Growth and Toxin Production by Clostridium botulinum in Sauteed Onions.

In October, 1983, sauteed onions in "patty-melt" sandwiches were epidemiologically responsible for a large outbreak of botulism in Peoria, Illinois. Spores of strains of Clostridium botulinum type A, recovered from Spanish onions or from patients who consumed sauteed onions, produced high toxin titers within 48 h from 2 spores/g of onions when experimentally inoculated into sauteed onions. Laboratory strains of C. botulinum type A which normally produce high-titered toxin in culture media yielded very low toxin titers and required 3 to 4 d and an extremely high inoculum of spores/g of onions. Five strains of C. botulinum type A were isolated from 75 raw onions obtained from the Peoria restaurant where the outbreak occurred.