Hemolytic Activity of Vaginal Candida albicans Isolates and Antifungal Effects of Quinalizarin with Hemolysis Modulation

This study evaluated the hemolytic activity of Candida albicans isolates from the female reproductive tract and investigated the in vitro effects of quinalizarin on fungal growth, hemolysis, and ECE1 expression. Ninety-four clinical C. albicans isolates and three ATCC reference strains were analyzed. Hemolytic activity was quantified in culture supernatants and normalized per 107 cells. Antifungal susceptibility and the effect of quinalizarin on hemolysis were assessed using broth microdilution and hemolysis assays. Expression of the ECE1 gene was evaluated by quantitative real-time PCR in three selected hemolytic strains. Drug interactions between quinalizarin and fluconazole were determined using the fractional inhibitory concentration index (FICI). Among the 97 tested strains, 78 exhibited hemolytic activity with variable intensity. Quinalizarin demonstrated antifungal activity, with MIC values ranging from 2 µg/mL to 256 µg/mL, and showed synergistic effects with fluconazole in selected strains. Exposure to quinalizarin at subinhibitory concentrations reduced ECE1 transcript levels to 22.8–73.6% of controls (p < 0.05) in the analyzed strains. However, the phenotypic effect on hemolysis was limited, with residual activity remaining high: 82% (p < 0.05), 93.7% (p < 0.05), and 83% (p < 0.05) relative to untreated controls in C. albicans ATCC 10231, ATCC 90028, and a clinical isolate, respectively. FICI analysis confirmed synergistic interactions between quinalizarin and fluconazole. This preliminary in vitro study highlights the need for further investigation into the relationship between ECE1 expression, candidalysin-mediated damage, and the antifungal potential of quinalizarin.