Survival of Enteropathogenic and Non-Pathogenic Escherichia coli During the Manufacture of Camembert Cheese.

Camembert cheese was manufactured from milk contaminated with pathogenic and nonpathogenic strains of Escherichia coli . E. coli was enumerated using Violet Red Bile Agar (VRB) pour plates, a most probable number method, and surface plating on Trypticase Soy Agar (TSA) plates followed by an overlay of VRB (TSA + VRB). Numbers of E. coli during cheese manufacture increased about two log cycles during the first 6 h, then decreased during the initial stages of ripening with some strains disappearing from the cheese within the first 2 weeks of ripening, and other strains surviving 4 to 6 weeks. The rate of inactivation of E. coli in the cheese decreased as the cheese ripened and the pH increased. No growth of E. coli was observed in ripe cheese at a pH of 6.7, however rapid growth of E. coli occurred on the surface of the cheese. The TSA + VRB method was acceptable for enumeration of E. coli in Camembert cheese.