Figure 2

In vitro assessment of adhesion, invasion, intracellular survival, and stress. A. Adhesion, B. Invasion, and C. Intracellular survival. The strengths of adhesion, invasion, and intracellular survival of JOL2782 and JOL2837 were compared against those of the Salmonella JOL401 WT strain using RAW 264.7 cells, HEK293T cells, Caco-2 cells, and IEC-6 cells. Monolayer cells were infected with each strain at 40 MOI. The adhesion and invasion of each strain were assessed after 30 min and 2.5 h of incubation. Intracellular survival was evaluated 12 h post-infection. D. Stress survival of Salmonella WT strain JOL401 and attenuated strains JOL2782 and JOL2837 exposed to acid and oxidative H₂O₂ stresses. The susceptibility of strains was compared after 30 min of exposure. The survival of strains was determined based on the respective initial inoculum. E. Expression of virulence genes. Salmonella strains JOL401, JOL2782, and JOL2837 were exposed to the stress of 1 mM and 5 mM H₂O₂ at pH 4.0 for 30 min, and RNA was extracted for real-time PCR analysis. The expression of selected virulence genes was evaluated by normalizing against the housekeeping rrsG gene. Data were analysed by multiple unpaired t tests and are presented as *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001.