Phenotypes of ΔompR. a) WT or ΔompR was characterized for the ability to survive under a range of environmental stresses associated with macrophage-killing mechanisms. The '% survival' values indicate the percentage of viable bacteria after exposure to the environmental stresses. b) WT or ΔompR was used to infect macrophages so as to investigate bacterial resistance to phagocytosis in vivo and adhesion on the cell surface. The percentage of cell-associated bacteria was determined by dividing the total number of cell-associated bacteria into the total CFU in the inoculum, while the percentage of phagocytosis was calculated by dividing the number of cell-associated bacteria by the number of intracellular bacteria. Finally, student's t test was carried out to determine the statistical significance (P < 0.05).