An emetic toxin cereulide, produced by Bacillus cereus, causes emetic food poisonings, but a method for quantitative measurement of cereulide has not been well established. A current detection method is a bioassay method using the HEp‐2 cell vacuolation test, but it was unable to measure an accurate concentration. We established a quantitative assay for cereulide based on its mitochondrial respiratory uncoupling activity. The oxygen consumption in a reaction medium containing rat liver mitochondria was rapid in the presence of cereulide. Thus uncoupling effect of cereulide on mitochondrial respiration was similar to those of uncouplers 2,4‐dinitrophenol (DNP), carbonylcyanide m‐chlorophenylhydrazone (CCCP), and valinomycin. This method gave constant results over a wide range of cereulide concentrations, ranging from 0.05 to 100 μg/ml. The minimum cereulide concentration to detect uncoupled oxygen consumption was 50 ng/ml and increased dose‐dependently to the maximum level. Semi‐log relationship between the oxygen consumption rate and the cereulide concentraiton enables this method to quantify cereulide. The results of this method were highly reproducible as compared with the HEp‐2 cell vacuolation test and were in good agreement with those of the HEp‐2 cell vacuolation test. The enterotoxin of B. cereus or Staphylococcus aureus did not show any effect on the oxygen consumption, indicating this method is specific for the identification of cereulide as a causative agent of emetic food poisonings.

We report the complete and annotated genome sequence of Bacillus cereus NC7401, a representative of the strain group that causes emetic-type food poisoning. The emetic toxin, cereulide, is produced by a nonribosomal protein synthesis (NRPS) system that is encoded by a gene cluster on a large resident plasmid, pNCcld.

Alcohols showed bactericidal activity against Staphylococcus aureus, Micrococcus luteus, Escherichia coli, and Enterobacter cloacae suspended in 0.85% (v/v) saline in the order of n-butanol>n-propanol>ethanol>methanol.Against the bacteria suspended in n-octane, however, alcohols showed a reverse order of bactericidal effectiveness.When toluene as a hydrophobic solvent was mixed with a small amount of hydrophilic methanol (5 or 10%, v/v) , or conversely, when hydrophilic methanol was mixed with a small amount of hydrophobic nhexane (10 or 30%, v/v) , the bactericidal activity of the mixture increased markedly. The pattern of the relative glucose-Sudan III solubility curve was similar to that of the bactericidal activity curve of ethanol solutions. The results obtained suggest that the bactericidal activity of an alcohol was not dependent on the logarithm of the partition coefficient of the alcohol but on the hydrophobicity-hydrophilicity balance of the solution.