Virulence determinants, antifungal resistance, and genotype-phenotype associations in Candida bloodstream isolates: a three-year surveillance study from Northern India

Candidemia is increasingly driven by non-albicans multidrug-resistant Candida species, yet the relationship between virulence determinants and antifungal susceptibility remains incompletely understood. In this three-year surveillance study (2022-2025), 357 non-duplicate Candida bloodstream isolates from a tertiary care centre in northern India were analysed to characterize species distribution, extracellular virulence phenotypes, virulence-associated genes, and antifungal susceptibility profiles. Species identification was performed using phenotypic methods and confirmed by PCR-RFLP and MALDI-TOF MS, while antifungal susceptibility testing followed CLSI M27-A3 guidelines. Non-albicans Candida species predominated (76.8%), with Candida tropicalis as the most frequent isolate, followed by Candida albicans and Candidozyma auris. Multiplex PCR demonstrated a high prevalence of virulence-associated genes (HWP1, ALS1, SAP2, and PLB1), with concordance between gene detection and phenotypic expression of adhesion, biofilm formation, and extracellular enzyme activity. Echinocandins retained potent in vitro activity across species, whereas C. auris exhibited a multidrug-resistant phenotype, including high fluconazole resistance and reduced susceptibility to amphotericin B and caspofungin. Species-stratified analyses revealed significant positive correlations between esterase and hemolysin activity and amphotericin B minimum inhibitory concentrations in C. albicans and C. tropicalis (p < 0.01). Multivariate analysis identified elevated amphotericin B MICs and specific virulence traits as independent predictors of strong biofilm formation. These findings highlight species-specific associations among virulence expression, genetic determinants, and the antifungal response, supporting integrated surveillance approaches to improve the management of invasive candidiasis.