Molecular taxonomy of Trichophyton mentagrophytes and T. tonsurans

Abstract

Most members of the anamorph genus Trichophyton are anthropophilic and have evolved with the human host. Classical parameters for the identification of dermatophytes include clinical features, cultural characteristics, conidial morphology and physiological test results. Phenotypic variability and pleomorphism due to culturing on artifical media is common among this group of organisms and has led to the description of numerous species. The validity of taxa around T. mentagrophytes and T. tonsurans was verified. Morphological and physiological features were compared to results of three different molecular techniques (sequencing of the internal transcribed spacer (ITS) region of the ribosomal operon, PCR fingerprinting and amplified fragment length polymorphism (AFLP) analysis). Twenty‐four species or varieties investigated could be reduced to five taxa and were reclassified or synonymized as Trichophyton tonsurans, T. interdigitale, T. mentagrophytes, T. simii and T. erinacei.

Phylogenetic analysis of Trichophyton mentagrophytes human and animal isolates based on MnSOD and ITS sequence comparison

“…They were identified on the basis of microscopy and colony characteristics and were classified using the following criteria: (i) clinical criteria (body localization, associated or not with clinical signs or symptoms of dermatophytosis), (ii) cultural aspects (texture, front and reverse colour of the colonies), and (iii) microscopic features (subspherical or clavate microconidia, macroconidia, spiral hyphae, and dense branchlets at right angles) (Graser et al, 1999b;Mochizuki et al, 1996Mochizuki et al, , 2003Ninet et al, 2003). Morphological data for the isolates, and their origins, are listed in under a laminar-airflow hood to avoid contamination.…”

“…These accurate molecular studies emerged as a critical issue for comprehensive understanding of the clinical and epidemiological implications of the genetic heterogeneity of T. mentagrophytes and resulted in the re-establishment of three if not four species: Trichophyton interdigitale close to the teleomorph Arthroderma vanbreuseghemii, T. mentagrophytes close to the teleomorph A. simii, and T. erinacei, plus another Trichophyon anamorph, both close to the teleomorph A. benhamiae, which includes both European-American and African races (Graser et al 1999b;Probst et al, 2002;Takahashi et al, 2003;Nenoff et al, 2007). Among these four species, two were rooted in typification, according to the criteria of the International Code of Botanical Nomenclature: T. mentagrophytes (strain CBS 318.56) and T. interdigitale (strain CBS 428.63) (Graser et al, 1999b).…”

“…More recently, sequence analysis of the rDNA regions (Graser et al, 1999a;Harmsen et al, 1995;Makimura et al, 1998Makimura et al, , 1999Mochizuki et al, 1999Mochizuki et al, , 2003 and, in particular, analysis of internal transcribed spacer (ITS) regions (Graser et al, 1999a;Makimura et al, 1998Makimura et al, , 1999Mochizuki et al, 1999), which appeared more suitable than the gene coding for the small-subunit rRNA (18S rRNA) (Harmsen et al, 1995), were used successfully to evaluate the phylogenetic relationships within the T. mentagrophytes complex. These accurate molecular studies emerged as a critical issue for comprehensive understanding of the clinical and epidemiological implications of the genetic heterogeneity of T. mentagrophytes and resulted in the re-establishment of three if not four species: Trichophyton interdigitale close to the teleomorph Arthroderma vanbreuseghemii, T. mentagrophytes close to the teleomorph A. simii, and T. erinacei, plus another Trichophyon anamorph, both close to the teleomorph A. benhamiae, which includes both European-American and African races (Graser et al 1999b;Probst et al, 2002;Takahashi et al, 2003;Nenoff et al, 2007). Among these four species, two were rooted in typification, according to the criteria of the International Code of Botanical Nomenclature: T. mentagrophytes (strain CBS 318.56) and T. interdigitale (strain CBS 428.63) (Graser et al, 1999b).…”

“…The species included in this anthropo-zoophilic complex, which were first defined on the basis of morphological features and mating-type studies, have more recently been investigated using molecular methods, revealing an organization more complex than expected. These molecular approaches have been based primarily on the G+C content of chromosomal DNA (Davison et al, 1980), total DNA homology (Davison & Mackenzie, 1984), restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) (Mochizuki et al, 1990(Mochizuki et al, , 1996, arbitrarily primed PCR (AP-PCR) (Liu et al, 2000), random amplification of polymorphic DNA (RAPD) analysis (Kac et al, 1999;Liu et al, 1997;Mochizuki et al, 1997) and PCR fingerprinting (Faggi et al, 2001;Graser et al, 1999b). More recently, sequence analysis of the rDNA regions (Graser et al, 1999a;Harmsen et al, 1995;Makimura et al, 1998Makimura et al, , 1999Mochizuki et al, 1999Mochizuki et al, , 2003 and, in particular, analysis of internal transcribed spacer (ITS) regions (Graser et al, 1999a;Makimura et al, 1998Makimura et al, , 1999Mochizuki et al, 1999), which appeared more suitable than the gene coding for the small-subunit rRNA (18S rRNA) (Harmsen et al, 1995), were used successfully to evaluate the phylogenetic relationships within the T. mentagrophytes complex.…”

Which Fungus Originally was Trichophyton mentagrophytes? Historical Review and Illustration by a Clinical Case

“…Identification of the dermatophyte species responsible for this sycosis as A. vanbreuseghemii gives support to a response to the question about which fungus should be really called T. mentagrophytes. A confusion came from the recent choice of the dermatophyte strain CBS 318.56 isolated from a human suppurative infection to designate a neotype of T. mentagrophytes [15]. The ITS and 28S sequences of this neotype strain were found to be identical to those of T. quinckeanum, which is an agent of smouse and human favus [5,16] while, based on Gruby's description, T. mentagrophytes senso stricto should have been reserved for a dermatophyte causing a sycosis.…”