inhibitory effect of fluconazole combined with amphotericin b on fluconazole-resistant candida albicans biofilm formation

Background objective: the incidence of biofilmrelated infections caused by candida albicans has increased dramatically. c. albicans biofilmrelated infections are more resistant to antifungal medications. this work was an attempt to examine inhibitory effects of fluconazole in combination with amphotericin b on fluconazoleresistant c. albicans biofilm. materials methods: fluconazoleresistant c. albicans was identified among colonized clinical isolates of c. albicans obtained from the patients at shahid beheshti hospital, yasooj, iran, between september 2016 and january 2017. the mics of fluconazole alone and in combination with amphotericin b were determined on fluconazoleresistant c. albicans by broth microdilution method based on the clsi document m27a3 and the synergistic effects were interpreted by the fic index. to address the inhibitory effects of drug combinations, we investigated the antibiofilm activities of fluconazole alone and in combination with amphotericin b against fluconazoleresistant c. albicans using crystal violet staining, light field microscopy and expression analysis of hwp1 using rtpcr. results: ten percent of the colonizing clinical isolates of c. albicans were found to be fluconazoleresistant. the fluconazole combined with amphotericin b exhibited synergistic and partial synergistic effects against fluconazoleresistant c. albicans isolates with fic index ranging from 0.50 to 0.75. our findings demonstrated that fluconazole combined with amphotericin b exerted a significant reduction and inhibition on biomass, biofilm formation and the expression levels of hwp1 (p<0.05).conclusion: fluconazole combined with amphotericin b showed potent inhibitory activity against fluconazoleresistant c. albicans biofilm formation. other measures are important to determine the effectiveness of the drug combinations against c. albicans biofilm.