Voriconazole Activity Against Pichia kudriavzevii: Influence of Glucose Availability and Culture Medium on Growth, Biofilm Formation, and Antifungal Susceptibility

Invasive candidiasis remains a major cause of morbidity and mortality worldwide, with increasing relevance of non-Candida albicans species, particularly Pichia kudriavzevii, which is associated with high mortality and intrinsic resistance to fluconazole. This study evaluated the effect of voriconazole (VRC) on P. kudriavzevii growth, biofilm formation, and metabolic activity under different nutritional conditions. Planktonic growth and biofilm development were analyzed in Sabouraud dextrose broth (SDB), RPMI-1640, and RPMI-1640 supplemented with glucose (20 g·L−1). Antifungal activity was assessed by optical density (OD570) and XTT reduction assays, and biofilm morphology was examined by light microscopy. Glucose consumption was also determined during growth. VRC showed dose-dependent inhibition in SDB, reducing growth and biofilm metabolic activity by up to 94% and 98%, respectively. In contrast, in RPMI-1640, inhibition was significantly lower (≤27% growth and ≤77% biofilm reduction). Glucose supplementation partially restored antifungal susceptibility and increased biofilm metabolic activity. Growth kinetics confirmed VRC-induced delays in proliferation and impaired glucose utilization. These results demonstrate that VRC activity against P. kudriavzevii is strongly dependent on environmental nutrient availability, particularly glucose, which modulates fungal metabolism, biofilm development, and antifungal susceptibility, highlighting the importance of standardized antifungal susceptibility testing conditions and the role of metabolic state in azole efficacy.