Molecular epidemiology of a major subgroup of Arthroderma benhamiae isolated in Japan by restriction fragment length polymorphism analysis of the non-transcribed spacer region of ribosomal RNA gene.

Arthroderma benhamiae vectored by small animals, such as household pets, causes tinea lesions on human skin. The number of tinea cases caused by this species is increasing in Japan. We attempted to develop a simple molecular method for strain discrimination, which is expected to be useful in molecular epidemiology. Out of the 61 strains of A. benhamiae registered at our institute, 46 A. benhamiae strains showed very high degrees of sequence similarity on cluster analysis of the internal transcribed spacer regions of ribosomal RNA (rRNA) genes. These 46 strains, including 22 strains isolated from Japan, were further used for strain typing by analyzing the non-transcribed spacer (NTS) region of the rRNA gene. Polymerase chain reaction was performed using a primer pair designed for amplification of a part of the NTS region, and the amplicons were successfully discriminated by restriction fragment length polymorphism (RFLP) analysis performed using MvaI. RFLP analysis showed 11 NTS types (NTS1-NTS11) among the 46 strains. Out of the 22 Japanese strains, 10 were of the NTS8 type; 6, of the NTS1 type; 3, of the NTS2 type; and 3, of the NTS5 type. Molecular typing showed consistency of NTS types among the strains isolated from different lesions on the same patient, among the strains derived from the same family, and among the strains from pets and their owners. We observed that 3 out of the 4 NTS types among the Japanese strains were detected outside Japan as well.