Effectiveness of Nisin Synergize With Licochalcone A For Inhibiting Listeria Monocytogenes  Biofilms

Abstract

Listeria monocytogenes is a common foodborne pathogen capable of developing biofilms, leading to food contamination and spoilage. Numerous combined antibacterial strategies based on Nisin in combination with various plant extracts or their components have been developed against L. monocytogenes. The combined antibacterial and antibiofilm efficacy of Nisin and Licochalcone A (LCA) against L. monocytogenes ATCC 19114 and CMCC 8605 was investigated in this research. The synergy between Nisin and LCA against L. monocytogenes was evidenced, with fractional inhibitory concentration indices (FICI) values of 0.375 for the two L. monocytogenes strains. The growth and viability of L. monocytogenes ATCC 19114 and CMCC 8605 were inhibited by the combined treatment. Meanwhile, the combined treatment successfully inhibited biofilm formation and eradicated existing biofilms, as verified through crystal violet staining. Furthermore, scanning electron microscopy and confocal scanning laser microscopy enabled visualization of the destruction of established L. monocytogenes biofilms by Nisin and LCA individually or combined. The cell viability of biofilms, biofilm metabolic activity, and EPS production of the L. monocytogenes biofilm were significantly decreased by the combined treatment (P < 0.05). Moreover, the findings indicated that the expression levels of genes linked to flagella, quorum sensing, EPS production and virulence factors were regulated through the combined application of Nisin and LCA. The study also showed that Nisin + LCA reduced L. monocytogenes biofilm on the cantaloupe peel surface. To summarize, the combination of Nisin and LCA demonstrated great potential for reducing and controlling the L. monocytogenes contamination within the food industry.

Keywords: Nisin, Licochalcone A, Synergistic effect, L. monocytogenes, Antibacterial, Antibiofilm