Selective isolation and rapid identification of Clostridium botulinum types A and B by toxin detection.

A simple procedure for rapid identification of Clostridium botulinum type A and B colonies from cultures and stool samples from infants with botulism was devised. The stool samples were directly streaked on C. botulinum isolation medium containing selective inhibitory agents. Typical lipase-positive colonies that appeared within 24 to 48 h were examined for the presence of botulinal toxin by the enzyme-linked immunosorbent assay and conventional mouse toxicity test. The amount of toxin associated with 48-h colonies of stock strains was comparable to that of 96-h broth culture. The quantity of toxin present in a single colony or combination of two was shown to be sufficient for toxin detection by the enzyme-linked immunosorbent assay. Of 42 additional stock strains tested in this manner, 41 (97.5%) were identified as toxigenic C. botulinum type A or B. The remaining one strain also proved to be toxigenic when it was tested as a concentrated cell suspension. This procedure should prove useful for large-scale serological screening of food and clinical specimens.