A method for estimating population levels of Clostridium perfringens in foods based on the titer of α-toxin in food extracts was evaluated. Twenty-two samples of food associated with 15 food poisoning outbreaks and 12 ready-to-serve foods inoculated with approximately 100 C. perfringens spores/g and incubated to simulate improper holding conditions were examined. Alpha-toxin was present in extracts from most of the foods which could be correlated with the viable population as determined by plate counts in sulfite-polymyxin-sulfadiazine (SPS) agar. The amount of α-toxin present could be correlated with previous growth of C. perfringens in food regardless of whether the organisms were viable when the examination was made. This is important because storage and shipment of the food specimens for brief periods at low temperature results in a decrease of 2 to 4 log cycles in the viable plate count in SPS agar, but does not affect the accuracy of estimates of the population level based on the presence of α-toxin.

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