SUMMARY A large batch of enterotoxin A from Staphylococcus aureus strain 196‐E was prepared in easamino acid medium and concentrated 13.5 times by dialysis under polyethylene glycol. Concurrent tests on heat inactivation of this toxin were conducted with monkeys and cats. The heat inactivation curve based on the cat emetic reaction to intraperitoneal injection ean be expressed as a straight‐line semi‐logarithmic curve with a slope (z) of 48° F to traverse one log cycle of time and a resistance at 250°F of 11 min (F49250=11 min). The heat inactivation curve based on the monkey emetic reaction to oral feeding was F49250= 8 min. The heat resistance tests based on the two test animals are in remarkable agreement. Cats were found to be considerably more susceptible to the toxin by injection than were monkeys by feeding. The implication of these tests in relation to heat processing of foods is discussed, and preliminary indications are that the processes given commercially canned foods in which the organisms will grow are sufficient to destroy the toxin.

No abstract

Serological tests were used to determine the slope of the thermal inactivation curve of crude enterotoxin A in Veronal buffer ( p H 7.2), and the resulting z value was 27.8 C. (50 F). Serological assays also showed that the heat inactivation at each time-temperature depended on the original concentration of enterotoxin A. The usefulness of the Oudin tube serological test for determining end points of inactivation of naturally produced enterotoxin A (not concentrated) is discussed. We concluded that this test cannot be used to determine end points of heat inactivation for enterotoxin A in the minute quantities naturally produced in foods.

Electrophoreis of enterotoxin into a middle liquid section of a polyacrylamide gel column enhances recovery for serological assay.