Comparative Analysis of Virulence Traits and Fluconazole-Response Mechanisms in Clinical Isolates of Candidozyma auris

Candidozyma auris (formerly known as Candida auris) has emerged as a formidable clinical fungal pathogen as a result of its multidrug resistance and persistent colonization capabilities. In this study, three clinical C. auris strains (namely C. auris strain 01, C. auris strain 03, and C. auris strain 13) with distinct origins were characterized to investigate their phenotypic variations and mechanisms of azole resistance. Comprehensive profiling revealed significant inter-strain differences in biofilm formation, cell surface hydrophobicity, adhesion capacity, and phospholipase activity. Testing for antifungal susceptibility showed that the three clinical strains exhibited different minimum inhibitory concentrations for multiple azoles (fluconazole, voriconazole, and itraconazole) and echinocandins (anidulafungin and micafungin). Sequencing identified Y132F mutations in the ERG11 gene of the three clinical strains. Mechanistic investigations demonstrated that fluconazole exposure significantly upregulated the expression of efflux pump genes (CDR1 and CDR2) and the genes encoding their transcriptional regulators (MDR1 and TAC1b). In a murine skin colonization model, comparing data from the standard strain C. auris strain CBS12766 and clinical strains of C. auris strain 03 and C. auris strain 13 exhibited a significantly higher fungal burden of tissue, whereas strain C. auris strain 01 showed an intermediate level. Host immunity response analysis revealed that expression of the IL-1β gene was significantly elevated in C. auris strain CBS12766-infected mice, while expression of IL-6 and CXCL-1 genes was predominantly increased in the C. auris strain 01, with TNF-α gene expression levels being comparable across all strains. Histopathological examination confirmed local infiltration of inflammatory cells and mild epidermal edema, indicating active host immune engagement. Overall, our findings highlighted substantial phenotypic heterogeneity, different colonization capacities, and differences in expression of inflammatory cytokines among the C. auris strains. Further investigations into fluconazole-response mechanisms identified enhanced efflux pump activity, along with ERG11 gene Y132F mutations and transcription factor modulation among these clinical strains.