Purpose: The purpose of this study was to develop phage-resistant LC (φrLC) and LP (φrLP) strains, and to evaluate their roles in reducing colonization and infection of foodborne pathogens in gut.
Methods: The secondary culture method was used to generate L. casei phage (ATCC27139-B1)-resistant and L. plantarum phage (ATCC8014-B1)-resistant mutants. Effects of mutants against growth, interactions with human intestinal epithelium cells (INT-407), and virulent genes expression of enterohemorrhagic E. coli EDL933 (ATCC700927) (EHEC), Salmonella Typhimurium LT2 (ATCC19585) (ST), and L. monocytogenes LM2 (ATCC19115) (LM) were evaluated and analyzed by ANOVA.
Results: φrLC, φrLP and their cell-free culture supernatants (CFCSs) competitively excluded/eliminated (100%) EHEC and ST within 48 h. Further, φrLC and φrLP significantly (P < 0.05) inhibited INT407 cell-pathogen interactions including adherence, invasion and virulence gene expression. For instance, the adherence abilities of EHEC, ST, and LM were reduced by φrLC by 62.1%, 68.5%, and 58.5%, respectively; and 52.7%, 61.5%, 46.9%, respectively by φrLP. Furthermore, qPCR showed that CFCSs of φrLC and φrLP down-regulated the expression levels of multiple virulence genes including 6 for EHEC (eaeA, espA, espD, fliC, hlyB, and ler), 4 for ST (fliC, fliD, hilA, and hilD), and 4 for LM (fbp, flaA, hlyA, and iap).
Significance: Bacteriophage-resistant Lactobacillus offers dairy industry a good choice on solving phage contamination; their inhibitory effects on EHEC, ST, and LM may help in reducing and preventing foodborne pathogen colonization and infections.