Role of bacterial adhesion in the pathogenesis of cholera

In studies with the adult-rabbit ileal-loop model, antibodies to the lipopolysaccharide somatic-antigen component of Vibrio cholerae gave passive protection against challenge with live V. cholerae. The antisomatic antibodies had no effect on bacterial proliferation and toxin production either in vivo or in vitro; after challenge, antibody-protected and non-protected rabbit ileal loops developed almost identical amounts of cholera toxin and numbers of V. Cholerae. The protection could be correlated only with a 10-15-fold reduction in the number of V. cholerae adherent to the mucous membrane of the antibody-protected loops. The amount of cholera toxin in the two sets of loops ranged from 1600 to 3200 units. In contrast, when biologically active cholera toxin was prepared in vitro, the amount required to induce ileal-loop secretion was very large (25,600 units). These findings indicate that toxin production by adherent vibrios on the surface of the mucous membrane is an important factor in the pathogenesis of cholera.