The effect of melatonin to antifungal susceptibility in planktonic and biofilm forms of candida strains which isolated from clinical samples

In recent years, significant increase in the isolation of the antifungal resistant Candida species in the presence of biofilm has made it mandatory to develop alternative agent for the treatment of these infections. In this study the effect of melatonin to antifungal susceptibility in planktonic and biofilm forms of Candida strains which isolated from clinical samples that sent to Duzce University, Faculty of Medicine, Department of Medical Microbiology was investigated. The identification of the strains made with germ tube test, cornmeal-Tween 80 agar morphological assessment and automated system. Biofilm formation was investigated with modified microplate method. MIC and MBEC values were detected with broth microdilution method for planktonic form and Calgary biofilm method for biofilm form, respectively to determine antifungal susceptibility of strains which biofilm formation was observed. Susceptibility tests were repeated in the presence of melatonin. The species distribution of the 350 strains which included in the study 64,8% C. albicans, 15,7% C. glabrata, 8,6% C. tropicalis, 5,4% C. parapsilosis, 5,5% other species (C. kefyr, C. guilliermondii, C. dubliniensis, C. krusei, C. lusitaniae) were determined. Biofilm formation was observed in 9.7% of the strains. Considering the species level biofilm formation reported in C. albicans was 2,6% while Non-albicans Candida species was 22,7% . All strains which investigated antifungal susceptibility in planktonic form were susceptible to amphotericin B. One of the C. tropicalis strains was susceptible-dose dependent to fluconazole, one C. albicans strain was susceptible-dose dependent to voriconazole and resistance to caspofungin, one each C. tropicalis and C. kefyr strains were resistance to caspofungin. All strains which investigated antifungal susceptibility in biofilm form were resistance to amphotericin B. Three of the strains (C. albicans, C. parapsilosis, C. guilliermondii) were susceptible to fluconazole while other strains were resistance. Only C. guilliermondii was susceptible to voriconazole while others were resistance. All of the strains were resistance to caspofungin. According to the repeated antifungal susceptibility tests presence of melatonin, both MİC and MBEC values were decreased. In planktonic form, resistance or susceptible-dose dependent strains became susceptible while in biofilm form even if MBEC values were decreased, strains resistance profile was not changed. Consequently, the result of the combination of melatonin with antifungal agents decline in the value of MIC and MBEC suggests that melatonin is a new alternative in the treatment of Candida infections. Key Words: Antifungal susceptibility, biofilm, Candida, melatonin.