Occurrence of Enterotoxigenic Strains of Staphylococcus aureus and Enterotoxin Production in Bakery Products

Bakery items were surveyed for the presence of Staphylococcus aureus . Items analyzed were oatmeal raisin cookies, apple muffins, cream puffs, and long Johns. S. aureus were isolated from 21 (9.8%) of 214 bakery items surveyed. Enterotoxin was produced by seven of these isolates. An enterotoxin producing S. aureus was found in one apple muffin and one long John and in five of the cream puffs. The pH and water activity ranges for the bakery items would support S. aureus growth except the water activity for the cookies. An enterotoxin A-producing strain of S. aureus was also inoculated in or on the surface of the bakery items. The bakery items were held at 25°C for 48 h to simulate consumer handling. Total S. aureus was determined by plate count on Baird-Parker agar. S. aureus survived on all the bakery items. After 24 h, total cell number decreased on surface inoculated bakery items; however, S. aureus grew well in the inoculated fillings of cream puffs and long Johns increasing to 10⁵ CFU/g.