The antiparasitic drug Nitazoxanide enhances the susceptibility of Candida albicans to fluconazole

BACKGROUND: Fluconazole (FLC) is a widely used antifungal agent; however, Candida albicans is increasingly developing resistance to it. Given the limited range of available antifungal drugs, there is an immediate requirement for the development of novel approaches to improve FLC efficacy against resistant strains. METHODS: This study investigated the synergistic effects of nitazoxanide (NTZ) and FLC against FLC-resistant C. albicans. Combined antifungal activity was evaluated through in vitro and in vivo experiments, including broth microdilution assays, time-kill assays, and the Galleria mellonella infection model. To explore potential mechanisms, hyphal growth inhibition, intracellular adenosine triphosphate (ATP) levels, reactive oxygen species (ROS) production, expression of resistance-related genes, Rhodamine 6G (Rh6G) efflux, and membrane potential changes were assessed. RESULTS: NTZ combined with FLC exerted a synergistic antifungal effect against FLC-resistant C. albicans. The combination increased ROS production, decreased ATP levels and metabolic capacity, inhibited hyphal growth of C. albicans and biofilm formation, suppressed efflux gene expression, lowered membrane potential, and reduced drug efflux, among others. Moreover, it was confirmed that FLC combined with NTZ not only effectively enhanced the survival rate of G. mellonella infected with C. albicans, but also significantly reduced the colony burden in G. mellonella. CONCLUSIONS: The results in this study provide preliminary experimental evidence supporting the potential clinical application of NTZ combined with FLC. This regimen may improve FLC efficacy and represents an exploratory approach for optimizing antifungal treatment strategies.