Intraspecies diversity of Trichosporon asahii as the causative agent of opportunistic fungal infection and summer-type hypersensitivity pneumonitis

Abstract

Trichosporon asahii is the major causative agent of the opportunistic infection trichosporonosis, and also causes summer-type hypersensitivity pneumonitis (SHP). Random amplification of polymorphic DNA analysis was used to determine the intraspecies diversity of T. asahii isolates from clinical specimens,the houses of SHP patients, and environmental material. Clinical isolates formed a cluster, characterized by a 90% matching coefficient, but they did not cluster with strains isolated from SHP patients houses or environmental sources. The biochemical characteristics of T. asahii isolates from the three sources were compared, and a phenogram was constructed. One of the two clusters included most of the clinical isolates and strains isolated from the houses, and the other cluster included most of the environmental isolates. There was a remarkable difference in the abilities of the strains belonging to these clusters to utilize several compounds. These results suggest that the genetic diversity and biochemical characteristics of T. asahii are related to the source of the isolates. In addition, based on the IGS1 sequence, which is located between the 26S and 5S rRNA genes, we identified five genotypes of T. asahii, which is a major causative agent of deep-seated trichosporonosis. Of the five genotypes, three were isolates that originated in Japan, whereas two were American isolates. IGS sequence analysis shows great potential as a new epidemiological tool.