Growth of enterotoxigenic Staphylococcus aureus type A and its potentially toxin production in salted cheese whey

Growth of Staphylococcus aureus strain No 743 and its production of entero- toxin A (ent. A), thermonuclease (TNase) and ß-hemolysin were studied in cheese whey containing zero, 5, 10, 15, and 20% salt during incubation at 37°C for 48 h. Results revealed that the concentration of salt less than 10% promotes S. aureus growth and production of ent. A, TNase and ß-hemolysin. In the presence of high concentrations of salt (15-20%), growth was inhibited and ent. A production was incompletely repressed, while TNase and ß-hemolysin activities were completely inhibited. It is concluded that using unsalted or salted cheese whey containing S. aureus in preparing any other kind of food related commodity is dangerous. Furthermore, TNase and ß-hemolysis tests are unreliable as indicators for tracing enterotoxin A in dairy products containing more than 10% salt.