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EC BROTH with MUG

CODE: CM0979

A selective broth for the growth of coliforms and Escherichia coli from food and environmental samples.

Directions
Suspend 37g of EC Broth with MUG in 1 litre of distilled water. Mix well to dissolve and distribute into final containers containing inverted Durham tubes. Sterilise by autoclaving at 121° C for 15 minutes.

Description
Escherichia coli is a common Gram-negative micro-organism which may be present in food, water and environmental samples. Owing to its importance as an indicator of faecal contamination, continuing efforts have been put into developing rapid and specific methods for its identification.

The finding of a highly specific enzyme of Escherichia coli, beta-glucuronidase, has offered a range of opportunities for the improvement of culture media for the identification of this organism. Numerous studies have confirmed a beta-glucuronidase-positive reaction in the middle to upper 90% range of Escherichia coli isolated from a variety of sources¹. The highly sensitive substrate 4-methylumbelliferyl-ß-D-glucuronide (MUG) is cleaved by the enzyme and the hydrolisis product 4-methylumbelliferone shows a visible green/blue fluorescence under long-wave ultra-violet light (366nm).

EC Broth with MUG contains 4-methyl-ß-D glucuronide which is cleaved by the enzyme glucuronidase (GUD) produced by Escherichia coli resulting in a fluorescent end-product. This medium is recommended by FDA/BAM² for the confirmation of Escherichia coli from shellfish and meats. For other details regarding the formulation of EC broth with MUG please refer to EC Broth (CM0853).

NaOH addition generally improves fluorescence by increasing the alkalinity of the solution. An increase in fluorescence can also be achieved by increasing the level of MUG added to the base medium.

Technique
Perform the MPN presumptive and confirmed test for faecal coliforms in shellfish. Transfer one loopful from the positive cultures into tubes of EC broth with MUG. Incubate at 44.5°C for 22-26 hours. Examine the tubes growth and gas production and for fluorescence (using long wave (365nm) UV light).

For full details of the method please refer to the FDA/BAM standard methods.

Storage conditions and Shelf Life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Appearance
Dehydrated medium: Straw coloured, free flowing powder
Prepared medium: Straw coloured solution

Quality control

*This organism is available as a Culti-Loop®

Precautions
Ensure that the glass tubes used for the preparation of the medium do not auto fluoresce and take the relevant safety precautions when using a UV lamp.
Some pathogenic strains, typically Escherichia coli O157:H7 are usually glucuronidase negative and therefore will not give a positive result in this test.
Other enteric organisms e.g. some Shigella species are also glucuronidase positive.

References
1.Frampton, E. W. and Restaino, L. (1993) J. Appl. Bact. 74, 223-233.
2. "Association of Official Analytical Chemists" F.D.A. Bacteriological Analytical Manual 8th Edition (1995) AOAC, Arlington Va.