Catechin Augments the Antifungal Efficacy of Fluconazole Against Candida parapsilosis

The rising global incidence of <i>Candida parapsilosis</i> infections is increasingly complicated by antifungal resistance, resulting in frequent therapeutic failure. This study investigated the potential of the natural compound catechin to enhance the efficacy of fluconazole through synergistic interaction. We evaluated the susceptibility of <i>C. parapsilosis</i> clinical isolates and a reference strain to combinations of catechin and fluconazole using standardized microbiological assays and molecular techniques. In vivo efficacy was assessed using the <i>Galleria mellonella</i> infection model. Mechanistic studies included the measurement of intracellular reactive oxygen species (ROS) production and plasma membrane permeability. Catechin alone caused growth retardation in all strains. However, the combination of catechin and fluconazole resulted in complete growth inhibition of the reference strain and significant growth reduction in azole-resistant clinical isolates. While the combination slightly increased intracellular ROS production, no significant changes in plasma membrane permeability or membrane potential were observed. Notably, catechin induced the expression of the resistance-associated genes <i>CpTAC1</i> and <i>CpCDR1B</i> in resistant isolates. In vivo experiments demonstrated that catechin significantly reduced mortality in <i>G. mellonella</i> larvae infected with <i>C. parapsilosis</i>. These findings suggest that catechin is a promising candidate for developing synergistic antifungal therapies against resistant <i>Candida</i> species.