Effect of Propionibacterium freudenreichii on Salmonella multiplication, motility, and association with avian epithelial cells

We investigated the effects of a probiotic bacterium, Propionibacterium freudenreichii, on Salmonella multiplication, motility, and association to and invasion of avian epithelial cells in vitro. Two subspecies of P. freudenreichii (P. freudenreichii subsp. freudenreichii and P. freudenreichii subsp. shermanii) were tested against 3 Salmonella serotypes in poultry, namely, S. Enteritidis, S. Typhimurium, and S. Heidelberg, using co-culture-, motility, multiplication, cell association, and invasion assays. Both strains of P. freudenreichii were effective in reducing or inhibiting multiplication of all 3 Salmonella serotypes in co-culture and Turkey cecal contents (P ≤ 0.05). P. freudenreichii significantly reduced Salmonella motility (P ≤ 0.05). Cell culture studies revealed that P. freudenreichii associated with the avian epithelial cells effectively and reduced S. Enteritidis, S. Heidelberg, and S. Typhimurium cell association in the range of 1.0 to 1.6 log₁₀ CFU/mL, and invasion in the range of 1.3 to 1.5 log₁₀ CFU/mL (P ≤ 0.05), respectively. Our current in vitro results indicate the potential of P. freudenreichii against Salmonella in poultry. Follow-up in vivo studies are underway to evaluate this possibility.