Identification of Trichophyton mentagrophytes strains isolated from patients with dermatophytosis

According to epidemiological, clinical and mycological criteria, it has long been admitted that the Trichophyton mentagrophytes species includes two varieties: a zoophilic variety (var. mentagrophytes) and an anthropophilic variety (var. interdigital) that involve the upper and the lower part of the body respectively. The further application of molecular techniques to the characterization of dermatophyte strains showed that this classification is unreliable. The aim of our study was to assess the usefulness of PCR-RFLP (restriction fragment length polymorphism) and sequencing in the characterization of T. mentagrophytes strains taken from Tunisian patients. The study was carried out in 2008 in the laboratory of Parasitology-Mycology of Farhat Hatched hospital, Sousse, Tunisia. A total of 133 strains were isolated from 133 patients addressed to the laboratory for dermatological lesions very evocative of dermatomycosis. Eighty strains were isolated from lesions located on the lower part of the body (onychomycosis, tinea pedis) and 53 strains from the upper part of the body (tinea capitis, tinea corporis). All strains were submitted to mycological examination (direct microscopic examination, and culture on Sabered medium) and further investigated by using RFLP analysis of the PCR amplified ITS1-5.8 s and ITS2 region of the ribosomal DNA and the MvaI restriction enzyme. In addition, 20 strains were further submitted to a sequencing of the ITS1-5.8 s and ITS2 region. On the basis of mycological criteria all strains were diagnosed as T. mentagrophytes. All strains produced the same RFLP pattern and were identified as T. mentagrophytes interdigital regardless of the location of lesions. Out of the 20 sequenced strains, five were found anthropophilic and 15 were zoophilic. In conclusion, all strains provisionally diagnosed as T. mentagrophytes on the basis of mycological criteria were shown to belong to T. interdigital by using PCR-RFLP and sequencing irrespective of the site of lesions. The predominance of zoophilic strains needs further investigation. Keywords: Dermatophytes; Trichophyton mentagrophytes; PCR-RFLP; Sequencing; Phenotypic features