Validation of the 3M™ Petrifilm™ Coliform Count Plate for Enumeration of Coliforms in Bottled Water: AOAC Performance Tested Method(SM) 082101

BACKGROUND: The 3M(™) Petrifilm(™) Coliform Count (CC) Plate is a sample-ready-culture medium system which contains modified Violet Red Bile nutrients, a cold-water-soluble gelling agent, and a tetrazolium indicator that facilitates colony enumeration. OBJECTIVE: To validate the 3M Petrifilm CC Plate method for bottled water through the AOAC(®) Performance Tested Method(s)(SM) program. METHODS: The performance of the 3M Petrifilm CC Plate was compared to the U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 4, Section III.D for the enumeration of coliforms in bottled water. Matrix data were normalized by log(10) transformation and performance indicators included repeatability and difference of means with 90 and 95% confidence intervals. Inclusivity, exclusivity, robustness, and product consistency and stability were evaluated. RESULTS: This study demonstrated that the 3M Petrifilm CC Plate method detects and enumerates coliforms from bottled water. The average log(10) counts of the 3M Petrifilm CC Plate method were equivalent to or better than the average log(10) counts of the reference method. Results from inclusivity and exclusivity studies demonstrated that the 3M Petrifilm CC Plate method differentiated coliforms from non-coliform strains. In product consistency, stability, and robustness testing, different lots of 3M Petrifilm CC Plates and small deviations in incubation time and temperature did not affect test results. CONCLUSION: The 3M Petrifilm CC Plate method is an accurate and robust method for the enumeration of coliforms in bottled water. HIGHLIGHTS: The 3M Petrifilm CC Plate allows for detection of confirmed coliforms within 24 h. Up to 20 sample-ready plates can be stacked during incubation, providing flexibility and saving space.