This paper is devoted to a review of information pertinent to the role of Bacillus cereus as a food-borne pathogen. Primary emphasis is on the properties of B. cereus and published accounts of its involvement in animal and human disease. Methods for isolation, identification, and enumeration are discussed. Research needs pertaining to (a) recognition of the potential public health hazard and (b) further investigation of the food poisoning syndrome are presented.

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An enterotoxin synthesized during exponential growth by Bacillus cereus produces fluid accumulation in rabbit ileal loops, alters vascular permeability in the skin of rabbits, and kills mice when injected intravenously. All activities are eluted simultaneously from a Sephadex G-75 column and are distinct from the hemolysin and egg yolk turbidity factor of B. cereus. The enterotoxin is a true exotoxin. It interacts with intestinal receptor sites in a highly transient manner in the ileal loop system. Rabbit immune serum produced against the culture fluids from one strain of B. cereus neutralized the three biological activities in all other strains tested except strain B-6-ac for which none of the activities were neutralized. Enterotoxin proved to be unstable under a wide variety of conditions; ionic strength was especially critical. Enterotoxin was most stable in a pH range of 5.0 to 10.0, but lost activity rapidly outside this range. Alkylation provided some protection of enterotoxin activity in crude preparations but failed to protect activity during purification procedures. It did not appear to affect critically the enterotoxin molecule itself, since elution profiles on Sephadex G-75 chromatography were unchanged after alkylation.

SUMMARY The growth of salmonellae was observed to occur at pH values as low as 4.05 × 0.05. The growth‐limiting pH was dependent on several factors, most important the acid molecule itself. Additionally, the effect of temperature, relative oxygen supply and level of inoculum was studied. The salmonellae could not be “trained” to grow at a lower pH by sequential transfer at nearoptimum pH values.

Crude culture filtrates of strains of Bacillus cereus, B. thuringiensis, and B. mycoidls 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 similai 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.