Enhancement of the Antibiofilm Activity of Nisin against Listeria monocytogenes Using Food Plant Extracts

Listeria monocytogenes is a foodborne pathogen exhibiting a high mortality rate. In addition to the robust tolerance to environmental stress, the ability of L. monocytogenes to develop biofilms increases the risk of contaminating food processing facilities and ultimately foods. This study aims to develop a synergistic approach to better control Listeria biofilms using nisin, the only bacteriocin approved as a food preservative, in combination with gallic-acid-rich food plant extracts. Biofilm assays in the presence of nisin and gallic acid or its derivatives revealed that gallic acid significantly decreased the level of biofilm formation in L. monocytogenes, whereas ethyl gallate, propyl gallate, and lauryl gallate enhanced biofilm production. As gallic acid is widely distributed in plants, we examined whether extracts from gallic-acid-rich food plants, such as clove, chestnut, oregano, and sage, may generate similar antibiofilm effects. Remarkably, sage extracts enhanced the antibiofilm activity of nisin against L. monocytogenes; however, the other tested extracts increased biofilm formation, particularly at high concentrations. Moreover, sage extracts and nisin combinations significantly reduced the biofilm formation of L. monocytogenes on stainless steel. Sage is a common food spice and has various beneficial health effects, including antioxidation and anti-cancer properties. The findings in this study demonstrate that sage extracts can be potentially combined with nisin to prevent biofilm production in L. monocytogenes.