Synergistic Effect And Mechanism Of Azoles And Fluoxetine Against Resistant Candida Albicans Attributed To Attenuating Fungal Virulence

Background:For the more and more widely using of wide-spectrum antibiotics, immunosuppressant, and medical implant device, the incidence of fungal infections has increased significantly in the last several years. The most commonly used drugs are the azoles, such as fluconazole (FLC), itraconazole (ITC) and voriconazole (VRC). The emerging drug-resistance becomes a major concern with regard to their clinical application. Since the development of any antifungal agents is far from easy, the drug’s combination turns out to be a practical way. SSRIs are being used as antidepressants and the first line therapy for premenstrual syndrome. The antifungal activity of selective serotonin-reuptake inhibitor (SSRIs) have been conducted. However, few were carried on to study its anti-biofilm activity and mechanism. So further study of the combination of azoles and SSRIs is of great significance for the problem of increasing drug-resistance of Candida species.Objectives:To evaluate the synergistic effects of selective serotonin reuptake inhibitor, fluoxetine combined with azoles against Candida albicans both in vitro and in vivo, and to explore its underlying mechanism.Methods:MICs, sMICs and time-kill curves were determined for resistant C. albicans. Galleria mellonella was used as a non-vertebral model in determining the efficacy of combined drugs against C. albicans in vivo. As to mechanism study, the gene expression of SAP gene family was determined by RT-PCR and extracellular phospholipase activities have been detected in vitro by egg yolk agar method.Results:The combinations resulted in synergistic activity against C. albicans strains, and an indifferent effect was found for the non-albicans Candida. For the biofilms formed over 4,8, and 12h, synergism was displayed by the combination of fluconazole/fluoxetine. In addition, the time-killing curves confirmed the synergism dynamically. G. mellonella studies agreed with in vitro analysis. In the aspect of mechanism study, we observed that fluconazole plus fluoxetine could cause a down-regulation of gene expression of SAP1-4 and weaken the activity of extracellular phospholipases of resistant C. albicansConclusions:The effect of azoles used in combination with fluoxetine was synergistic against resistant C. albicans, and it may diminish the virulence properties of C. albicans. Combination of fluoxetine and azoles may represent a brand-new approach of challenging the increasing of resistance of C. albicans and this study could provide deep insight into antifungal agent discovery and clinical therapy.