Many microbial pathogens, including those responsible for major enteric infections, exploit oligosaccharides that are displayed on the surface of host cells as receptors for toxins and adhesins. Blocking crucial ligand receptor interactions is therefore a promising therapeutic strategy. One approach is to express molecular mimics of host receptors on the surface of harmless recombinant bacteria that can survive in the gut. These recombinant probiotics bind bacterial toxins in the gut lumen with very high avidity, thereby preventing disease.