Three-locus identification, genotyping, and antifungal susceptibilities of medically important Trichosporon species from China

Abstract

Three reference and 45 clinical isolates of Trichosporon were analyzed by conventional phenotypic and molecular methods to determine the species and genotypes of Trichosporon isolates from China. Target loci for molecular methods included the internal transcribed spacer (ITS) region, the D1/D2 domain of the 26S rRNA gene, and the intergenic spacer 1 (IGS1) region. Identification of eight Trichosporon species was achieved, of which Trichosporon asahii was the most common. Of the sequence-based molecular methods, the one targeting the D1/D2 domain assigned 97.9% (47/48) of isolates (seven species) correctly, while tests targeting both the ITS and IGS1 regions correctly identified all 48 isolates. The commercial API 20C AUX and Vitek 2 Compact YST systems correctly identified 91.9% and 73% of isolates when their biochemical profiles were queried against those of species contained in the databases, respectively, and misidentified 63.6% and 36.4% of isolates of species that were unclaimed by the databases, respectively. The predominant genotype among T. asahii clinical isolates, genotype 4 (51.4%), is rarely found in other countries. Voriconazole and itraconazole were the most active drugs in vitro against all the Trichosporon species tested, while caspofungin and amphotericin B demonstrated poor activity.

Fig. 1.

MPTs by comparison of sequences of the IGS1 region and the ITS region plus D1/D2 domain of the 26S rRNA gene. ITS region, D1/D2 domain, and IGS1 region sequences from the whole-genome sequence of Cryptococcus neoformans var. neoformans strain B-3501A were used as outgroups. Eight Trichosporon species identified in the present study are indicated; and four T. asahii IGS1 genotypes are marked in the IGS1 MPT (left tree) as well. Scale bars indicate branch lengths corresponding to 5 nucleotide changes for the IGS1 region (bottom left) and 10 nucleotide changes for the ITS region plus D1/D2 domain (bottom right).