Isolation, whole genome sequencing and application of a broad-spectrum Salmonella phage

Salmonella is considered as one of the most common zoonotic /foodborne pathogens in the world. The application of bacteriophages as novel antibacterial agents in food substrates has become an emerging strategy. Bacteriophages have the potential to control Salmonella contamination.We have isolated and characterized a broad-spectrum Salmonella phage, SP154, which can lyse 9 serotypes, including S. Enteritidis, S. Typhimurium, S. Pullorum, S. Arizonae, S. Dublin, S. Cholerasuis, S. Chester, S. 1, 4, [5], 12: i: -, and S. Derby, accounting for 81.9% of 144 isolates. SP154 showed a short latent period (40 min) and a high burst size (with the first rapid burst size at 107 PFUs/cell and the second rapid burst size at approximately 40 PFUs/cell). Furthermore, SP154 activity has higher survival rates across various environmental conditions, including pH 4.0-12.0 and temperatures ranging from 4 to 50 °C for 60 min, making it suitable for diverse food processing and storage applications. Significant reductions in live Salmonella were observed in different foods matrices such as milk and chicken meat, with a decrease of up to 1.9 log₁₀ CFU/mL in milk contamination and a 1 log₁₀ CFU/mL reduction in chicken meat. Whole genome sequencing analysis revealed that SP154 belongs to the genus Ithacavirus, subfamily Humphriesvirinae, within the family Schitoviridae. Phylogenetic analysis based on the terminase large subunit supported this classification, although an alternate tree using the tail spike protein gene suggested affiliation with the genus Kuttervirus, underscoring the limitations of relying on a single gene for phylogenetic inference. Importantly, no virulence or antibiotic resistance genes were detected in SP154. Our research highlights the potential of using SP154 for biocontrol of Salmonella in the food industry.