Isolation and Application of Salmonella Infantis-Specific Bacteriophages from Poultry-Associated Samples to Chicken Wing Flats

Abstract

The increasing need to reduce chemical interventions and the rise of antimicrobial resistance among pathogens have led poultry producers to seek alternative antimicrobial intervention methods. Research has identified bacteriophages as a promising approach to reduce Salmonella and Campylobacter at various stages of poultry production. Notably, Salmonella Infantis has emerged as an antimicrobial-resistant serotype, yet there is limited information regarding its susceptibility to bacteriophage-mediated reduction. We conducted two studies to isolate bacteriophages targeting Salmonella Infantis and to evaluate their potential to mitigate this pathogen on chicken wing flats under refrigerated conditions. As a brief explanation, for our first experiment several environmental samples were collected from four different poultry complexes and prepared as seeded and non-seeded samples for subsequent visual assessment following spot testing. We observed that seeded samples resulted in higher level of clearance of Salmonella compared to non-seeded and 9 bacteriophage isolates were obtained from 3 poultry complexes. All bacteriophages isolated exhibited high titers with Salmonella Infantis (10^9 – 10^11 PFU/mL), with three bacteriophages (SI-1, SI-2, and SI-3) showing the broadest host spectrum when tested against 13 different Salmonella serotypes. The results indicated that seeding is preferable for isolating bacteriophages, and the broad lytic activity observed against several Salmonella serotypes suggests their potential as antimicrobial interventions. In our second experiment, we evaluated the ability of three bacteriophage cocktails, comprising four bacteriophages (SI-1, SI-2, SI-3, and SI-5), to reduce Salmonella Infantis on chicken wing flats stored under refrigerated conditions. Wing flats were treated and evaluated on days 0, 3 and 7 of storage. Following two preliminary trials that showed no reduction among treatments, a third trial was conducted where wing flats were treated with 5 mL of bacteriophage cocktail and hand-massaged for 30 seconds prior to storage. Bacteriophage cocktails SI-1 and SI-3 (3.81 log10 CFU/mL), and SI-2 and SI-3 (3.99 log10 CFU/mL) exhibited lowest Salmonella Infantis counts after 7 days of storage at 4°C when compared to the control group (5.52 log10 CFU/mL). The results demonstrated the potential of bacteriophages to mitigate Salmonella Infantis under refrigerated conditions; however, different application methods will require further evaluation. Overall, the results from both studies indicate that Salmonella Infantis-specific bacteriophages exhibit a higher level of clearance when seeded and possess a broad host spectrum against various Salmonella serotypes, as well as a significant ability to reduce S. Infantis levels when applied as cocktail to chicken wing flats.