Trichosporon asahii, which is distributed in the environment, is the major causative agent of the opportunistic infection trichosporonosis, and it also causes summer-type hypersensitivity pneumonitis (SHP). Random amplification of polymorphic DNA analysis was used to determine the intraspecies diversity of 39 T. asahii isolates from clinical specimens, SHP patients' houses, and environmental materials. The three primers used revealed 46 polymorphic bands. A phenogram was generated by the unweighted pair-group method with arithmetic mean. 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. In addition, the biochemical characteristics of 86 strains from three sources were examined with 31 compounds using an ID32C kit, and a phenogram was constructed. The phenogram consisted of three major clusters. Cluster I included most of the clinical SHP isolates, and cluster II included most of the environmental isolates. Cluster III contained only one strain. A remarkable difference was found in the abilities of the strains belonging to clusters I and II to utilize six compounds. These results suggest that the genetic diversity and biochemical characteristics of T. asahii seem to be related to the source of the isolate. We also found a specific DNA fragment for the clinical isolates and strains isolated from SHP patients' houses.

The fungus Trichosporon asahii is distributed widely in the environment and is frequently isolated from clinical specimens. It can cause life-threatening disseminated infections, including breakthrough infection after the administration of candin antifungal drugs. However, the definitive infection route is still unclear. In this study, 43 T. asahii genotypes were detected in 72 fecal samples from healthy subjects. The rRNA genotypes of the species were determined using a culture-independent method. The genotypes of T. asahii were almost identical to those of reported clinical isolates. Therefore, T. asahii colonizing the gastrointestinal tract might be associated with the development of trichosporonosis, and not environmental isolates.