The effect of melatonin on antifungal susceptibility in planktonic and biofilm forms of Candida strains isolated from clinical samples.

In recent years, the significant increase in the isolation of antifungal resistant Candida species in presence of biofilm, have made it necessary to develop alternative agents for the treatment of these infections. In this study, the effect of antifungal susceptibility of melatonin were investigated in planktonic and biofilm forms of Candida strains isolated from the clinical samples sent to our laboratory. Biofilm formation was determined by modified microplate method. In order to determine antifungal susceptibility in biofilm-forming strains, MIC was determined by broth microdilution method in planktonic form, and MBEC values by Calgary biofilm method in biofilm form. Susceptibility tests were repeated in the presence of melatonin. Antifungal susceptibility tests repeated with antifungals combined with melatonin showed a decrease in both MIC and MBEC values; melatonin was found to be more effective especially in planktonic forms. While the most effective combination was achieved with fluconazole in the planktonic form, no statistically significant difference was found between the combinations in biofilm form. As a result, melatonin was thought to be a new alternative in the treatment of Candida infections.