E. coli 5340-2 ST only None (PBS) 0.85 0.32 Anti-TDH 0.95 + 0.32 Anti-CT 0.85 + 0.31 Normal 0.84 0.32 NOTE. Bacterial cells were suspended in either brain-heart infusion broth (for E. coli) or heart infusion broth containing 0.5% NaCl (for V. parahaemolyticus) and concentrations were adjusted to an A value at 560 nm of 100 ('v109 cells/ml) in a photometer. Aliquots of this bacterial suspension (0.5 ml) were then mixed with 0.5 ml of either phosphate-buffered saline (PBS; pH 7.2), normal rabbit serum, anti-CT, or anti-TDH (the sera were diluted threefold with PBS before use), and 1 ml of the mixture was injected into a ligated ileal loop in a rabbit. Rabbits were kept at room temperature (23 C) for 16 hr. Accumulation of fluid, measured by the FA (fluid accumulation) ratio, is expressed as ml of fluid/cm of loop length. All bacteria used were isolated from humans. * Bacteria were tested for the production of toxins related to the Kanagawa phenomenon [1] or for the production of heat-labile (LT) or heat-stable (ST) E. coli enterotoxins as described [2]. Summary