Global emergence of novel genotypes and antifungal resistance in Trichosporon asahii revealed by IGS1 rDNA revision

Trichosporon asahii is a basidiomycetous yeast-like fungus that emerged as the main cause of invasive trichosporonosis, exhibiting high mortality rates. Species and genotype identification rely on sequencing of the IGS1 rDNA. By examining sequences in public genomic repositories and compiling epidemiological and antifungal data from the literature, we investigated the emergence of novel genotypes (G) and their relation to antifungal resistance. We analyzed 916 sequences from 892 isolates collected from 1911 to 2024. Genotypic analysis confirmed 14 reference genotypes and described 25 novel genotypes. Geographic distribution revealed a ubiquitous presence of T. asahii in 19 territories and the prevalence of G1 worldwide. Most sequences originated from blood and urine isolates, with the prevalence of G1 in all sampled sites, G4 in respiratory isolates, and G7 in urine. Minimal inhibitory concentration analyses showed G3 and G7 with the highest geometric mean (GM) values for voriconazole (VRC), while G4 presented the highest for posaconazole (POS). Non–wild-type isolates appeared across major genotypes. Bloodstream isolates showed higher GM values and more non-wild-type isolates for fluconazole and VRC, whereas urine isolates exhibited elevated GM values for VRC and POS. Overall, our findings reveal expanded IGS1 diversity and associate G3, G4, and G7 to reduced triazole susceptibility, highlighting the need for genotype-based surveillance.