Antibacterial immunity to Vibrio cholerae in rats.

Blind loops prepared in the small intestines of fasted, MgSO4-treated rats were shown to provide a simple, consistent and inexpensive means of studying mucosal colonisation by Vibrio cholerae serogroup O1. When c. 2000 cfu were injected, the number of mucosa-associated V. cholerae in each loop increased by c. 5-6 orders of magnitude in 10-14 h, without enterotoxin-induced fluid production. Scanning electronmicroscopy and culture suggested that most surface-associated organisms were present in the adherent surface mucus. V. cholerae strains varied in terms of surface-colonising capacity. Immunisation with V. cholerae given intra-intestinally greatly reduced the rate of increase and final number of mucosa-associated vibrios within the 14-h period after challenge. The method could be used to compare the immunity induced by various immunising regimens. Immunity was sometimes accompanied by intestinal mucus-borne antibody against V. cholerae lipopolysaccharide but was sometimes demonstrated in the absence of such antibody or of mucus-borne antibody to heat-sensitive surface protein.