Lactobacillus casei expressing Internalins A and B reduces Listeria monocytogenes interaction with Caco‐2 cells in vitro

Summary Listeria monocytogenes has been implicated in a number of outbreaks including the recent largest outbreak in South Africa. Current methods for prevention of foodborne L. monocytogenes infection are inadequate, thus raising a need for an alternative strategy. Probiotic bioengineering is considered a prevailing approach to enhance the efficacy of probiotics for targeted control of pathogens. Here, the ability of Lactobacillus casei expressing the L. monocytogenes invasion proteins Internalins A and B ( inl AB ) to prevent infection was investigated. The inl AB operon was cloned and surface‐expressed on L. casei resulting in a recombinant strain, Lbc Inl AB , and subsequently, its ability to inhibit adhesion, invasion and translocation of L. monocytogenes through enterocyte‐like Caco‐2 cells was examined. Cell surface expression of Inl AB on the Lbc Inl AB was confirmed by Western blotting and immunofluorescence staining. The Lbc Inl AB strain showed significantly higher ( P  <   0.0001) adherence, invasion and translocation of Caco‐2 cells than the wild‐type L . casei strain (Lbc WT ), as well as reduced L. monocytogenes adhesion, invasion and transcellular passage through the cell monolayer than Lbc WT . Furthermore, pre‐exposure of Caco‐2 cells to Lbc Inl AB significantly reduced L. monocytogenes ‐induced cell cytotoxicity and epithelial barrier dysfunction. These results suggest that Inl AB ‐expressing L . casei could be a potential practical approach for prevention of listeriosis.