CRITERION™ EC MEDIUM WITH MUG

Cat. no. C5680 CRITERION™ EC Medium with MUG 74gm
Cat. no. C5681 CRITERION™ EC Medium with MUG 500gm
Cat. no. C5682 CRITERION™ EC Medium with MUG 2kg
Cat. no. C5683 CRITERION™ EC Medium with MUG 10kg
Cat. no. C5684 CRITERION™ EC Medium with MUG 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ EC Medium with MUG is recommended for the detection of Escherichia coli in water and food samples 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.

SUMMARY

EC Medium with MUG is composed of the same basal formula as EC Medium developed by Hajna and Perry, with the addition of 4-methylumbelliferyl-beta-D-glucuronide (MUG).(8) The medium consists of a buffered lactose broth with pancreatic digest of casein, bile salts, and MUG.

Lactose provides fermentable carbohydrate for the growth of coliforms. Pancreatic digest of casein provides a source of nutrients. The bile salts serve as inhibitory agents 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 addition of MUG, a fluorogenic compound, allows for the rapid detection of E. coli when the medium is observed for fluorescence using a long-wave (366nm) UV light source.(7,9) Anaerogenic strains of E. coli can also be detected through the use of MUG.(7)

The detection of E. coli with MUG is based on the ability of beta-glucuronidase, an enzyme possessed by most E. coli strains, to hydrolyze 4-methylumbelliferyl-beta-D-glucuronide. Once hydrolyzed, the substrate yields 4-methylumbelliferone, a fluorescent end product.(7,9) Development of fluorescence allows the detection of E. coli in pure or mixed cultures within 4-24 hours following inoculation and incubation of EC Medium with MUG.

Studies conducted by Feng and Hartman revealed beta-glucuronidase activity in 96% of E. coli, 100% of enterotoxigenic E. coli, 17% Salmonella spp. and 40% of Shigella spp.(7)

EC Medium with MUG is recommended by the American Public Health Association (APHA) for the detection and enumeration of coliform organisms in foods, waters and wastewaters.(1,2)

FORMULA

Gram weight per liter: 37.0gm/L
Pancreatic Digest of Casein 20.0gm
Lactose 5.0gm
Sodium Chloride 5.0gm
Dipotassium Phosphate 4.0gm
Monopotassium Phosphate 1.5gm
Bile Salts No. 3 1.5gm
MUG 50.0mg

Final pH 6.9 +/- 0.2 at 25ºC.

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

STORAGE AND SHELF LIFE

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 culture media should be discarded if it is not free-flowing or if the color has changed from its original light beige.

Store the prepared culture media at 2-30ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 37.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Warm slightly to dissolve completely.

3. Dispense into test tubes containing inverted fermentation vials (durham tubes).

4. Autoclave at 121ºC. for 15 minutes.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K64.

LIMITATIONS

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. Fluorescence may be observed in anaerogenic E. coli.

Strains of E. coli that fail to grow in EC Medium with MUG, fail to produce gas, or fail to produce glucuronidase may infrequently be encountered.

Strains of Salmonella, Shigella, and Yersinia that produce glucuronidase may be encountered. These strains must be distinguished from E. coli on the basis of other parameters, i.e., gas production, growth at 44.5ºC.

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

False-positive results may occur when testing oysters. Oysters produce glucuronidase which interferes with the accuracy of the assay. When testing oyster samples, it is recommended that an enrichment step in Lauryl Sulfate Broth be performed prior to inoculation of the test sample to EC Medium with MUG. The preenrichment step dilutes the glucuronidase from the oysters and decreases the possibility of false-positive results.

MATERIALS REQUIRED BUT NOT PROVIDED

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

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Growth; turbidity with gas production and fluorescence under a long-wave UV light source
Enterobacter aerogenes
ATCC ® 13048
A 24hr 35°C Aerobic Growth; turbidity with gas production, without fluorescence
Enterococcus faecalis
ATCC ® 29212
B 24hr 35°C Aerobic Inhibited

User Quality Control

PHYSICAL APPEARANCE

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

REFERENCES

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

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

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

4. Bacteriological Analytical Manual (BAM), 2002. Association of Official Analytical Chemists International, Gaithersburg, MD.

5. Official Methods of Analysis of the Association of Official Analytical Chemists, 15th ed. 1990. AOAC, Arlington, VA.

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

7. Feng and Hartman. 1982. Appl. Environ. Microbiol.; 43:1320.

8. Hajna and Perry. 1943. Am. J. Public Health; 33:550.

9. Robison. 1984. Appl. Environ. Microbiol.; 48:285.

10. Federal Register. 1991. National primary drinking water regulation; analytical techniques; coliform bacteria. Fed Regist.; 56:636-643.


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

052316gr