Application of salmonella phage to reduce in-vitro and in-vivo colonization of salmonella enteritidis and salmonella typhi

Background and objective: Salmonella typhi is the causative agent of enteric fever while Salmonella enteritidis causes gastroenteritis. Lytic bacteriophages can be applied as biocontrol agents to prevent Salmonella infections. The purpose of this study was to prepare a proper Salmonella phage therapy candidate to be used against pathogenic Salmonella enteritidis and Salmonella typhi. Methods: We used clinical isolates of Salmonella typhi and Salmonella enteritidis as host bacteria, to isolate Salmonella-specific phages from raw sewage water in four locations (Bahrka, Farmnbaran neighborhoods, Korey and Shaqlawa towns) in Erbil district. We assessed the efficacy of this phage as a biocontrol agent against Salmonella enteritidis in-vivo using four groups of 8 pathogen-free duck chicks. A group was kept as uninfected control while the other three groups were artificially infected with a clinical strain of Salmonella enteritidis. Two of the infected groups were treated by oral administration of phage suspension using two different doses of Salmonella enteritidis phage (7 and 12 Log10 Plague Forming Unit respectively). To compare the bacterial growth dynamics among the infected groups, one group was kept untreated. Results: We found that the four sewage samples contained bacteriophages for the two bacterial isolates with different plaque diameters and morphology. Salmonella enteritidis phage isolates collected from the Farmanbaran neighborhood showed the best lysing efficacy in-vitro hence it was selected to be tested in-vivo experiment. Phage-treatment significantly reduced the colonization burden of Salmonella enteritidis in feces and cecum contents of the experimentally infected chicks. Conclusion: These results suggest that using Salmonella phage could be a good agent to control Salmonella.