Molecular epidemiology of trichophyton tonsurans isolated in Japan using RFLP analysis of non-transcribed spacer regions of ribosomal RNA genes.

Trichophyton tonsurans has been reported to be the causative agent of an epidemic of tinea corporis and tinea capitis among Japanese judoists and wrestlers. A molecular method using restriction enzyme analysis of PCR-amplified fragments targeting the non-transcribed spacer (NTS) region of ribosomal RNA genes in fungal nuclei was applied to a total of 232 strains of T. tonsurans isolated in Japan. Six molecular types, i.e., NTS types I, II, III, IV, V, and VI, were clearly detected in restriction analysis of fragments digested with MvaI and AvaI together. Of the 232 strains, 199 were classified as NTS I, 21 as NTS II, 7 as NTS III, 3 as NTS IV, 1 as type V, and 1 as type VI. Whereas the NTS I strains were found nationwide, most of the NTS II and NTS III strains were limited to central Japan. Of 164 strains isolated from judoists, 160 were classified as NTS I, which suggests that the majority of the cases were caused by a clonal lineage. On the other hand, the 48 strains isolated from wrestlers showed more variety, with 27 strains classified as NTS I, 17 as NTS II, and 4 as NTS III. We concluded that the epidemic was caused by at least three lineages of T. tonsurans. NTS VI strains, the major molecular type among sporadically isolated strains, were not observed among the epidemic strains, and strains of this type did not contribute to the present epidemic.