Purpose: RAPID’Enterobacteriaceae is a media for the enumeration of Enterobacteriaceae in food based on the glucose fermentation. The combination of color indicators allows a high level of contrast of Enterobacteriaceae colonies which appear as red on a clear grey medium. A validation based on NF VALIDATION rules and ISO 16140 standard has been conducted using protocols without confirmation and using an automated colony counter providing a direct result in CFU/g.
Methods: In the method comparison study, RAPID’Enterobacteriaceae was compared to the ISO 21528-2 method. Four food categories were tested with two protocols (pour plate method and surface inoculation) and two possibilities of reading (using an automated colony counter or eye reading). Inter-laboratory study was performed by 17 laboratories.
Results: Method comparison results demonstrated there was no significant difference in the linearity, accuracy, specificity and sensitivity of the RAPID’Enterobacteriaceae method when compared to the ISO standard. Inter-laboratory results demonstrated equivalent precision of the two methods, in repeatability and reproducibility conditions and low bias between -0.023 log CFU/g and 0.038 CFU/g.
Significance: The method presented greatly shortens the time to Enterobacteriaceae enumeration by eliminating the need for a confirmation step. The combination of color indicators allows a high level of contrast and ensures an optimal reading. This feature enables the use of an automated colony counter providing a direct result in CFU / g and full traceability for the laboratory.