Figure 5.

SrrG and CsrS mutations enhance the lethality and histopathology of SDSE in in vivo mouse models.

(a) Survival curves of mice infected with each strain. Mice were intra-peritoneally inoculated with 6 × 10⁷ CFUs of each SDSE and survival was observed up to 7 days post-infection. Differences in mortality were statistically significant (p < 0.01 by a log-rank test), as determined by a log-rank test. Survival curves were generated from 3 independent experiments using a total of 15 ddY mice per strain. (b) Counts of SDSE in 100 μL blood of each male ddY mouse. Blood was withdrawn 21 h post injection and bacterial counts were determined by plating on agar. The (–) bar represents median values, *(p < 0.05 by z-test). (c–d) Histopathological changes in the lung (c) and kidneys (d) of SDSE infected mice. Tissues were extracted 21 h post intra-peritoneal injection with 3 × 10⁷ CFUs of SDSE. Black arrows indicate clusters of bacteria in lungs (c) and kidneys (d). The scale bar indicates 100 μm. (e-g) Lesion areas of subcutaneous infection in hairless mice injected with SDSE. (e) 3 × 10⁷ CFUs of SDSE was injected subcutaneously, and lesion area were measured daily post infection (n = 5). Lesion areas in mice infected with srrG or csrS mutant strains were significantly larger than in those infected with wild type SrrG strains (SDSE80) (* p < 0.05; ** p < 0.01 using the z-test). Error bars displayed as mean +/- SD. Representative gross (f), and microscopic histopathological findings (g) in mice infected with SDSE. (g) Black arrows indicate clusters of bacteria. The scale bar indicates 500 μm.