Studies on the production of enterotoxins by Bacillus cereus

Evidence is presented for the existence of three distinct enterotoxins detected in concentrated cell-free culture filtrates of selected Bacillus cereus strains. The first was a product capable of stimulating the adenylate cyclase-cyclic-AMP system in intestinal epithelial cells and, possibly through this, causing fluid accumulation in ligated ileal sections ("loops") of young rabbits. This was elaborated by a strain isolated from an incident of diarrhoea and which caused diarrhoea in 6 of 10 monkey feedings. The second was tentatively identified as a factor which caused fluid accumulation in rabbit loops but not, apparently, through stimulation of the adenylate cyclase-cyclic-AMP system; this was elaborated by a strain isolated from raw rice which failed to produce symptoms in eight monkey feedings. Together, the behaviour of these two factors indicates that diarrhoea caused by B. cereus enterotoxin may be a cyclic-AMP-mediated event. The third, here referred to as "pyogenic toxin", caused severe tissue damage in the ileal mucosa and was elaborated by a strain isolated from a brain abscess. A factor produced by a strain isolated from an outbreak of vomiting which caused vomiting in 10 of 24 monkey feedings could bot be detected in tests reported here but appears to be a fourth enterotoxin type. Cytopathic effects in tissue cultures, suckling mouse tests, and assays of glycerol production by fat cells were not found to be of value in the detection of any of the enterotoxins.