Oxoid CM1046B Kemasan 500 gram Detect and enumerate Escherichia coli and other coliforms in food and water samples with selective, chromogenic Thermo Scientific Brilliance E. coli / Coliform Selective Agar. The agar base uses two chromogens to differentiate between Escherichia coli and other coliforms. This results in purple E. coli, as they are able to cleave both chromogens while other coliforms, giving pink colonies.