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

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 (inlAB) to prevent infection was investigated. The inlAB 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 InlAB 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 InlAB‐expressing L. casei could be a potential practical approach for prevention of listeriosis.