Identification and characterization of two Campylobacter jejuni adhesins for cellular and mucous substrates

Abstract

Campylobacter jejuni is able to colonize the human intestinal mucosa and cause disease. For this reason, it was important to investigate mechanisms by which C. jejuni adheres to epithelial cells and intestinal mucus gel. All strains of C. jejuni used were able to adhere to INT 407 epithelial cells and mucus, but high adherence to one substrate did not necessarily indicate comparable adherence to the other. The adherence of C. jejuni to cells was inhibited partially by treating the bacterial cells with proteases or glutaraldehyde or by adding a certain carbohydrate (fucose or mannose) to the medium. The flagellum of C. jejuni was identified as a potential adhesin by comparing adherence of flagellated and aflagellated variants. Shearing of the bacterial cells to remove the flagella reduced bacterial adhesion, whereas immobilization of the flagellum with KCN increased adhesion. Purified flagella showed specific, fucose-resistant binding to epithelial cells but not to intestinal mucus. The presence of a second, nonproteinaceous adhesin was suggested because no single treatment of the bacteria completely inhibited adhesion. Lipopolysaccharide (LPS) was identified as another C. jejuni adhesin. [3H]LPS specifically bound to epithelial cells, and this phenomenon was inhibited by periodate oxidation of the LPS or glutaraldehyde fixation of the epithelial cells. LPS, unlike flagella, was fucose sensitive and inhibited binding of whole bacterial cells to INT 407 cells. LPS was also able to bind to intestinal mucus gel. These data indicate that both flagella and LPS are important in adhesion to the mucosal surface.