Which of the following exotoxins is heat-stable?

Staphylococcal enterotoxin is indeed heat-stable, which is a significant characteristic that sets it apart from many other exotoxins. This stability means that the toxin can withstand high temperatures, such as those used in cooking, which allows it to remain active even after food has been heated. This property is a crucial aspect of Staphylococcal food poisoning, as the toxin can be present in improperly stored food and still cause illness after the food is heated.

In contrast, other exotoxins listed, such as cholera toxin, diphtheria toxin, and Shiga toxin, do not possess this level of heat stability. Cholera toxin, while potent, can be inactivated by heat. Diphtheria toxin is also heat-sensitive, making it less stable in high-temperature environments. Shiga toxin, associated with E. coli infections, is not heat-stable either and can be rendered inactive through cooking. Thus, the heat stability of staphylococcal enterotoxin plays a vital role in its pathogenic potential.