Fig. 4

In vivo validation of the phenotype of a S. Typhimurium spvC mutant. (a) The TraDIS fitness scores of transposon-insertion mutatns of spvC indicate attenuation in the ileal wall but not in MLNs. (b) Competitive index scores of ST4/74 nal^R ∆spvC::cat compared to the wild-type ST4/74 nal^R confirmed the phenotype predicted by TraDIS in the ileal wall and MLNs. CIs in the caecal lymph node were similar to those in the ileal wall but CIs in the liver and spleen show no attenuation of ST4/74 nal^R ∆spvC::cat in these tissues. CIs in faecal samples decreased over time. (c) Bacterial counts confirmed the total challenge dose of 7.2 × 10⁸ CFU of mutant and wild-type bacteria and recovery of viable bacteria per tissue per calf is shown