P1-231 Bacteriophage-resistant Mutants of Lactobacillus casei and L. plantarum and Their Interaction with Foodborne Bacterial Pathogens

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Mengfei Peng, University of Maryland, College Park, MD
Serajus Salaheen, University of Maryland, College Park, MD
Debabrata Biswas, University of Maryland, College Park, MD
Introduction: L. casei (LC) and L. plantarum (LP) are widely applied in fermented food production and preparation. The antimicrobial effects of Lactobacillus may be able to prevent food spoilage. However, the activity and population density of Lactobacillus is seriously affected by bacteriophage. Replacing phage sensitive strains with phage-resistant starters offers a natural strategy to minimize phage dissemination in dairy production.

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.