Trichophyton tonsurans infection has been prevalent among individuals involved in contact sports in Japan since about 2000. The present review focuses on its diagnosis, molecular epidemiology, drug susceptibility, and infection control. The most commonly observed lesions of T. tonsurans, an anthropogenic dermatophyte, are tinea corporis and tinea capitis. However, the presence of asymptomatic carriers must be considered for infection control. Genotypic epidemiology using restriction fragment length polymorphisms (RFLP) in the non-transcribed spacer (NTS) region of the ribosomal RNA gene showed a lack of diversity of genotypes, and only the NTS I genotype is detected at present. In regard to drug susceptibility, terbinafine drug resistance has not been found to be associated with the RFLP genotypes, and it is assumed that there are no terbinafine-resistant strains in Japan. T. tonsurans coexisted with other fungi and bacteria in the scalp of asymptomatic carriers without affecting species diversity. T. tonsurans is an anthropogenic dermatophyte and may be difficult for the human immune system to eliminate. During an infection outbreak, screening of infection and treatment including asymptomatic carriers are essential to eradicate the infection.
The human body is host to a large number of commensal microbial species such as bacteria, fungi, and viruses. Among these, the human mycobiome is often neglected as a potential cause of disease, as it is thought to be comparatively much less abundant and less diverse than the human bacteriome. Additionally, most fungi are not easily cultured, even in specific media. Hence, their study has been limited to date, mainly because of the unavailability of methods used for their detection. However, the utilization of a novel metagenomic methodology will enable the identification of well-characterized mycobiomes in several parts of the human body and broaden our knowledge of their contribution to human health and disease. In this article, we review the role of the human mycobiome in the gut, respiratory organs, skin, genital tract, and carcinogenesis, highlighting the correlations between the human mycobiome and mycobiome-associated diseases.
Microsporum canis, a major causative agent of zoonotic dermatophytosis, has become prevalent in Japan. Molecular epidemiological surveys using multilocus microsatellite typing (MLMT), a sensitive genotyping tool for fungi, have been conducted to reveal intraspecies polymorphisms of M. canis. The present study utilized MLMT optimized for Japanese strains of M. canis to analyze epidemic trends of fungal infection. Six individual loci were targeted; namely, MS1, 2, 4, 5, 6, and 7. Analysis of data from 1974 through 2022 identified 416 strains, which were sorted into 60 genotypes by MLMT. The major genotypes showed changes in dominance during this period-changes that may reflect historical increases and decreases in the numbers of patients infected with M. canis patients. The main origins of infection included animal breeders and pet stores, as well as stray cat communities. Forty-nine episodes of familial outbreaks and cohabitant animal infections were recorded, and genotypes responsible for each episode were determined. MLMT analysis is not only a robust tool to understand population structures, but likely the most suitable method for tracking M. canis infections.
The patient was a 13-year-old boy who was a member of the judo club at his junior high school. Approximately 1 week prior to his presentation, he developed multiple erythematous pilaris papules on his occipital area and was treated by a local doctor. The erythematous lesions expanded to 10 × 10 cm, showing granulation with drainage and strong spontaneous pain. At this point, he visited our hospital. He was diagnosed with kerion celsi due to Trichophyton tonsurans by fungal examination. The patient was treated with terbinafine (125 mg/day) for 6 weeks, and a brush test at 6 weeks was negative. All 18 members of the judo club, including this patient, were investigated; brush tests were positive in 4 cases, and one was positive for tinea corporis alone. The patient’s family members parents were both negative. When an athlete is diagnosed with ringworm, T. tonsurans infection should be considered, and testing and treatment of family members and fellow athletes should be carried out to prevent the spread of infection.