Chromogenic Coliform Agar is a fast, accurate, and efficient way to detect coliforms and E.coli
during microbiological quality testing of drinking water, disinfected pool water, and treatment plant samples. The guideline, ISO 9308-1:2014 Enumeration of Escherichia coli and coliform bacteria –Part 1: Membrane filtration method for waters with low bacterial background flora, specifies a method based on membrane filtration, subsequent culture on a Chromogenic Coliform Agar medium, and calculation of the number of target organisms in the sample.
Chromogenic Coliform Agar utilizes specific enzymes associated with general coliforms and E.coli for differentiation.
- The chromogen Salmon GAL, when cleaved by D-galactosidase, produces a pink to red coloration; this coloration and enzyme are associated with coliforms.
- E.coli contains D-galactosidase, which cleaves Salmon GAL; however, it also contains D-glucuronidase, which cleaves the chromogen X-glucuronide. The combination of these chromogens produces a dark blue to violet coloration associated with E.coli.
- Tergitol-7 within the medium inhibits Gram positive bacteria and Gram negative bacteria with exception of coliforms.