Bacterial resistance to SPF chicken serum and environmental stress. (A) Resistance to SPF chicken serum. Bacteria were incubated with the diluted SPF chicken serum at 37°C for 30 min. Bacteria were counted by plating on LB agar at serial dilutions. HI, heat-inactivated SPF chicken serum. (B) Resistance to environmental stress. Bacteria were examined for adaptation to environmental stresses, including alkalinity, acidity, and high osmolarity. Survival was calculated as the number of bacteria remaining after the stress exposure divided by the initial number of bacteria. Data represent averages of the results from three independent assays (*, P < 0.05).