In vitro determination of the effects of dairy-origin Propionibacterium freudenreichii subsp. freudenreichii against multidrug-resistant Salmonella Infantis strains infective in broiler chicks

Salmonella Infantis is a major serotype of foodborne Salmonella that is emerging in poultry production. Finding novel antibacterial candidates to reduce S . Infantis colonization in broilers is critical to minimize outbreaks associated with chicken products. The current study (1) characterized two MDR outbreak strains of S . Infantis (AR0919, AR0923), individually and in Combination, for their growth and multiplication in various environmental conditions and to colonize the cecum of 2-day-old broiler chicks and dissemination to the liver ( S . Infantis characterization study) and (2) determined the in vitro effects of a dairy-originated probiotic, P. freudenreichii , on the two MDR strains of S . Infantis, individually and their Combination, on pathogen motility, epithelial cell adhesion, and invasion, and growth in various environmental conditions ( P. freudenreichii intervention study). The strains behaved similarly in vitro , individually and in Combination ( P >0.05). The in vivo study revealed that both MDR strains had a similar cecal colonization rate, individually and in Combination ( P >0.05). Strain AR0923 exhibited a higher rate of dissemination to the liver. A significant reduction in the motility, adhesion to, and invasion of Caco-2 cells and growth in co-culture media and cecal contents (both the strains and the Combination) was observed ( P <0.05). The results suggest that the two S . Infantis strains are infective in broiler chicks, and P. freudenreichii is a potential probiotic candidate against S . Infantis in vitro. Studies in commercial broiler chickens are underway.