Activity of a Bacteriophage Cocktail to Control Salmonella Growth Ex Vivo in Avian, Porcine, and Human Epithelial Cell Cultures

We examined the activity of phages to control the growth of chicken and swine Salmonella strains in avian (CHIC-8E11), porcine (IPEC-1), and human (HT-29) cell cultures. We optimized a six-phage cocktail by selecting the five most effective myoviruses and a siphovirus that have optimal lysis on prevalent serovars. We observed ∼20% of 7 log₁₀ PFU/well phage and 3-6 log₁₀ CFU bacterial adhesions, and 3-5 log₁₀ CFU bacterial invasion per 2 cm² of the cultured cells at 2 h post-treatment. The invasive bacteria when plated had a variable reduced susceptibility to the phages. After phage application at an MOI of 10, the prophylaxis regimen had better efficacy at controlling bacterial growth with an up to 6 log₁₀ CFU/well reduction as compared with the 1-2 log₁₀ CFU/well bacterial reduction observed in the remedial and coinfection regimens. Our data support the development of these phages to control salmonellosis in chickens, pigs, and humans.