Examination of Large Quantities of Cheese for Staphylococcal Enterotoxin A

Abstract

A serological test for staphylococcal enterotoxin, using a microslide gel diffusion technique, was employed to examine 4.07 million pounds of cheese suspected of containing staphylococcal enterotoxin A. The sensitivity of the microslide gel diffusion method was determined with purified enterotoxin A. A concentration of 0.4 ~g/ml of enterotoxin A was detected by this technique. The procedure of extraction and concentration of the enterotoxin in cheese permitted the detection of 0.3 t~g of enterotoxin A per 100 g cheese, with a recovery of 16 to 35%. To test 4.07 million pounds of cheese, each of ten persons was trained to do a specific portion of the method. Testing of 24 to 40 samples was initiated daily and samples in process were continued to completion. Eight to ten days elapsed from the start to the completion of analysis of a sample. Of tile 2,112 vats of cheese tested, 59 were found to be toxic. One of the more toxic vats contained approximately 12 tLg of enterotoxin A per 100 g of cheese. The vats of cheese found to be toxin-free were released and consumed with no reported illness.