Antibacterial efficacy of a broad lytic spectrum phage against Salmonella in different food matrices and broilers.

Salmonella enterica is a major public health concern due to its widespread contamination of food products and the increasing prevalence of multidrug-resistant strains. Bacteriophage-based biocontrol has emerged as a safe and effective alternative to conventional antibiotics. Here, we isolated and characterized the broad-spectrum lytic phage vB_SgulP_SP124, which lysed 81.08% of 148 tested Salmonella strains across five clinically important serotypes: S. Enteritidis, S. Typhimurium, S. Pullorum, S. Choleraesuis, and S. Dublin. The phage exhibited high viability across a pH range of 2-10 and temperatures ranging from 4°C to 60°C. Its 40,499 bp dsDNA genome (G + C content 49.60%) was classified within the class Caudoviricetes, subfamily Guernseyvirinae, and genus Jerseyvirus. Genomic analysis confirmed the absence of virulence, lysogeny, or antibiotic resistance genes, supporting its safety profile for biocontrol applications. In planktonic assays conducted at the optimal multiplicity of infection of 0.01, the phage significantly inhibited the growth of four Salmonella strains, with viable counts of two strains reduced within 2 h. Moreover, the phage significantly reduced S. Enteritidis levels on chicken breast, milk, liquid egg, and lettuce during 36 h of storage at 4°C. Pharmacokinetic analysis in specific pathogen-free broilers showed that intraperitoneal (IP) administration provided superior phage persistence and biodistribution compared with oral and intramuscular routes. Both early and delayed IP phage treatment significantly lowered bacterial burdens in blood and organs, although early intervention showed a consistent (but non-significant) trend toward greater efficacy. These results establish phage vB_SgulP_SP124 as a promising biocontrol agent for Salmonella contamination across the farm-to-table continuum.