Susceptibility Patterns and Molecular Identification of TrichosporonSpecies

ABSTRACTThe physiological patterns, the sequence polymorphisms of the internal transcriber spacer (ITS), and intergenic spacer regions (IGS) of the rRNA genes and the antifungal susceptibility profile were evaluated for their ability to identify Trichosporonspp. and their specificity for the identification of 49 clinical isolates of Trichosporonspp. Morphological and biochemical methodologies were unable to differentiate among the Trichosporonspecies. ITS sequencing was also unable to differentiate several species. However, IGS1 sequencing unambiguously identified all Trichosporonisolates. Following the results of DNA-based identification, Trichosporon asahiiwas the species most frequently isolated from deep sites (15 of 25 strains; 60%). In the main, other Trichosporonspecies were recovered from cutaneous samples. The majority of T. asahii, T. faecale, and T. coremiiformeclinical isolates exhibited resistance in vitro to amphotericin B, with geometric mean (GM) MICs >4 μg/ml. The other species of Trichosporondid not show high MICs of amphotericin B, and GM MICs were <1 μg/ml. Azole agents were active in vitro against the majority of clinical strains. The most potent compound in vitro was voriconazole, with a GM MIC ≤0.14 μg/ml. The sequencing of IGS correctly identified Trichosporonisolates; however, this technique is not available in many clinical laboratories, and strains should be dispatched to reference centers where these complex methods are available. Therefore, it seems to be more practical to perform antifungal susceptibility testing of all isolates belonging to Trichosporonspp., since correct identification could take several weeks, delaying the indication of an antifungal agent which exhibits activity against the infectious strain.