Reversal of Azole Resistance in Candida albicans by Sulfa Antibacterial Drugs

Invasive candidiasis presents an emerging global public health challenge due to the emergence of resistance to the frontline treatment options, such as fluconazole. Hence, the identification of other compounds capable of pairing with fluconazole and averting azole resistance would potentially prolong the clinical utility of this important group. In an effort to repurpose drugs in the field of antifungal drug discovery, we explored sulfa antibacterial drugs for the purpose of reversing azole resistance inCandida . In this study, we assembled and investigated a library of 21 sulfa antibacterial drugs for their ability to restore fluconazole sensitivity inCandida albicans . Surprisingly, the majority of assayed sulfa drugs (15 of 21) were found to exhibit synergistic relationships with fluconazole by checkerboard assay with fractional inhibitory concentration index (ΣFIC) values ranging from <0.0312 to 0.25. Remarkably, five sulfa drugs were able to reverse azole resistance in a clinically achievable range. The structure-activity relationships (SARs) of the amino benzene sulfonamide scaffold as antifungal agents were studied. We also identified the possible mechanism of the synergistic interaction of sulfa antibacterial drugs with azole antifungal drugs. Furthermore, the ability of sulfa antibacterial drugs to inhibitCandida biofilm by 40%in vitro was confirmed. In addition, the effects of sulfa-fluconazole combinations onCandida growth kinetics and efflux machinery were explored. Finally, using aCaenorhabditis elegans infection model, we demonstrated that the sulfa-fluconazole combination does possess potent antifungal activityin vivo , reducingCandida in infected worms by ∼50% compared to the control.