Why chromogenic media?
Chromogenic media represent the biggest step forward in microbiological culture media for a significant period of time. They allow for the isolation and enumeration of micro-organisms based on the presence of specific enzymes in these target micro-organisms. When the target micro-organisms are present, they will produce specific enzymes that are capable of cleaving the chromogenic substrates that have been incorporated into the culture media. These colourless substrates then release a coloured compound that is incorporated into the growing colony turning them a distinctive colour.

In practice, the move from traditional culture media to chromogenic media provides an increase in both the specificity and sensitivity of the isolation method. This increase in specificity, can, in some cases negate the need for sub culture and additional confirmatory tests. This in turn can lead to improved result reporting times and a reduction in consumable costs

A selection of the ready prepared chromogenic media manufactured by SGL includes:

Membrane Lactose Glucuronide Agar (mLGA).
As described in the 2002 Drinking water standards, this chromogenic media allows for the simultaneous detection of both Escherichia coli and other Coliform organisms present in water and related sample types.

Tryptone Bile X-glucuronide Agar (TBX/TBGA).
One of the first chromogenic media to be developed for the isolation of E. coli, this media is based on the formulation of Tryptone Bile Agar with the addition of the X-glucuronide chromogen. E. coli appear as distinctive green/blue colonies on this medium.

Chromogenic Salmonella Agar.
A variety of chromogenic salmonella media are available that will allow for the isolation of both Salmonella typhi and the non-Typhi salmonella from a wide variety of sample types including clinical, food and industrial sample matrices. These media rely on the selectivity of the base media, and in a number of cases multiple chromogen reactions to specifically isolate salmonella if it is present.

For further details on the complete range of ready prepared chromogenic media available from SGL, please contact our Customer Services Department using the contact details at the top of this page.