Combined effects of Salmonella phage cocktail and organic acid for controlling Salmonella Enteritidis in chicken meat

Salmonella contaminated in poultry meat remains an important food safety issue as this pathogen leads to a serious foodborne illness worldwide. A number of poultry meat products have often been recalled or rejected due to Salmonella contamination leading to high economic losses each year. In poultry meat processing, various approaches with a strong bacteriostatic effect on Salmonella have been introduced including application of bacteriophages or organic acids. This study aimed to investigate the combined effects of a Salmonella phage cocktail at lower multiplicity of infection (MOI) and organic acid applied to artificially contaminated chicken meat under storage conditions. Newly isolated Salmonella phages (n = 32) showed diverse lysis profiles exhibiting lysis ability ranging from 27.7 to 87.8% on 29 serovars of Salmonella. Two selected phages, vB_SenM_P7 and vB_SenP_P32 presenting the highest lysis ability were used in a phage cocktail formulation. Acetic acid, butyric acid, propionic acid and lactic acid included in this study showed the inhibitory effect on Salmonella from 0.09 to 0.25% for the minimum inhibitory concentration (MIC) and more than 0.5% for the minimum bactericidal concentration (MBC). A phage cocktail showed highest % survival in propionic acid which was combined with the phage treatment. Use of this phage-acid combination not only could completely kill Salmonella in-vitro but could also lower Salmonella number on artificially contaminated chicken meat at 4 degrees C during a 3-day storage by 1.4 log units while a reduction of 0.4 and 1.2 log units was observed in treatment with a phage cocktail only and propionic acid only, respectively. Overall, findings suggest a combined treatment using phage and organic acid as an effective alternative for controlling Salmonella in the poultry meat industry to improve food safety.