Identification and antifungal susceptibility profile of uncommon yeast species at Fattouma Bourguiba University Hospital in Tunisia

Abstract Despite the severe impact of uncommon yeast fungal infections and the pressing need for more research on the topic, there are still few studies available on the identification, epidemiology, and susceptibility profile of those pathogens. The aims of the current study were to define the profile of uncommon yeast species at Fattouma Bourguiba University Hospital using phenotypic, molecular, and proteomic methods and to study their antifungal susceptibility profile. Pre-identified uncommon yeast species were collected from 2018 to 2021. These isolates were further identified using phenotypic methods (ID32C® system and Vitek2® YST), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and sequencing. The antifungal susceptibility profile was studied using the reference CLSI broth microdilution method. In total, 30 strains were collected during the study period. Referring to the sequencing, the most isolated uncommon species were Saprochaete capitata, Candida lusitaniae, Candida kefyr, Candida inconspicua, and Candida guilliermondii. A total of 90% of isolates were correctly identified by MALDI-TOF MS compared to 76.7% and 63.3% by ID32® C and VITEK® 2 YST, respectively. The isolated species showed variable responses to antifungals. Candida guilliermondii showed increased azole minimum inhibitory concentrations. Misidentification of uncommon yeast species was common using commercial phenotypic methods. The high percentage of concordance of MALDI-TOF results with sequencing highlights its high performance and usefulness as a routine diagnosis tool.