Coliform Bacteria and Staphylococcus aureus in Retail Natural Cheeses

Abstract

Fifty commercial retail samples of natural cheeses (American and non-American-type) were examined for coliform bacteria, Escherichia coli, E. coli O157:H7, and thermonuclease-positive S. aureus. Nine cheese samples had coliform group bacteria ranging from 10 to 1.1 × 103 CFU/ml by the violet red bile agar procedure. Twenty-four or 48% of the cheeses were positive for coliform group bacteria when a 25-g sample was used in an enrichment broth. One sample had a confirmed E. coli by both the violet red bile agar and enrichment methods. No E. coli O157:H7 were found in the retail natural cheeses examined. Also, no thermonuclease-positive S. aureus were isolated. The levels of potentially pathogenic microorganisms in cheeses were lower in this study than reported in a 1974 to 1976 Canadian study.