6 / Molecular epidemiology of Trichophyton mentagrophytes – a new approach

Abstract

Objectives: According to the currently suggested classification and new taxonomy of the dermatophytes, the former Trichophyton (T.) mentagrophytes (TM)-complex is now differentiated in T. mentagrophytes (zoophilic strains) and Trichophyton interdigitale (TI, anthropophilic strains). Other species in this complex include T. quinckeanum as well as T. benhamiae (isolated from guinea pigs) and T. erinacei (found in hedgehogs). Patients and methods: In the period from 2015 to 2017, approximately 40 strains of TM and TI were investigated. These were both wild strains isolated from routine diagnostics at the laboratory Mu00f6lbis, Germany, and strains from patients returned from Thailand, Australia, and those from India. Strains from Iran were provided from Ali Rezaei-Matehkolaei. Sequences of reference strains from databases were used for comparison. All strains were preliminarily identified by conventional laboratory methods based on macroscopic and microscopic morphology. These findings were confirmed by analyses of the internal transcribed spacer 1 (ITS1), 5.8S, and ITS2 region rRNA sequences. In addition, sequencing using the target of the translation elongation factor (TEF)-1u03b1 gene was performed. The sequence of each strain was then compared to strains containing in databases. Based on the principle of similarity search (BLASTn search), individual strains were identified down to the species level by utilizing the validated Online Dermatophyte Database of the Westerdijk Fungal Biodiversity Institute (formerly Centraalbureau voor Schimmelcultures CBS), Utrecht, Netherlands (u201cwww.westerdijkinstitute.nlu201d). In addition, samples were compared with sequences obtained from the very comprehensive u2013 but not yet validated u2013 database of the National Center for Biotechnology Information (NCBI) in Bethesda, Maryland. The yielded sequences of the wild type and reference strains were used for comparative molecular analysis and the generation of dendrograms based on the ITS region and of the TEF-1u03b1 gene. Due to the data of sequencing genotyping of the strains according to geographic origin and to the animal source of infection was made. Results: Due to sequencing of the ITS region of the rDNA, altogether 8 different genotypes of TM and TI could be demonstrated. These clusters or genotypes are mostly associated to the geographic origin or to the source of infection. TI forms 2 groups: Type 1 (Europe) and Type 2 (Cosmopolite). In the species TM, however, altogether 6 different genotypes were formed. These were TM Germany Type 1 (Cosmopolite), Germany Type 2, Australia Type 1, u201cSnowleopardu201d Type 1 (Europe), Australia Type 1, Thailand Type 1, Iran Type 1, and India Type 1 (Asia and Oceania). Conclusion: Due to the recent change of the taxonomy of dermatophytes, the actually in databases deposited sequences of TI und TM do not allow an exact allocation to the respective species and genotype. Based on results of sequencing preferably of the ITS region of the rDNA, we are able to demonstrate that within the zoophilic species TM, every strain corresponds to one out of six clusters or genotypes. TI showed 2 genotypes, only. Each cluster seems to be specific for e.g. a geographic area, for a country, or for a distinct animal which represents the source of infection, speaking for a special way of transmission of the infection.