Antibacterial Immunity to Vibrio Cholerae in Rats

School of Microbiology, University of New South Wales, P. O. Box 1 Kensington 2033, New South Wales, Australia Received October 8, 1985 Accepted November 12, 1985 Blind loops prepared in the small intestines of fasted, MgSO 4 -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 mucusborne 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.