Antibiofilm effect of nisin alone and combined with food-grade oil components (thymol and eugenol) against Listeria monocytogenes cocktail culture on food and food-contact surfaces

Listeria monocytogenes is a prominent foodborne pathogen with potent biofilm-forming capability, which is to be crucial for its antimicrobial resistance and persistence. Therefore, using a combination of preservative components (hurdle technology) to control biofilms is a promising strategy. The purpose of this study was to investigate the antibiofilm efficacy of nisin alone and combined with thymol and eugenol against L. monocytogenes cocktail biofilm formed on abiotic (rubber and MBEC™ biofilm device) and biotic (lettuce) surfaces. Results showed that nisin at low concentrations (250 and 500 IU/mL) was not able to inhibit the biofilms to an acceptable level. Sub-MICs (0.5 × MIC) of thymol (0.02%) and eugenol (0.075%) did not significantly inhibit (P > 0.05), but at high concentration (2 × MIC) inhibited significantly (P < 0.05). When nisin (250 or 500 IU/mL) was combined with thymol at 0.5 × MIC (0.02%), 1 × MIC (0.04%), and 2 × MIC (0.08%) or eugenol at 0.5 × MIC (0.075%), 1 × MIC (0.15%), and 2 × MIC (0.30%), the inhibitory effect was remarkably superior to that of the single compounds. These results suggest the feasible benefits of combining nisin with food-grade essential oil components to inhibit L. monocytogenes biofilm formation in the food industry.