Clinical Microbiology


CHROMagar™ O157

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Packaging / Colonies appearance

For the selective isolation and differentiation
of E. coli O157 in food and animal samples.

Typical Appearance of microrganisms

E. coli O157 → mauve
Other bacteria → steel blue, colourless or inhibited

Order References 

Please use these references when
contacting your local distributor:

5000 mL ..........EE222
25 L..................EE223-25

To download the certificate of analysis, please indicate your lot number below :


Medium Performance

  1. Easier detection: E. coli O157 is detected by a characteristic mauve colour after only 18 h of incubation, while most other E. coli are blue.

  2. Higher specificity of CHROMagar™ E.coli O157 compared to SMAC:
    The conventional medium for the detection of E. coli O157 is Sorbitol MacConkey (SMAC) Agar, which has very poor specificity, thus exhibiting an abundance of false positives (Proteus, E. hermanii, etc.). Sorbitol Mac Conkey is also difficult to read because there is a change of colouration in the case of prolonged incubation.
    High Sensitivity:
    E. coli O157 → 89 %*

*Sensitivity from scientific study: K.A. Bettelheim, 1998. Reliability of CHROMagar O157 for the detection of enterohaemorrhagic E. coli (EHEC) O157 but not EHEC belonging to other serogroups. J.Appl.Microbiol.85:425-428.

Medium Description

Gain flexibility using powder rather than ready to use plates: Use the entire pack, or, just a portion if there is a need for a smaller number of plates. If kept under appropriate storage temperature, CHROMagarTM E.coli O157 has a more than 18 months shelf life. This flexibility is essential to avoid the waste resulting from expired-unused plates. 

-Referenced in the Chinese Standard for microbiological examination of food hygiene GB/T 4789.36-2008.
-USDA SOP No.: MDP-QA-03 (Page 1 of 6 Title: Quality Assurance (QA) Controls Revision: 06 Replaces: 04/01/09 Effective: 09/25/09, United States Department of Agriculture,Agricultural Marketing Service, Science & Technology, Microbiological Data Program)

Please refer to our notice and Material Safety data sheet for complete information about the medium.
CHROMagar™, Rambach™, AquaCHROM™ are trademarks created by Dr. A. Rambach.

Last Update: 21-May-2019

Focus on E. coli O157

Escherichia coli (E. coli) are bacteria commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless. Some strains, however, such as Verocytotoxigenic E. coli (VTEC), also known as Shigatoxigenic E. coli (STEC) can cause severe foodborne diseases. Enterohaemorrhagic E. coli (EHEC) are a subset of VTEC, which can cause severe disease in humans such as Haemolytic Uraemic Syndrome (HUS). VTEC have been isolated from the gut contents of many animals, including cattle and sheep. VTEC are mainly transmitted to humans primarily through consumption of contaminated foods, but can also be transmitted through handling animals carrying these bacteria.

E. coli O157 Epidemiologic Issues

The E. coli serotype O157:H7 or its non-motile variant O157:H- is the most common VTEC serotype in relation to public health. Its significance was recognized in 1982, following two outbreaks in the USA. Since then, more than 180 outbreaks have been reported worldwide, with an estimated W.H.O figure of 70,000 infections per year.
As typical VTEC, E. coli O157 are naturally found in the intestinal contents of livestock, especially cattle and sheep. Their presence in these animals’ faeces makes them an important source of food and water contamination.


Outbreak investigation: STEC O157


Publication: Medical Laboratory Observer Author: Durso, Lisa Date published: March 1, 2010 Extracted from

Shiga-toxigenic Escherichia coli O157 and non-Shiga-toxigenic E. coli O157 respond differently to culture and isolation from naturally contaminated bovine faeces


L.M. Durso and J.E. Keen USDA, ARS, US Meat Animal Research Center, Clay Center, NE, USA Publication : Journal of Applied Microbiology ISSN 1364-5072 2007

Isolation of vero cytotoxin-producing Escherichia coli O157 from wild birds.


Wallace J.S. et al. 1997.
Journal of Applied Microbiology,
82 : 399-404.

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