Extracellular vesicles from Lactiplantibacillus plantarum inhibit the biofilm formation of Listeria monocytogenes and reduce bacterial contamination on romaine lettuce

Biofilms formed by foodborne pathogens such as Listeria monocytogenes pose a serious risk to food safety. Probiotics and their derivatives have been widely explored as alternatives to conventional antimicrobial strategies for biofilm control. In this study, extracellular vesicles (EVs) were isolated from Lactiplantibacillus plantarum (LpEVs) and characterized, and their antibiofilm activity against L. monocytogenes was investigated. Their inhibitory effects on L. monocytogenes biofilm were evaluated using romaine lettuce as a food model. Results showed that LpEV treatment significantly reduced biofilm formation without affecting bacterial survival. LpEVs suppressed the expression of luxS and the production of autoinducer-2, thereby interfering with quorum sensing (QS) in L. monocytogenes. LpEVs downregulated QS-related genes associated with motility, adhesion, and virulence. They also impaired not only bacterial swimming motility but also adhesion to and invasion of intestinal epithelial cells. The surface application of LpEVs on romaine lettuce leaves markedly reduced L. monocytogenes biofilm formation and bacterial contamination without compromising visual sensory quality. Therefore, LpEVs could be used as natural antimicrobial agents that interfere with QS-mediated biofilm formation by L. monocytogenes and could also be effectively applied to enhance the microbial safety of fresh produce.