Each strain of E.coli O157:H7,S.Typhimurium, and L.monocytogenes was cultured in 5 ml TSB at 37 °C for 24 h, harvested by centrifugation at 4000g for 20 min at 4 °C and washed three times with sterile 0.2% peptone (Bacto, Sparks, MD). Thefinal pellets were resuspended in 0.2% sterile peptone water, corresponding to approximately 108–109 CFU/ml.Mixed culture cocktails were prepared by blending together equal volumes of each test strain