Characterization of broad-host-range Salmonella phage GSP006 and its efficacy in controlling Salmonella Pullorum contamination in poultry feed and drinking water

Salmonella enterica subsp. enterica serovar Pullorum (Salmonella Pullorum) is the major pathogen that is harmful to the poultry industry in developing countries. It causes acute systemic and severe gastrointestinal diseases in chicks, resulting in high mortality. As a natural alternative to conventional antimicrobial agents, phage therapy is increasingly recognized as highly effective and promising for the control of multidrug-resistant bacterial infections, including salmonellosis caused by Salmonella. In this study, a broad-host-range phage, GSP006, targeting Salmonella Pullorum was isolated from poultry farm wastewater. It exhibited lytic activity against Salmonella Pullorum, Salmonella Enteritidis, Salmonella Typhimurium and other Salmonella serotypes. Genomic analysis revealed that GSP006 possesses a double-stranded DNA (dsDNA) genome of 42,165 bp with a G + C content of 50%. Phylogenetic analysis based on the terminase large subunit confirmed that GSP006 belongs to the genus Jerseyvirus. Biological characterization showed that phage GSP006 was stable to heat (4 °C to 60 °C) and pH (pH 3 to pH 11). A one-step growth curve analysis revealed a short latent period of approximately 20 min, followed by a pronounced lysis phase. In vitro experiments, phage GSP006 was able to inhibit the bacterium for more than 6 h at 37 °C under different infection multiplicities. Furthermore, in antimicrobial assays using poultry feed and drinking water matrices, GSP006 (at MOIs of 100, 1,000, and 10,000) significantly reduced the load of Salmonella Pullorum. These results suggest that phage GSP006 may serve as a preventive measure against the horizontal transmission of Salmonella Pullorum. The broad-host-range phage GSP006 demonstrates excellent environmental stability and significantly reduces Salmonella Pullorum levels in poultry feed and drinking water under controlled laboratory conditions. This study establishes a foundation for its potential development as an effective biocontrol agent to reduce the horizontal transmission of Salmonella Pullorum.