Lyophilized <i>Salmonella</i> bacteriophages remain stable and reduce pathogen loads across multiple food and feed matrices

AIMS: Salmonella is a foodborne pathogen, and the emergence of antimicrobial-resistant (AMR) strains poses a serious global threat to public health. Instead of conventional antibiotics, alternative antimicrobial strategies such as bacteriophages should be considered in the farm-to-fork chain to prevent Salmonella transmission. This study investigated the viability and antimicrobial potential of six Salmonella-specific bacteriophages, each targeting a distinct serotype, including one jumbo phage (MET P1-082). MATERIALS AND METHODS: Phage stability was first evaluated after lyophilization to determine whether the bacteriophages remained viable following this process. In addition, their stability was tested under different conditions of pH (4 and 7), temperature (4, 15, and 25°C), and salinity (0.9% and 10%) at multiple time intervals (1 h, 1 day, and 1 week). Phage titers were determined using the double agar overlay plaque assay. Based on the stability results, the antimicrobial efficacy of the phages was tested against Salmonella in artificially contaminated food matrices, including chicken feed (25°C), chicken meat (4°C), and lettuce (4°C). Reductions in Salmonella counts were quantified on Xylose Lysine Deoxycholate (XLD) agar plates. RESULTS: Titers of lyophilized phages showed average decrease of 1.3 log10 PFU mL-1. While most phages retained high stability, only MET P1-082 and MET P1-103 remained viable after 1 week at pH 4 (P < 0.001), despite a noticeable decrease in titer. Among the tested phages, the one targeting S. Kentucky achieved the highest reduction (5 log10 CFU g-1) in chicken feed after 24 h (P < 0.01). On chicken meat, the S. Infantis phage provided a 2.97 log10 CFU g-1 reduction after 24 h, while the S. Hadar phage resulted in a 2.76 log10 CFU g-1 reduction on lettuce after 1 week. CONCLUSION: The findings demonstrate that the tested bacteriophages remained stable under tested environmental conditions and effectively reduced at least 1 log10 CFU g-1 of Salmonella load in contaminated chicken feed, meat, and lettuce. These results highlight their potential as practical biocontrol agents in food safety applications.