Expression of TviA in <i>S.</i> Typhimurium reduces early host responses.

<p>Bovine ligated ileal loops (N = 4 animals) were mock treated (LB broth) or infected with a <i>S.</i> Typhimurium ATCC14028 <i>phoN</i> mutant (AJB715), a <i>phoN</i>::<i>viaB</i> mutant (TH170), a <i>phoN</i>::<i>tviA</i> mutant (SW474), or a <i>phoN invA</i> mutant (SW737) pre-cultured in LB broth. Samples were collected 5 h after infection. (A) Bacterial load in the tissue was determined by treating tissue biopsies with Gentamicin and plating on selective media. Bars represent geometric means of bacterial loads ± standard error. (B) Fluid accumulation recorded 5 h after infection. Data is expressed as a percent of the response observed in loops infected with the <i>phoN</i> mutant (maximum response). Bars represent geometric means ± standard error. (C) Pathological changes in the ileal mucosa. Formalin-fixed ileal tissue was scored by the following criteria: hemorrhage (purple bars), infiltration with neutrophils (black bars), presence of edema (white bars), and necrosis/apoptosis (grey bars). Bars represent the average obtained from 4 animals. (D) Representative images of hematoxilin and eosin-stained sections of the ileal mucosa (magnification 60×). *, <i>P</i><0.05; **, <i>P</i><0.01; ns, not statistically significant.