Synergistic antibacterial and antibiofilm efficacy of nisin in combination with p-coumaric acid against food-borne bacteria Bacillus cereus and Salmonella typhimurium

The aim of the study was to evaluate possible antibacterial and antibiofilm efficacy of a bacteriocin, nisin with two essential oil components linalool and p-coumaric acid in combination against food-borne bacteria Bacillus cereus and Salmonella typhimurium. Their inhibition effects on planktonic cells and preformed biofilms were evaluated using microbroth dilution and checkerboard titration methods. Nisin/p-coumaric acid combination showed synergistic effects against planktonic cells of both the studied bacteria, whereas nisin/linalool combination showed synergistic activity against B. cereus and additive effect against S. typhimurium. In preformed biofilms, nisin by itself failed to show > 50% antibiofilm efficacy against both the studied bacteria, but in combination with linalool and p-coumaric acid, it exerted > 50% antibiofilm efficacy. On the basis of fractional inhibitory concentration indices values, nisin/p-coumaric acid combination exhibited synergistic antibiofilm activity, whereas nisin/linalool combination showed additive effects against preformed biofilms of studied bacteria. The results provide evidence that p-coumaric acid due to its synergistic interactions with nisin against planktonic cells and biofilms of both Gram-positive and Gram-negative food-borne bacteria enhanced the antibacterial spectrum of nisin, which subsequently may facilitate their use in the food industry.