Young Scholar Presentation: Effect of a Dairy Probiotic, Propionibacterium Freudenreichii, on Salmonella Enterica Heidelberg Colonization and Internal Organ Dissemination in Commercial Turkeys

Salmonella Heidelberg is a major non-typhoidal Salmonella serotype that causes foodborne illness in humans. Turkeys could harbor the pathogen in their ceca without showing obvious clinical signs, potentially resulting in contamination of carcasses during processing. Since humans could contract salmonellosis by consuming S. Heidelberg contaminated turkey products, targeted control measures minimizing the colonization of the pathogen in turkeys are required. Probiotics are one of the commonly used non-antibiotic interventions that can be used to control foodborne pathogens in food animal agriculture. The current study investigated the efficacy of a dairy-origin probiotic bacterium, Propionibacterium freudenreichii strain N3523 (PF) against S. Heidelberg using in vitro and in vivo experiments. The in vitro experiments included motility-, multiplication-, adhesion- and invasion assays in modified motility medium, cecal contents, and avian epithelial cell lines, respectively. In addition, probiotic qualities of PF were tested by exposing it to low pH, and bile salts, and conducting hemolysis-, antibiotic susceptibility-, antimicrobial activity-, and adhesion and invasion- assays. Follow up in vivo experiments were conducted in 2-week, 7-week, and 12-week old commercial turkeys to determine the efficacy of PF against S. Heidelberg colonization. For all in vitro assays, the treatments were duplicated and the experiments were repeated at least 3 times. For in vivo studies, each treatment group had at least 12 birds, and the experiments were repeated. Data were analyzed using the PROC-MIXED procedure of SAS, with a P<0.05 determining statistical significance. The in vitro results revealed that PF was effective in reducing S. Heidelberg motility, multiplication, adhesion, and invasion to avian epithelial cells (P<0.05). PF possessed high survival rate in low pH and in the presence of bile salts. PF did not possess hemolytic activity and showed susceptibility to the common antibiotics, ensuring the safety for use in turkeys. Additionally, the cell-free extracts of PF possessed antimicrobial activity against pathogens, including S. Heidelberg (P<0.05). In the in vivo experiments, the reduction in the S. Heidelberg populations ranged from 1.0- to 2.7- log₁₀ CFU/g of the cecum in different age groups (P<0.05). In addition, PF supplementation significantly reduced S. Heidelberg invasion of liver and spleen of turkeys (P<0.05). PF colonized in high numbers (~5.0 log₁₀ CFU/g) in the cecum, indicating its high adherence potential. In conclusion, PF could be used as an effective probiotic in turkeys to prevent S. Heidelberg colonization and dissemination to internal organs. The research was financially supported by the Minnesota AES Project (State Special).