The opportunistic yeast pathogen Trichosporon asahii colonizes the skin of healthy individuals: analysis of 380 healthy individuals by age and gender using a nested polymerase chain reaction assay.

Deep-seated trichosporonosis is an opportunistic fungal infection with a poor prognosis and high mortality rate. The major causative agent is Trichosporon asahii; its route of infection is not clear. To elucidate whether this microorganism is part of the cutaneous microbiota, we examined skin samples from 380 healthy Japanese ranging in age from 0 to 82 years using a nested PCR assay. The colonization frequency of T. asahii increased with age up to 13-15 years in male and 30-39 years in female subjects, subsequently decreasing gradually in both sexes until senescence. Of the nine genotypes of the intergenic spacer region of the T. asahii rRNA gene, type 1 predominated (81.7%), followed by types 4 (6.7%) and 6 (5.5%). The distribution of identified genotypes was similar to that for T. asahii isolated from clinical specimens (blood and urine) of patients with deep-seated trichosporonosis and quite different from that of environmental isolates. Additionally, T. asahii DNA was detected stably from skin samples over 1 year. The opportunistic yeast pathogen T. asahii is part of the cutaneous fungal microbiota in humans. Cutaneous T. asahii may be one of the routes through which deep-seated trichosporonosis is acquired, whereas environmental T. asahii is not associated with this infection.