Molecular identification, antifungal susceptibility, and resistance mechanisms of pathogenic yeasts from the China antifungal resistance surveillance trial (CARST-fungi) study.

To have a comprehensive understanding of epidemiology and antifungal susceptibilities in pathogenic yeasts, the China Antifungal Resistance Surveillance Trial (CARST-fungi) study was conducted. All yeast isolates were identified by ribosomal DNA sequencing. Antifungal susceptibilities were performed using CLSI M27-A4 broth microdilution method. Sequence and expression level of resistant-related genes in resistant/non-wide-type (NWT) isolates were analyzed. Totally 269 nonduplicate yeast isolates from 261 patients were collected. About half of the yeast isolates (127, 47.2%) were recovered from blood, followed by ascetic fluid (46, 17.1%). remained the most prevalent (120, 44.6%), followed by complex (50, 18.6%), (40, 14.9%), and (36, 13.4%). Fourteen (11.7%) isolates and 1 (2.0%) isolate were resistant/NWT to triazoles. Only 42.5% (17/40) were susceptible/WT to all the triazoles, with 19 (47.5%) isolates NWT to posaconazole and 8 (20%) cross-resistant to triazoles. Among , 20 (55.6%) and 8 (22.2%) isolates were resistant/NWT to voriconazole and posaconazole, respectively, and 4 (10.3%) isolates were cross-resistant to triazoles. Isavuconazole was the most active triazole against common isolates. Except for 2 isolates of cross-resistant to echinocandins which were also NWT to POS and defined as multidrug-resistant, echinocandins exhibit good activity against common species. All isolates were WT to AMB. For less common species, exhibited high MICs to echinocandins and FLC, and 1 isolate of showed high MICs to all the antifungals except AMB. Among triazole-resistant isolates, mutations were detected in 10/14 and 6/23 , while 21/23 showed overexpression. Overexpression of , , and exhibited in 14, 13, and 8 of 25 triazole-resistant isolates, with 5 isolates harboring mutations and 2 echinocandins-resistant isolates harboring S663P mutation in . Overall, the CARST-fungi study demonstrated that although remain the most predominant species, non- species accounted for a high proportion. Triazole-resistance is notable among and . Multidrug-resistant isolates of and less common yeast have been emerging.