RAPID’E.coli 2 agar, manufactured by Bio-Rad Laboratories, was granted Performance Tested Method status by the AOAC Research Institute (certificate # 050601). RAPID’E.coli 2 is a chromogenic medium for detection and enumeration of E. coli and other coliform bacteria in food in 24 hours. It is a rapid method producing accurate and easy-to-read results. Current methods for enumeration of E. coli and coliform bacteria can be costly and laborious. The use of chromogenic substrates in media has lead to development of faster and easier methods for detection, differentiation and enumeration of target bacteria.

RAPID’E.coli 2 is validated for enumeration of E. coli and other coliform bacteria in raw ground beef, raw boneless pork, fermented sausage, processed ham, processed turkey, frozen turkey breast, raw ground chicken, cottage cheese, processed ricotta cheese, unpasteurized raw milk, and dry infant formula. It is validated at two incubation temperatures, 37°C and 44°C (cottage cheese and processed ricotta cheese are only validated at 37°C only).

The principle of RAPID’E.coli 2 medium relies on simultaneous detection of two enzymatic activities, Beta-D-Glucuronidase (GLUC) and Beta-DGalactosidase (GAL). The medium contains two chromogenic substrates. One substrate is specific to GAL and results in blue green coloration of colonies positive for this enzyme and one substrate is specific to GLUC and results in violet coloration of colonies positive for this enzyme.

Coliforms, other than E. coli, (GAL+/GLUC-) form blue to green colonies while, specifically, E. coli (GAL+/GLUC+) form violet colonies. A count of total coliforms can be obtained by adding the number of blue colonies and the number of violet colonies. Differentiation of coliforms and specifically E. coli is carried out by observing a simple color change reaction. Observation of gas bubbles for differentiation is not necessary.

RAPID’E.coli 2 is available in two formats, dehydrated media (Item # 356- 4024) or ready-to-use bottled media (Item # 355-5299).