Indigenous microflora: Paving the way for pathogens?

The interface between a mammalian host organism and the microflora in its intestinal lumen is the mucous gel layer and the underlying cell coat, or glycocalyx, of glycoconjugates on the apical surface of the epithelium. Oligosaccharides within this interface can serve as receptors for the attachment of microorganisms. The first challenge to would-be luminal pathogens is successful attachment to this surface. The presence of indigenous intestinal microflora is known to interfere with colonization by pathogens, and competition for binding sites is likely to play a role in this protection. It is now apparent that the presence of indigenous intestinal microflora can also influence the expression of glycoconjugates by host epithelial cells.