Lactobacillus casei and its byproducts alter the virulence factors of foodborne bacterial pathogens

• L. casei and its byproduct could inhibit growth of foodborne bacterial pathogens.
• L. casei could reduce adherence and invasion abilities of foodborne pathogens.
• Byproducts of L. casei could alter virulent gene expression of foodborne pathogens.
• With prebiotic-like effect, cocoa enhanced the antimicrobial effects of L. casei.

Introduction of prebiotics and probiotics as daily food supplements is believed to be a promising way of controlling enteric or other chronic infections and improving gut health. In this study, the effects of Lactobacillus casei on growth and virulence properties of foodborne enteric bacterial pathogens enterohemorrhagic Escherichia coli EDL933, Salmonella Typhimurium LT2, and Listeria monocytogenes LM2 were investigated. Mixed culture of L. casei with each of these pathogens showed that L. casei could competitively exclude or inhibit the growth of pathogens by >99% within 48 h. Further investigation revealed that the antimicrobial byproducts produced by L. casei in cocoa pre-treated cultural supernatant significantly reduced the growth, increased the hydrophobicity values, blocked the interaction with human intestinal epithelial cell (INT-407), and altered the virulence genes expression of these bacterial pathogens. These results suggest the possibility of applying L. casei with cocoa in preventing/reducing foodborne pathogen infections in gut environment.