Synergistic antimicrobial activity of Vitamin C with Selenium compounds against Gram-positive bacteria.

Abstract

Antibiotics have been a boon to the world to treat bacterial infections. But the overuse and inappropriate utilization of these medications is greatly contributing to the development of antibiotic resistance in the bacteria. Thus, there have been constant attempts to develop antibiotic alternatives which are safer for human consumption and food application. The use of various natural products like Vitamins, terpenes, herbs, etc. can be a potential alternative strategy to combat the resistant bacteria. Here, the antibacterial potential of selenium-based compounds (sodium selenite, ebselen), Vitamin C, and essential oil Thymol has been explored against common food borne pathogens E coli and Staphylococcus aureus. Selenium based compounds (Ebselen and sodium selenite) interfere with the activity of antioxidant enzyme system in the bacteria and thus act as antibacterial. Essential oils act on the integrity of cell membrane that changes the membrane permeability that can have detrimental influence on the cell metabolism and can ultimately lead to cell death. Vitamin C exerts its pro-oxidant activity and enhance the ROS production, thus acting as antibacterial. Microdilution assays have been performed to determine the minimum inhibitory concentrations (MIC) of the used compounds against the bacteria. Then, checkerboard assay was used to determine the effects of interaction of different compounds when used in combination. Individually when these compounds are used, their higher concentration is required for inhibiting or killing the bacteria, which can be toxic when consumed by humans. While, when such compounds are used in combination, they can exert synergistic effect against pathogens at a very low concentration, comparatively safer for human consumption. Moreover, the compounds used at such low concentrations do not even alter the organoleptic properties of the food on which these are applied. In this study, among all the combinatorial interactions, Vitamin C and Sodium Selenite showed potential synergistic interaction against S aureus where the MIC value of Vitamin C and Sodium selenite were reduced by 16 folds and 32 folds respectively.