Salmonella Phage X5 Alleviates Salmonella pullorum-Induced Growth Impairment in Chickens: Associations with Reduced Salmonella Burden, Modulated Intestinal Microbiome and Attenuated Inflammatory Responses

Salmonella infection of chickens can cause persistent intestinal inflammation, intestinal microbiota disorder, and growth obstruction, which is an important bacterial disease causing significant economic losses in poultry farming. Phages, as an alternative to antibiotics as biological control agents, have advantages such as precise killing and no residue. This study aims to explore the effect and mechanism of the lytic Salmonella phage X5 in alleviating the growth impairment in chickens caused by S. pullorum. Oral administration of phages effectively prevents and controls S. pullorum infection in chickens. Phages can alleviate growth impairment caused by Salmonella, reduce Salmonella levels in the liver and ileum, lower serum concentrations of IL-1β, IL-6, and TNF-α, and decrease mRNA expression of inflammatory cytokines IL-1β and IL-6 in the ileum. They also enhance mRNA expression of tight junction proteins Claudin-3 and ZO-1 in the ileal mucosa, helping maintain intestinal barrier integrity, and modulate the microbial community composition in the cecum. In the context of reduced and restricted antibiotic usage in livestock production, this study initially verified the protective effect of phage X5 against Salmonella pullorum infection in chickens, providing an experimental basis for the application of phages in the prevention and control of this bacterial disease, and offering new clues for analyzing the potential pathways through which bacteriophages confer host protective effects.