Heat Inactivation of Staphylococcal Enterotoxin A

Abstract

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.

Short communication: Pasteurization as a means of inactivating staphylococcal enterotoxins A, B, and C in milk

“…At temperatures above 100°C, Denny et al (1966) noted that SEA at a concentration of 7 μg/mL gave heat inactivation end points of 8 to 11 min at 121.1°C, as compared with 22 min at 121.1°C at an enterotoxin concentration of 21 μg/mL. Intravenous injection of enterotoxin B heated at 115.6°C for 32.5 min and longer did not induce an emetic response in cats (Read and Bradshaw, 1966).…”

The formation ofStaphylococcus aureusenterotoxin in food environments and advances in risk assessment

“…They are most commonly described as very stable, and are resistant to heat as well as degrading enzymes. 15,41,42 However, some cases have been reported where the toxins disappeared. Recently, SEA and SED were found to decrease in boiled ham after a period of accumulation, 7,8 and a number of earlier studies have reported the disappearance of SEA in broth, minced food and raw and pasteurized milk.…”

Micro‐organisms in dried foods: their significance, limitation and enumeration*

“…During the process of milk concentration, the prevailing conditions of reduced water activity (aw) allow Staphylococcus aureus to grow in the absence of competition (Mossel, 1975b). In the subsequent drying process the bacterial cells are killed but the preformed heat stable toxins remain unaffected (Anderson & Stone, 1955;Denny, Ran & Bohrer, 1966;Read & Bradshaw, 1966;Denny, Humber & Bohrer, 1971;Fung et al, 1973). Similar conditions for the uninhibited outgrowth of S. aureus can also occur during the manufacture of pasta products where a drying temperature of 45°C and a gradual decrease of water activity are involved (Mossel, 1975a).…”