Behavior of Enteropathogenic Escherichia coli During Manufacture and Ripening of Brick Cheese

Abstract

The ability of enteropathogenic Escherichia coli (EEC) to grow and survive during the manufacture and ripening of brick cheese was determined. Pasteurized milk artificially contaminated with EEC was used to make cheese by the washed-curd method. EEC was enumerated by surface plating samples on Trypticase Soy Agar (TSA) with an overlay of Violet Red Bile Agar (VRB), and by using VRB Agar pour plates. EEC increased 1000-fold during the manufacturing process and numbers decreased slowly during ripening while the smear developed and during refrigerated storage of cheese. Seven weeks after manufacture, numbers of EEC in cheese ranged from 700 to 20,000/g with initial contamination of milk at about 500/ml. Limited growth of EEC on the surface of brick cheese occurred during ripening and these bacteria were inactivated slowly during storage. Counts of EEC obtained with VRB Agar pour plates were 6–59% as large as counts obtained using TSA surface plating with VRB Agar overlay.