Isolation, Characterization, and In Vivo Evaluation Efficacy of Lytic Bacteriophage SEP1 Against Salmonella Paratyphi C.

Multidrug-resistant Salmonella Paratyphi poses a severe threat to public health. As conventional antibiotics lose efficacy against emerging resistant strains, the need to develop alternative antimicrobial agents has become increasingly urgent. In this study, we isolated and characterized a novel lytic bacteriophage, designated SEP1, from poultry sewage using the S. Paratyphi C strain QH as the host and systematically evaluated its therapeutic potential in a murine infection model Genomic analysis confirmed that SEP1 belongs to the genus Felixounavirus, with an 85,703-bp genome devoid of lysogeny-associated or virulence genes. SEP1 exhibits robust environmental stability, maintaining infectivity at 10-50 °C and pH 4-9; it has a 30 min latent period and a burst size of 133 PFU per infected cell. In vivo, SEP1 treatment conferred 100% survival in infected mice, reduced organ bacterial loads, alleviated tissue damage, and normalized inflammatory cytokine profiles. Collectively, these results demonstrate that SEP1 is a promising candidate for phage therapy targeting S. Paratyphi C infections.