Alteration of vascular permeability in rabbits by culture filtrates of Bacillus cereus and related species.

Crude culture filtrates of strains of Bacillus cereus, B. thuringiensis, and B. mycoides caused an increase in vascular permeability when injected intradermally into rabbits. The time course of the change in permeability was determined, and could easily be distinguished from a more transient effect induced by purified (from B. cereus) phospholipase C. The properties of the responsible factor were found to be similar to those reported for the guinea pig dermal factor and the ileal loop fluid inducing factor, namely: synthesis by vigorously aerated, logarithmically growing cells; inactivation by heating at 56 C; non-dialyzability; precipitation with ammonium sulfate; and antigenic characteristics. Permeability factor was not related to either the phospholipase C or the hemolysin produced by B. cereus. Activity of this B. cereus toxin, as measured in the vascular permeability and ileal loop assays, can easily be quantitated, but the greater simplicity, reliability, and economy of the vascular permeability test make it the method of choice for screening cultures or following toxin purification.