Part of Thermo Fisher Scientific

Thermo Scentific

Dehydrated Culture Media


CODE: CM0980

for the presumptive identification of E. coli

Typical Formula*






Di-potassium hydrogen phosphate


Potassium dihydrogen phosphate


Sodium chloride


Sodium lauryl sulphate


4-methylumbelliferyl-b-D-glucuronide (MUG)


pH 6.8 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards

Suspend 35.65g of Lauryl Tryptose Broth with MUG in 1 litre of distilled water. Warm to 40°C. Mix well to dissolve and distribute into final containers holding inverted Durham tubes. (Please be aware of the special glassware requirements when using ultra-violet light.). Sterilise by autoclaving at 121° C for 15 minutes.

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 feacal 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 oppertunities 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-methylumbellifery-ß-D-glucuronide (MUG) is cleaved by the enzyme and the hydrolysis product 4-methylumbelliferone shows a visible green/blue fluorescence under long-wave ultra-violet light. (366nm).

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.

Lauryl Tryptose Broth provides a selective medium which is used for the detection of coliform organisms in water, dairy products and other foods and with the addition of MUG is a Standard Methods medium recommended by FDA/BAM2.

Lauryl Tryptose Broth was designed to promote a rich growth and copious gas production from small inocula of coliform organisms. Aerobic sporing bacteria are completely inhibited. The advantage in using this product is that in addition to giving the fermentation reaction typical of MacConkey Broth it can also be directly tested for the presence of indole. Unlike MacConkey Broth, the medium contains no indicator, but this can be added (if required) after incubation.

The use of MUG in a Most Probable Number (MPN) technique for enumeration of presumptive Escherichia coli in milk and milk products has been specified in a standard ISO procedure. For further information about MUG see MUG Reagent BR0071 under Biological Reagents.

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 room temperature.

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

Quality control

Positive control:

Expected result at 35°C

Escherichia coli ATCC® 25922 *

Turbid growth, gas, fluorescence

Negative control:


Staphylococcus aureus ATCC® 25923*

Inhibited or no growth, no gas, no fluorescence

* This organism is available as a Culti-Loop®

.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.

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