Cat. no. C5990 CRITERION™ Lauryl Tryptose Broth with MUG 71.4gm
Cat. no. C5991 CRITERION™ Lauryl Tryptose Broth with MUG 500gm
Cat. no. C5992 CRITERION™ Lauryl Tryptose Broth with MUG 2kg
Cat. no. C5993 CRITERION™ Lauryl Tryptose Broth with MUG 10kg
Cat. no. C5994 CRITERION™ Lauryl Tryptose Broth with MUG 50kg


Hardy Diagnostics CRITERION™ Lauryl Tryptose Broth with MUG is recommended as a test of Escherichia coli and other coliforms in water and sewage.(6) It is also used as a confirmatory test of lactose-fermentation with gas production for milk and the detection of coliforms in foods by fluorogenic means.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.


Lauryl Tryptose Broth with MUG was formulated after Mallman and Darby for detection of coliform bacteria in water.(7) This is a selective medium because it contains sodium lauryl sulfate which inhibits gram-positive microorganisms.

Lactose provides fermentable carbohydrate for the growth of coliforms. Casein peptone provides a source of nutrients. Sodium chloride serves as an inhibitory agent toward gram-positive cocci and spore-formers, particularly fecal streptococci and bacilli. The pH of the medium is maintained by the presence of a strong potassium buffering system. The presence of phosphate buffer ensures rapid growth and increased gas production; even of slow lactose-fermenting coliforms.

The addition of MUG, a fluorogenic substrate, allows for the rapid detection of coliforms when the medium is observed for fluorescence using a long-wave (366nm) UV light source. It can also detect anaerogenic E. coli strains. Most strains of E. coli produce beta-glucuronidase which hydrolyzes MUG to the fluorogenic compound 4-methyl-umbelliferone. Studies by Feng and Hartman noted that most E. coli strains (96%) and all enterotoxigenic E. coli strains (100%) and a moderate number of Salmonella (17%) and Shigella (40%) strains produce beta-glucuronidase.(8) False-positives can also be caused by Streptococcus spp.


Gram weight per liter: 35.7gm/L
Tryptose 20.0gm
Lactose 5.0gm
Sodium Chloride 5.0gm
Dipotassium Phosphate 2.75gm
Monopotassium Phosphate 2.75gm
Sodium Lauryl Sulfate 100.0mg
4-Methylumbelliferyl-beta-D-Glucuronide 50.0mg

Final pH 6.8 +/- 0.2 at 25ºC.

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


Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated media should be discarded if it is not free-flowing or if the color has changed from its original light beige.

Store prepared medium at 2-8ºC.



1. Suspend 35.7gm of the dehydrated culture media in 1 liter of distilled or deionized water. If evaluating 10ml samples, prepare as double strength broth (71.4gm/L).

2. Distribute into test tubes containing inverted durham tubes.

3. Sterilize in the autoclave at 121ºC. for 15 minutes.


For information on procedures and interpretation of results, consult listed references.


It may be necessary to invert the tube prior to inoculation if bubbles are trapped in the durham tube. Trapped bubbles that are not released may lead to false-positive results.

Turbidity alone is not indicative of a positive test for the presence of coliforms; turbidity with gas production is considered a positive test.

Some strains of Shigella and Salmonella produce beta-glucuronidase which may result in false interpretation of test results.

The presence of streptococci in the test sample may lead to false-positive results.

Some foods, such as shellfish, contain natural GUD activity. In these instances, a tube of LST Broth is inoculated and incubated for 24 hours in the usual manner, and then all growth-positive tubes are subjected to a confirmatory 24 hour EC test using EC Medium with MUG (EC Medium that contains 50ug MUG/ml).


Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Growth; fluorescence under long-wave UV light source, turbidity with gas production
Klebsiella pneumoniae
ATCC ® 13883
A 24hr 35°C Aerobic Growth; turbidity with gas production, no fluorescence
Shigella flexneri
ATCC ® 12022
A 24hr 35°C Aerobic Growth; turbidity without gas production, no fluorescence
Staphylococcus aureus
ATCC ® 25923
B 24hr 35°C Aerobic Partial to complete inhibition; turbidity without gas production, no fluorescence

User Quality Control


CRITERION™ Lauryl Tryptose Broth with MUG powder should appear homogeneous, free-flowing, and light beige in color. The prepared media should appear clear, and amber in color.


1. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

2. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

3. Bacteriological Analytical Manual (BAM), 8th ed. Revision A 1998. Association of Official Analytical Chemists International, Gaithersburg, MD.

4. Association of Official Analytical Chemists. Official Methods of Analysissm, AOAC, Washington, D.C.

5. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

6.American Public Health Association. Standard Methods for the Examination of Water and Wastewater, APHA, Washington, D.C.

7. Mallman, W.L. and Darby, C.W. 1941. Uses of a Lauryl Sulfate Tryptose Broth for the detection of coliform organisms. Am. J. Pub. Health; 31:127.

8. Appl. and Env. Microb.; 48:285, 1984.

ATCC is a registered trademark of the American Type Culture Collection.