Contribution of the <i>csgA</i> and <i>bcsA</i> genes to <i>Salmonella enterica</i> serovar Pullorum biofilm formation and virulence

<p><i>Salmonella</i> biofilm formation is important to environmental stress resistance and virulence. However, the roles of the <i>csgA</i> and <i>bcsA</i> genes, which affect curli protein and cellulose production, respectively, in <i>Salmonella enterica</i> serovar Pullorum, are unknown. Here we constructed deletions in the <i>csgA</i> and <i>bcsA</i> genes in <i>S. enterica</i> serovar Pullorum strain S6702 and evaluated several aspects of biofilm formation and virulence. Δ<i>csgA</i> showed decreased production of curli fimbriae, while Δ<i>bcsA</i> had reduced cellulose production. Both mutants had a reduced ability to form biofilms. Δ<i>csgA</i> was reduced in adhesion and invasion to HeLa cells and exhibited decreased intracellular proliferation in HD11 macrophages. Δ<i>bcsA</i> exhibited increased proliferation in HD11 cells and replicated better in chicken spleens, as compared to the wild-type strain. Δ<i>csgA</i> virulence was attenuated in assays involving oral challenge of one-day-old chickens.</p>