FIG 3.
VraSRSS contributed to the full virulence of SS2. (A) Levels of vraSRSS gene expression during THB culture (in vitro) and animal infection (mouse blood, in vivo) were analyzed by qRT-PCR. The unpaired two-tailed Student's t test was used for statistical analysis (***, P < 0.001). (B) Deletion of vraSRSS resulted in significant attenuation of mortality in SS2 infection. Randomized groups of 10 SPF BALB/c mice were challenged with different bacterial strains at a dose of 5 × 108 CFU/mouse. Another 10 SPF BALB/c mice injected with PBS served as negative controls. The survival rates were monitored for 7 days after challenge. Significant differences in survival between different groups were analyzed by log-rank (Mantel-Cox) test (P < 0.05).