Salmonella Typhimurium (S. Typhimurium) contamination poses a significant challenge to breeder egg hatchability and chick health, necessitating the exploration of alternative disinfection methods. This study investigates the potential of phage vB_SPuM_SP02 (SP02) as a novel disinfectant for breeder eggs contaminated with S. Typhimurium SM022. Phage SP02 was isolated from poultry farm effluent and characterized for morphology, biological properties, and genome properties. Experimental groups of specific pathogen-free (SPF) eggs were treated with Salmonella and phage SP02, and efficacy was assessed through hatching rates, chick survival, weight, Salmonella load, immune organ indices, and intestinal flora. Phage treatment effectively eradicated Salmonella contamination on eggshells within 12 h, resulting in increased hatching and survival rates compared to controls. Furthermore, phage treatment mitigated weight loss and tissue Salmonella load in chicks without causing immune organ damage while reducing Salmonella spp. abundance in the intestinal tract. This study demonstrates the potential of phage SP02 as an eco-friendly and efficient disinfectant for S. Typhimurium-contaminated breeder eggs, offering promising prospects for practical application in poultry production.

Colibacillosis caused by avian pathogenic Escherichia coli (APEC) remains an important bacterial disease in poultry production and is increasingly difficult to control because of antimicrobial resistance. In this study, a lytic phage, ND-4, was isolated from poultry-farm sewage using the O2:K1 APEC strain IMT5155 as the host, and its biological characteristics, genome features and preliminary application potential were evaluated. ND-4 formed clear plaques on IMT5155 and showed a tailed morphology, with an elliptical head of 110 ± 5 nm by 82 ± 5 nm and a tail of 97 ± 5 nm by 18 ± 2 nm, giving a total virion length of approximately 204 ± 10 nm. The phage had an optimal multiplicity of infection of 0.01, a latent period of 20 min, a 50 min burst period and a burst size of 231 PFU/cell. ND-4 remained active across pH 4–9 and at temperatures up to 60 °C, and it retained titers above 10⁸ PFU/mL after exposure to chloroform concentrations up to 15%. Whole-genome sequencing revealed a 154,669 bp double-stranded DNA genome with 184 predicted open reading frames and a G + C content of 48.98%. No virulence or antimicrobial resistance genes were detected. ND-4 reduced biofilm biomass in vitro and decreased tissue bacterial loads and alleviated hepatic inflammation and vacuolar degeneration in IMT5155-challenged chicks. These results indicate that ND-4 is a promising candidate for further development as a phage-based control agent against APEC infection, although larger in vivo studies are needed to define its efficacy, dosing window and biosafety profile.