The development of chromogenic substrates - a combination of dye and specific enzyme substrates - was a milestone in the development of modern culture media.
The Principle
Chromogenic substrates are colorless and they are stable against pH shift and autoclaving.
Only the characteristic enzyme of a target organism or a target group of organisms can cleave the chromogenic substrate into a sugar part and a chromogen.
In the presence of oxygen this chromogen causes a coloration that concentrates on a typical colony or changes the shade of a broth. The resulting color stays stable for several days, unaffected by the pH, temperature or light. In addition, the coloring does not diffuse into the agar and allows the identification of single colonies.
Advancing Chromogenic Analysis: Merck ChromoCult®
Mixed culture showing
E. coli (blue)/ Coliforms (red)
With its innovative ChromoCult® culture media, Merck has pushed back the boundaries of chromogenic analysis even further: For example since the '90s, Merck's ChromoCult® Coliform Agar allowed the simultaneous detection of Coliforms and
E. coli using a combination of two chromogenic substrates.
Merck was among the first producers of chromogenic media who was able to manufacture this in large quantities with consistently high quality and gave a broad range of users the chance to take part in the advantages.
Use of ChromoCult® media is the colorful way to achieve savings in preparation, incubation, material and labor costs.
Color makes the difference Some chromogenic media are so specific that there is no need to perform additional confirmation steps which also leads to savings of time and money.
