Broad-Spectrum <i>Salmonella</i> Phages PSE-D1 and PST-H1 Controls <i>Salmonella</i> in Foods

Food contamination by <i>Salmonella</i> can lead to serious foodborne diseases that constantly threaten public health. Innovative and effective strategies are needed to control foodborne pathogenic contamination since the incidence of foodborne diseases has increased gradually. In the present study, two broad-spectrum phages named <i>Salmonella</i> phage PSE-D1 and <i>Salmonella</i> phage PST-H1 were isolated from sewage in China. Phages PSE-D1 and PST-H1 were obtained by enrichment with <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Enteritidis (<i>S.</i> Enteritidis) CVCC1806 and <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Typhimurium (<i>S.</i> Typhimurium) CVCC3384, respectively. They were able to lyse <i>Salmonella</i>, <i>E. coli</i> and <i>K. pneumoniae</i> and exhibited broad host range. Further study demonstrated that PSE-D1 and PST-H1 showed high pH and thermal tolerances. Phage PSE-D1 belongs to the <i>Jiaodavirus</i> genus, <i>Tevenvirinae</i> subfamily, while phage PST-H1 belongs to the <i>Jerseyvirus</i> genus, <i>Guernseyvirinae</i> subfamily according to morphology and phylogeny. The results of genome analysis showed that PSE-D1 and PST-H1 lack virulence and drug-resistance genes. The effects of PSE-D1 and PST-H1 on controlling <i>S.</i> Enteritidis CVCC1806 and <i>S.</i> Typhimurium CVCC3384 contamination in three kinds of foods (eggshells, sausages and milk) were further investigated, respectively. Our results showed that, compared to phage-free groups, PSE-D1 and PST-H1 inhibited the growth of their host strain significantly. A significant reduction of host bacteria titers (1.5 and 1.9 log₁₀ CFU/sample, <i>p</i> < 0.001) on eggshells was observed under PSE-D1 and PST-H1 treatments, respectively. Furthermore, administration of PSE-D1 and PST-H1 decreased the counts of bacteria by 1.1 and 1.2 log₁₀ CFU/cm² (<i>p</i> < 0.001) in sausages as well as 1.5 and 1.8 log₁₀ CFU/mL (<i>p</i> < 0.001) in milk, respectively. Interesting, the bacteriostasis efficacy of both phages exhibited more significantly at 4 °C than that at 28 °C in eggshells and milk and sausages. In sum, the purpose of our research was evaluating the counteracting effect of phage PSE-D1 and PST-H1 on the spread of <i>Salmonella</i> on contaminated foods products. Our results suggested that these two phage-based biocontrol treatments are promising strategies for controlling pathogenic <i>Salmonella</i> contaminated food.