Evaluation of staphylococcal thermonuclease (TNase) assay as a means of screening foods for growth of staphylococci and possible enterotoxin production.

Samples of food, naturally and artificially contaminated with Staphylococcus aureus, were analyzed for enterotoxin and thermonuclease (TNase). With the exception of egg, all naturally contaminated foods with detectable amounts of staphylococcal enterotoxin were positive for TNase. The enzyme was also present in the majority of foods with over 1 million S. aureus cells per gram. In artificially contaminated foods. TNase was detected in all samples except egg, acidic foods in which growth of S. aureus was suppressed, and some samples of raw ground beef. Recovery of TNase was influenced by the type of food.