HiCrome^™ Coliform Agar

HiCrome^™ Coliform Agar is a selective chromogenic medium recommended for simultaneous detection of Escherichia coli and total coliforms in water and food samples. Sodium lauryl sulfate inhibits gram-positive organisms. The chromogenic mixture contains two chromogenic substrates, Salmon-GAL and X-glucuronide. The enzyme β-D-galactosidase produced by coliforms cleaves Salmon-GAL, resulting in the salmon to red coloration of coliform colonies. The enzyme β-D-glucuronidase produced by E. coli cleaves X-glucuronide. E. coli forms dark blue to violet colored colonies due to cleavage of both Salmon-GAL and X-glucuronide. The addition of tryptophan improves the indole reaction, thereby increasing detection reliability in combination with the two chromogens. To confirm E. coli, add a drop of Kovac′s reagent (Cat. No. 60983) on the dark blue to violet colony. Formation of cherry-red color indicates the positive reaction.

Suspend 27 g in 1 liter distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 121°C for 15 minutes. When a high number of gram-positive accompanying bacteria are expected, add 5 mg/L Novobiocin (Cat. No. 74675) before autoclaving of the medium.

HiCrome is a trademark of HiMedia Laboratories Pvt. Ltd.