Three strains each of S. Typhimurium were obtained from the bacterial culture collection of Seoul National University for this study. Each strain of S.Typhimurium was grown in 15 ml of tryptic soy broth at 37 °C for 24 h and harvested by centrifugation at 4000 ×g at 4 °C for 20 min, then washed three times with buffered peptone water Cells in the final pelletwere resuspended in sterile BPW, corresponding to approximately 107–108 CFU/ml and combined to construct a threestrain
culture cocktail.