Antimicrobial activity of a mixture of surfactants produced by Acinetobacter calcoaceticus IMV B-7241 with antifungal drugs and essential oils

Abstract

Introduction. The aim of the work was to study the effect of a mixture of surfactants synthesized by Acinetobacter calcoaceticus IMV B-7241 under various cultivation conditions with antifungal drugs (clotrimazole and fluconazole) and essential oils (cinnamon and lemongrass) on yeast of genus Candida. Material and methods. The cultivation of A. calcoaceticus IMV B-7241 was carried out in a basic medium that did not contain NaCl (medium 1), contained NaCl, 2.0 g/l (medium 2), contained NaCl, 2.0 g/l, and KCl, 1.0 g/l (medium 3). The surfactants were extracted from supernatant of cultural liquid by modified Folch mixture. Antimicrobial properties of the surfactants, antifungal drugs and essential oils were determined by index of the minimum inhibitory concentration (MIC). To assess the synergistic effect of a mixture of surfactants with antifungal drugs or essential oils the fractional inhibitory concentration index was used. Results and discussion. Surfactants synthesized by A. calcoaceticus IMV B-7241 on the basic medium were the most effective antimicrobial agents against the yeasts strains Candida albicans D-6, C. tropicalis RE-2 and C. utilis BVS-65 with MIC 22.5–45 μg/ml that were 2.6–17 times lower than the values determined for surfactants synthesized on modified media. At the same time, regardless of the strain cultivation in different media, all surfactants showed synergism of antifungal activity with clotrimazole, fluconazole, cinnamon or lemongrass essential oils. Thus, in the presence of surfactants synthesized on basic and modified media in a mixture with antifungal drugs, MIC of clotrimazole and fluconazole against the studied yeast test cultures decreased by 4–32 times. The use of a mixture of essential oils with surfactants synthesized by A. calcoaceticus IMV B-7241 growing in different media made it possible to reduce MIC of cinnamon and lemongrass oils against yeasts of Candida genus 4–18 and 8–32 times, respectively. At the same time, the index of fractional inhibitory concentration did not exceed 0.5, which indicates the synergism of anifungal activity between the studied compounds. Conclusion. The results confirm the possibility to reduce the minimum inhibitory concentrations of antifungal drugs or essential oils against members of genus Candida by their mixture with microbial surfactants.