Phage-based biocontrol of Salmonella and E. coli in Raw Chicken Fillets: Optimizing Phage-Based Solutions to Enhance Food Safety Under Cooled Storing Conditions

Oleksandra Berhilevych^*Elisa PehJohanna VahleMadeleine PlötzSophie Kittler^*

• University of Veterinary Medicine Hannover, Hanover, Germany

Food safety continues to be an important issue for consumer protection and public health, globally. Chicken meat is considered a primary source of Salmonella and E. coli infections in humans. This study aimed to develop and evaluate the effectiveness of a three-phage cocktail with optimized efficacy for simultaneously controlling Salmonella and E. coli on raw chicken fillets during cold storage. Phages were combined in a cocktail and the host range was expanded using the Appelmans protocol. The antibacterial efficacy of the trained three-phage cocktail was evaluated in liquid culture and on raw chicken fillets at 4 ± 0.5 °C for 72 h using multiplicities of infection (MOI) of 1, 10, and 100 for targeting fillets contaminated with single Salmonella and E. coli strains and a mixture of both. After training according to the Appelmans protocol, the cocktail showed expanded host range, covering 62.5% (5/8 after 30 training cycles) instead of 37.5% (3/8 before training) of the tested bacteria. Assays in liquid culture demonstrated that the trained three-phage cocktail had a significant inhibitory effect on bacterial growth of the Salmonella strains (4/4, 100%) from 3 to 6 h while the non-trained initial three-phage cocktail´s effect was less pronounced (1/4, 25%) and lasted only 3 h. However, three of four E. coli strains (75%), were not sensitive to the three-phage cocktail after 30 cycles of the Appelmans protocol compared to two out of four strains (50%) for the non-trained initial three-phage cocktail. On raw chicken fillets, significant bacterial reduction was observed when using MOI 10, and 100 of the trained three-phage cocktail. A maximum reduction of 1.56 log10 CFU/mL of Salmonella BfR 20-SA00418 and 1.48 log10 CFU/mL of E. coli 19/302/1/A after 72 h compared to placebo-treated controls were achieved using a MOI of 100. The efficacy of the developed three-phage cocktail and its ability to reduce bacterial load in raw chicken fillets highlighted its potential for extending shelf life and reducing risks for the consumer. The findings of this study demonstrate that the developed and optimized three-phage cocktail, is a promising biocontrol agent for enhancing safety in raw chicken meat production.