Change in dominant genotype of Microsporum canis, a causative fungus of zoonotic dermatophytosis, in Japan over the past 40 years.

Multilocus microsatellite typing was performed on 124 strains of Microsporum canis, which is the most prevalent causative fungus of zoonotic dermatophytosis, isolated in Japan between 1974 and 1981. The strains had been enclosed in glass ampoules by freeze dried process. Genotypes were detected by capillary electrophoresis targeted on six microsatellite regions, and 19 genotypes were found among these 124 strains. The most frequent genotype, which had been reported as genotype L in a previous study, comprised 56 of the 124 strains (45.2%), although genotype L was reported to comprise only six of 165 strains (3.6%) isolated between 2010 and 2017. A decrease in the prevalence of genotype L may have led to the retreat of M. canis infection in 1996 to 2006. On the other hand, genotype A, the second most predominant genotype in the aforementioned studies of strains isolated between 2010 and 2017, comprised just four of 124 strains (3.2%) in the present study. Thus, these studies reveal that prevalences of some major genotypes have changed over the last 40 years. Genotype consistency of strains was proven in all of 12 familial cases, each of which was infected with a single genotype. We emphasize the importance of fungal culture collection for further studies with new techniques in the future.