Biocide, antifungal susceptibility and virulence characteristics of Clade 1 Candidozyma auris strains.

Abstract

Background: Candidozyma auris is an emerging multidrug-resistant fungal pathogen responsible for nosocomial outbreaks worldwide. In addition to antifungal resistance, its ability to persist in the hospital environment and tolerate commonly used biocides presents a critical challenge for infection control. However, the relationship between biocide tolerance, antifungal resistance, and virulence traits in C. auris remains poorly understood.

Methods: In this study, 47 C. auris Clade 1 isolates were evaluated using phenotypic and genotypic methods. ITS region sequencing was performed using Oxford Nanopore technology. Susceptibility testing was conducted for seven antifungal agents and four biocides using the CLSI reference microdilution method. Virulence factors including biofilm formation, secreted aspartyl proteinase, esterase, caseinase, phospholipase, and hemolysis were assessed.

Results: All isolates were identified as Clade 1. MIC values for antifungals ranged from 0.015 to 64 µg/mL, and for biocides from 0.0078 to 128 mg/L. Fluconazole resistance was found in 31% of isolates, while amphotericin B resistance was 4%; no echinocandin resistance was observed. Biofilm and SAP activity were detected in all isolates; esterase was positive in 87%, and caseinase in 4%. Statistically significant correlations were observed between amphotericin B and isavuconazole MICs (ρ = 0.32, p = 0.028), amphotericin B and triclosan MICs (ρ = 0.35, p = 0.018), and amphotericin B MICs and caseinase activity (ρ = 0.31, p = 0.035). These findings suggest potential phenotypic links between antifungal resistance and specific virulence traits.

Conclusions: This is the first study from Türkiye to evaluate the antifungal and biocide susceptibility alongside virulence characteristics of Clade 1 C. auris. While statistically significant associations were observed, we acknowledge that resistance mechanisms and pathogenicity pathways are distinct. Therefore, these correlations should be interpreted cautiously and warrant further investigation at the molecular level.