The RAPID’E.coli 2 protocol allows the enumeration and differentiation of E. coli and other Coliform bacteria in a single chromogenic agar plate and in less than 24 hours without any confirmation. The method has been recently validated by Health Canada.
Purpose: The objective of this study is to summarize the performance evaluation did in order to obtain the Health Canada approbation for publication in Compendium of Analytical Methods .
Methods: The evaluation has been conducted through two sets of results coming from AOAC Performance-Tested Method 050601 and AFNOR validated protocol BRD 07/08-12/04, BRD 07/07-12/04, BRD 07/01-07/93. The RAPID’E.coli 2 protocol has been compared to the reference method AOAC 966.24, ISO 16649-2 and ISO 4831. The inclusivity was tested using 108 isolates of E. coli (60) and non-E. coli coliform bacteria (48) and the exclusivity was tested using 32 non-coliform bacteria. A Method Comparison Study was conducted on several food categories using three inoculation levels using naturally contaminated products and artificial contamination. An Inter-Laboratory Study was run involving 10 laboratories.
Results: RAPID’E.coli 2 agar yielded an inclusivity rate of 99% and an exclusivity rate of 94%. For E. coli, the critical Level, limit of detection and limit of quantification determined during the method comparison study were 2.97, 4.58 and 12.93 CFU/ml respectively and for other coliforms 3.47, 5.94 and 13.43 CFU/ml respectively.
Significance: RAPID’E.coli 2 was shown to be an effective and efficient method for enumeration of E. coli and coliforms in only 24 h.