. mucoides and T. dermatis are well recognized in the genus...