Bacillus cereus-induced fluid accumulation in rabbit ileal loops.

The usefulness of the ligated rabbit ileal loop as an experimental model of Bacillus cereus food poisoning was investigated. Positive responses, as measured by fluid accumulation in the loop, were obtained from 19 of 22 strains of B. cereus. Four of six strains of B. thuringiensis also elicited fluid accumulation, but eight strains of other Bacillus spp. failed to evoke a response. The growth medium employed markedly affected the ability of a given strain of B. cereus to provoke a response. Brain heart infusion broth (BHI) (Difco) proved to be best for this purpose. Loop fluid-inducing activity was produced by exponentially growing cells and was present in cell-free culture filtrates and associated with washed vegetative cells. Intraluminal growth of B. cereus did not elicit fluid accumulation. Cultures grown at temperatures in the range of 18 C to 43 C were loop active. When BHI cultures of selected loop positive strains were injected intraluminally into the normal ileum of rabbits, they failed to elicit diarrhea.