Flagella from F18+ Escherichia coli play a role in adhesion to pig epithelial cell lines

F18 fimbriae and toxins produced by F18 fimbriae-carrying Escherichia coli (E. coli) strains are known virulence factors responsible for post-weaning diarrhea (PWD) and edema disease (ED). In this study, we showed that fliC isogenic mutants constructed in two reference wild-type F18 fimbriae (F18+) E. coli were markedly impaired in adherence in vitro cell models (p < 0.05). Flagella purified from F18+ E. coli could directly bind to cultured piglet epithelial cells and block adherence of F18+ E. coli to cells when pre-incubated. In addition, the F18+ E. coli fliC deletion mutants up-regulated the expression of type I fimbriae produced by F18+ E. coli strains. These results demonstrated that expression of flagella is essential for the adherence of F18+ E. coli in vitro.