E.Coli O157:H7 Chromogenic Medium is used for rapid detection of E.Coli O157: H7 in food and Patient faecal samples. 

The colonies are brilliant red, pink or red, no blue halo around, Escherichia coli and coliform are dark blue, blue or purple, blue halos around the colonies; the other are blue, yellow or colorless.

The high specificity of the medium, can overcome the false positive and false negative results caused by SMAC medium, it is an ideal medium for rapid detection.

Ingredients (g/L):

*Adjusted and/or supplemented as required to meet performance criteria.

Directions:

Suspend 17.2g of the medium in 200mL of distilled water, heat about 2 minutes, add a piece of CT additive when cooling down to 45-50℃, mix thoroughly, pour into petri dishes.

Warning: Prepared medium must be kept dry, can place inverted culture in incubator at 36 ± 1 ℃ for 1-2 hours.

Procedures:

1. Prepared sample solution according to national standards, SN standard, FDA standards or other methods.

2. Transfer 25g sample solution into 225mL mEC Broth or mTSB broth, enrichment culture for 18- 24hours at 36 ± 1 ℃;

3. Take one ring enrichment broth with a 3mm inoculation loop, streak to inoculated on O157 chromogenic medium, make two plates

4. The colonies are brilliant red, pink or red, no blue halo around, Escherichia coli and coliform are dark blue, blue or purple, blue halos around the colonies; the other are blue, yellow or colorless.

5.  For typical colonies, do O157:H7 serological test and biochemical tests.

Note: The results must be judged within 24 hours at 36 ± 1 ℃, in case that the color of color changes.

Quality Control:

1. Appearance:

The dehydrate powder medium is homogeneous, having good flowability, grey white, prepared medium is blue solid.

2. Microbial sensitivity test:

Incubated at 36 ± 1 ℃ 18-24h:

Methods limitations:

The typical E.Coli O157:H7 on the medium must be do serological test and biochemical tests

Typical features:

The colonies of E.Coli are brilliant red, pink or red, no blue halo around, Escherichia coli and coliform are dark blue, blue or purple, blue halos around the colonies; the other are blue, yellow or colorless.

        E Coli O157：H7 ATCC35150                    E Coli O157：H7 ATCC43888

Storage:

The prepared plates can be kept for 2-5 days, avoid direct exposure to light. The powder medium should be placed in a dark, dry place, storage temperature 2-8 ℃, avoid direct exposure to light.

Failure:

Dry powder media which are over the shelf life, caking and color variation cannot be used.

Note:

This medium is only for laboratory use.

Reference:

1、Rappaport, F., and E. Henig. 1952. Media for the isolation and differentiation of pathogenic Escherichia coli (serotypes 0111 and 055). J. Clin. Pathol. 5:361-362.

22. U.S. Food and Drug Administration. 1995. Bacteriological analytical manual, 8 th ed., AOAC International, Gaithersburg, MD.