Cat. no. C7740 CRITERION™ m TEC Agar 90.6gm
Cat. no. C7741 CRITERION™ m TEC Agar 500gm
Cat. no. C7742 CRITERION™ m TEC Agar 2kg
Cat. no. C7743 CRITERION™ m TEC Agar 10kg
Cat. no. C7744 CRITERION™ m TEC Agar 50kg


Hardy Diagnostics CRITERION™ m TEC Agar is recommended for use in the enumeration and differentiation of Escherichia coli in water using membrane filtration.

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.


The density of Escherichia coli in water samples has proven to accurately represent the degree of pollution and therefore sanitary quality of ambient, drinking and waste water.(1) Hardy Diagnostics CRITERION™ m TEC (membrane Thermotolerant E. coli) Agar utilizes the nature of coliform bacteria to grow at 44.5ºC (+/- 0.2 degrees).(1) While previous methods of enumeratingE. coli required the use of multiple media types and longer incubation, Dufour et al. produced a membrane filter procedure in 1981 that did not require subculture or further identification of isolates.(2)

This medium selects for and differentiates gram-negative, lactose-fermenting bacteria and allows for the resuscitation of weakened organisms by incubation for 2 hours at 35ºC., before incubation at 44.5ºC. for 18 to 22 hours.(2) If E. coli is present, this results in confirmatory growth at 44.5ºC. suggested by the Standard Methods for the Examination of Water and Wastewater.(1) Since many coliforms may be found occurring naturally from environmental sources, it is recommended that E. coli be used as the indicator for freshwater and marine water testing since it is a known fecal contaminant.(3)

m TEC Agar contains peptones as a source of carbon, nitrogen, vitamins and minerals. Yeast extract supplies complex B vitamins, trace elements and amino acids that help stimulate bacterial growth. Lactose is a carbohydrate that can be fermented by E. coli at elevated temperatures. The buffers in this formula are monopotassium phosphate and dipotassium phosphate. Sodium lauryl sulfate and sodium deoxycholate serve to inhibit gram-positive bacteria. Color indicators are bromcresol purple and bromophenol red; while agar is used to solidify the media.


Gram weight per liter: 45.3gm/L
Lactose 10.0gm
Sodium Chloride 7.5gm
Proteose Peptone No. 3 5.0gm
Potassium Phosphate, dibasic 3.3gm
Yeast Extract 3.0gm
Monopotassium Phosphate 1.0gm
Sodium Lauryl Sulfate 0.2gm
Sodium Deoxycholate 0.1gm
Bromcresol Purple 0.08gm
Bromophenol Red 0.08gm
Agar 15.0gm

Final pH 7.3 +/- 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 grayish-green tan.

Store the prepared culture media at 2-8ºC.



1. Suspend 45.3 gm of the dehydrated culture media in 1 liter of distilled or deionized water. Stir to mix thoroughly.

2. Heat to boiling to dissolve completely. Do not overheat.

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

4. Cool to 45-50ºC and aseptically dispense into petri dishes.


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


Consult references for appropriate water sample size choice to ensure countable plates (20 to 80 colonies per filter) and accurate urea test results.(1)


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


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
MF 20-24 hr 44.5°C Aerobic Growth; yellow to yellow-brown colonies
Enterobacter aerogenes
ATCC ® 13048
MF 20-24 hr 44.5°C Aerobic Inhibited

User Quality Control

Physical Appearance

CRITERION™ m TEC Agar powder should appear homogeneous, free-flowing, and grayish-green tan in color. The prepared media should appear slightly opalescent, deep purple with a red cast, and no precipitates, chips or debris.


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

2. Dufour, A.P. et al. 1981. Membrane filter method for enumerating Escherichia coli. Appl. Environ. Microbiol.; 41(5):1152-1158

3. Geldreich E.E., et al. 1965. Fecal coliform organism medium for the membrane filter technique. J. Am. Water Works Assoc.; 57:208-214.

4. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

5. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

6. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

7. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

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