Radioimmunoassay for Clostridium perfringens Enterotoxin and Its Use in Screening Isolates Implicated in Food-Poisoning Outbreaks

Abstract

Fourteen isolates of Clostridium perfringens obtained from food-poisoning outbreaks were screened for enterotoxigenicity using a radioimmunoassay (RIA) that detects 1.0 ng of enterotoxin/ml. Only four of the isolates produced enterotoxin in concentrations too low to be detected by counterimmunoelectrophoresis when grown in Duncan-Strong sporulation (D-S) medium. Substitution of raffinose for soluble starch or addition of theobromine to the medium stimulated enterotoxin production by three of the four enterotoxin-positive isolates. Raffinose and theobromine did not stimulate enterotoxin production by isolates that were enterotoxin-negative in D-S medium. Enterotoxin production by the RIA-positive strains correlated with the numbers of heat-resistant spores they produced. The RIA-negative isolates produced approximately the same numbers of spores/ml as the high enterotoxin producers, and more spores/ml than strain H8 produced under optimum conditions. Therefore, inability to sporulate is not the cause for failure of these isolates to produce enterotoxin. Rabbit ileal loop assays showed that the two isolates that were lowest enterotoxin producers in vitro were highly active in vivo.