ChromaticTM Coli Coliform Chromogenic Medium is a high-quality product designed for the detection and enumeration of Escherichia coli and coliform bacteria in food and water samples. Thanks to its selective formulation, this medium makes it possible to effectively identify the microorganisms present, facilitating microbiological analysis in laboratories and quality control facilities.

Product Features

• Format: 20 plates of 90 mm


• Type of medium: Chromogenic and selective


• Use: Microbiological analysis of food and water

Medium Composition

The typical formulation of the medium is composed of:

• Peptone: 15.0 g/l - source of amino acids and essential nutrients


• Yeast Extract: 3.0 g/l - rich in B vitamins


• Sodium Chloride: 5.0 g/l - maintains osmotic balance


• Chromogenic and Selective Mixture: 1.7 g/l - for colorimetric identification of microorganisms


• Agar: 15.0 g/l - solidifying agent

Final pH: 7.2 ± 0.2 at 25°C

Method Principle

The Chromogenic Medium works thanks to a selective inhibition mechanism, which allows the growth of E. coli and coliform bacteria while hindering the proliferation of most Gram-positive bacteria. The colonies of E. coli appear green, while the other coliform bacteria take on a mauve coloration.

Medium Preparation

Preparing the medium is simple and requires the following steps:

• For the dehydrated medium: suspend 39.7 g of powder in 1 liter of sterile distilled or deionized water.


• Mix well and heat until completely dissolved (do not autoclave).


• For the medium in bottles: dissolve the contents in a water bath at 100°C until completely dissolved.


• Pour into Petri dishes under aseptic conditions after cooling to 45-50°C.

Test Procedure

To test samples, follow these instructions:

• Inoculate solid samples directly onto the surface of the medium.


• Inoculate liquid samples by spreading or using membrane filtration technique.


• Incubate at 35 ± 2°C for 18-24 hours in an aerobic atmosphere.

Interpretation of Results

After incubation, observe the color and morphology of the colonies. The results can be interpreted as follows:

*Note: E. coli ß-glucuronidase-negative strains, such as E. coli O157, are colorless on this medium.

Advantages of Use

• Rapid and accurate identification of E. coli and coliform bacteria.


• Ease of preparation and use.


• Suitable for analyses in food and quality control laboratories.

The ChromaticTM Coli Coliform Chromogenic Medium is an indispensable ally for ensuring food safety and water quality, providing reliable and timely results.