A highly sensitive bacterial assay for toxins based on swarming inhibition, and comparison with the cup plate assay based on growth inhibition.

The motility inhibition of the swarming bacteria Proteus mirabilis and Azospirillum brasilense was found to be an appropriate parameter to indicate toxic effects caused by some mycotoxins, lactones and anhydrides of dicarboxylic acids. If these substances are in contact with the motile bacteria the following phenomena can be observed: at a certain toxin concentration the swarming of the bacteria is inhibited. If the concentration is increased the swarming ceases, and at still higher concentrations the bacteria are inactivated. In some instances swarming is stimulated at very low toxin doses. The sensitivity of this assay is comparable to the cup plate assay based on growth inhibition with Bacillus thuringiensis [Lenz, P. et al., Toxicology, 40 (1986) 199, Boutibonnes et al., Pharmacology, 11 (1983) 430] and in some cases it is even higher.