Cat. no. C5690 CRITERION™ EC Medium 74gm
Cat. no. C5691 CRITERION™ EC Medium 500gm
Cat. no. C5692 CRITERION™ EC Medium 2kg
Cat. no. C5693 CRITERION™ EC Medium 10kg
Cat. no. C5694 CRITERION™ EC Medium 50kg


Hardy Diagnostics CRITERION™ EC Medium is recommended for the detection of fecal coliforms at 44.5 and 45.5ºC.

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.


Hajna and Perry formulated EC Media for use in the examination of waters, milk, shellfish and other material for evidence of fecal pollution(12) The medium consists of a buffered lactose broth with casein peptone and bile salts.

Lactose in the medium serves as a source of fermentable carbohydrate for the growth of coliforms. Casein peptone provide 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.

Lactose-fermenting microorganisms capable of growing in the presence of the bile salts will ferment lactose resulting in gas production. Gas production is noted by the appearance of bubbles within the durham tube. For the testing of water, wastewater and shellfish, the development of turbidity and gas production within 24 hours at 44.5ºC. indicates the presence of fecal coliforms.(1) When testing food other than shellfish, the development of turbidity and gas production within 48 hours at 45.5ºC. indicates the presence of fecal coliforms.(4) All shellfish isolates require an incubation temperature of 44.5ºC. (rather than 45.5).(4)

The American Public Health Association (APHA) recommends that EC Medium be used in the fecal coliform Most Probable Number (MPN) procedure for the examination of water, wastewater, and foods.(1-3)


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

Final pH 6.9 +/- 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 culture media should be discarded if it is not free-flowing or if the color has changed from its original beige.

Store the prepared culture media at 2-30ºC.



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 tubes containing inverted durham tubes.

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


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K13.


It may be required that further testing be performed for confirmed results.

EC Medium should not be used for the direct isolation of coliforms.

Prior enrichment in a presumptive medium is required for optimal recovery of fecal coliforms when using EC Medium.

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.

Incubation in a waterbath at 44.5 +/- 0.2ºC. is recommended for the detection of fecal coliforms in water and wastewater.

Incubation in a waterbath at 45.5 +/- 0.2ºC. is recommended for the detection of fecal coliforms in foods other than shellfish.

All shellfish isolates require an incubation temperature of 44.5ºC. (rather than 45.5º).(4)


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; turbidity with gas production (bubble in durham tube)
Enterococcus faecalis
ATCC ® 29212
B 24hr 35°C Aerobic Inhibited

User Quality Control


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


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

2. Compendium of Methods for the Microbiological Examination of Foods, 4th ed. 2001. American Public Health Association, 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.

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