[Demonstration of staphylococcal thermonuclease from powdered milk]

Demonstration of Staphylococcal Thermonuclease (TNase) from Powder Milk. Some authors have reported that the number of Staphylococcus aureus needed to produce a food-poisoning is 10(6) CFU per gram of food, however, other authors have reported foods without microorganisms but these have produced food-poisoning. Because the methods for staphylococcal enterotoxins demonstration in foods are laborious and expensive procedures, in this paper we tried to demonstrate the thermonuclease (TNase) presence in foods directly, as a helper test for screening foods suspected to be contaminated with this microorganism. To 112 powder milk samples were determined TNase presence by Tatini's et al (1976) and Lachica's (1972) technics, 31 of this samples had S. aureus. Only with Lachica's technique it could be possible to demonstrate TNase in 17 of 112 analyzed samples, 14 of these had viable S. aureus.