Genotypic Analysis of Candida tropicalis Clinical Isolates From Korea via Multilocus Sequence Typing

Candida tropicalis is a clinically significant non-albicans species that has shown increasing azole resistance globally. Despite its growing clinical importance, genotypic and epidemiological data from East Asia, particularly Korea, remain limited. This study aimed to expand the global understanding of C. tropicalis population structure by genotyping clinical isolates from Korea and identifying novel sequence types. Thirty-four clinical isolates collected from tertiary hospitals across Korea between 2012 and 2019 were analyzed using multilocus sequence typing (MLST) based on six housekeeping genes (ICL1, MDR1, SAPT2, SAPT4, XYR1, and ZWF1). A total of 21 diploid sequence types (DSTs) were identified, including three novel DSTs (1418, 1419, and 1420) not previously recorded in the MLST central database. Notably, DST844 (CTR-19 isolate) exhibited elevated minimum inhibitory concentration (MIC) to fluconazole, suggesting a potential novel resistance phenotype. Phylogenetic and goeBURST analyses revealed 11 distinct clonal complexes (CCs), some of which showed similarity to Chinese and Brazilian lineages, indicating cross-regional evolutionary links. These findings enhance the global MLST data set, provide new insights into the molecular epidemiology of C. tropicalis in Korea, and highlight the need for continued antifungal resistance surveillance, particularly for emerging DSTs.