An investigation of the expression and adhesin function of H7 flagella in the interaction of Escherichia coli O157: H7 with bovine intestinal epithelium

wild-type levels; however, complementation with fliCH6 did not restore it. High-resolution ultra- structural and imunofluorescence studies demon- strated the presence of abundant flagella forming physical contact points with the rectal epithelium. Binding to terminal rectal epithelium was specific to H7 by comparison with other flagellin types tested. In-cell Western assays confirmed temporal expression of flagella during O157 interaction with epithelium, early expression was suppressed during the later stages of microcolony and attach- ing and effacing lesion formation. H7 flagella are expressed in vivo by individual bacteria in contact with rectal mucosa. Our data demonstrate that the H7 flagellum acts as an adhesin to bovine intesti- nal epithelium and its involvement in this crucial initiating step for colonization indicates that H7 flagella could be an important target in intervention strategies.