The strains of S. Typhimurium 4/74 or S. Enteritidis P125109 were used in this study. Bacteria were cultured for 16 h
aerobically in nutrient broth (NB, Oxoid, UK). Culture (5 ml)was transferred into 100 ml NB, and grown until the OD reached
between 0.5–0.8; cells were then pelleted at 2500×g, 4◦C, for 20 min. The bacterial pellet was resuspended in 5ml of PBS
and sonicated on ice for a total of 5min at 15× 10 s pulses at amplitude of 37 (Vibra cell; Sonics &Materials, Inc. – 500 Watt
Ultrasonic processor, Model No. VCX 500, USA). Bacterial lysate was stored at −20 ◦C until use.