Cat. no. C7050 CRITERION™ Tergitol 7 Agar 66gm
Cat. no. C7051 CRITERION™ Tergitol 7 Agar 500gm
Cat. no. C7052 CRITERION™ Tergitol 7 Agar 2kg
Cat. no. C7053 CRITERION™ Tergitol 7 Agar 10kg
Cat. no. C7054 CRITERION™ Tergitol 7 Agar 50kg


Hardy Diagnostics CRITERION™ Tergitol 7 Agar is used for enumerating and differentiating coliform bacteria.

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.


Tergitol 7 (sodium heptadecyl sulfate) Agar, or frequently referred to as T7 Agar, is selective for Escherichia coli and members of the coliform group. This medium inhibits the growth of gram-positive microorganisms and spore-forming gram-negative microorganisms, as well as the swarming of Proteus spp., while allowing for superior recovery of coliforms.(4) According to the formula published by Chapman, the addition of Tergitol 7 to an agar medium consisting of proteose peptone No. 3, yeast extract, lactose, and bromothymol blue permitted unrestricted development of all coliform bacteria and inhibited development of gram-negative spore-formers as well as gram-positive microorganisms. He found the difference between Escherichia coli and other coliforms to be distinct on this medium since E. coli produces yellow colonies with yellow halos while other coliforms produce dark red colonies. Bromothymol blue is incorporated as a pH indicator. Counts of coliform organisms on Tergitol 7 Agar plates were found to be as much as 30% higher than on some other selective media.(9)

Chapman modified his original formula by adding 40.0mg of triphenyltetrazolium chloride (TTC) per liter.(5) This medium was found to be helpful in recognizing and identifying Escherichia coli. Confirmation of the presence of E. coli was possible after as little as 10 hours incubation at 35 degrees C. Chapman also reported that Tergitol 7 Agar with added TTC gave a selective medium suitable for the isolation of Candida and other fungi.(5)

Tergitol 7 Agar with TTC was shown to be useful in routine water analysis and the examination of foods.(6,7) The medium conforms with the recommendations of the APHA.(8)


Gram weight per liter: 33.0gm/L
Lactose 10.0gm
Proteose Peptone No. 3 5.0gm
Yeast Extract 3.0gm
Tergitol 7 0.1gm
Bromothymol Blue 0.025gm
Agar 15.0gm

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 33.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

3. Autoclave at 121ºC. for 15 minutes.

4. If desired, cool Tergitol 7 Agar to 50ºC. Add 4ml of either TTC Solution 1% or a filter-sterilized 1% solution of TTC.


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G58.



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 18-48hr 35°C Aerobic Growth; yellow colonies
Enterobacter aerogenes
ATCC ® 13048
A 18-48hr 35°C Aerobic Growth; yellow colonies
Enterococcus faecalis
ATCC ® 29212
B 18-48hr 35°C Aerobic Inhibited; no color change

User Quality Control


CRITERION™ Tergitol 7 Agar powder should appear homogeneous, free-flowing, and beige in color. The prepared media without TTC should appear slightly opalescent, without precipitate, and green in color.


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

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

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

4. Chapman, G.H. 1947. A superior culture medium for the enumeration and differentiation of coliforms. J. Bacteriol.; 53:504.

5. Chapman, G.H. 1951. A culture medium for detecting and confirming Escherichia coli in ten hours. Am. J. Public Health; 41:1381.

6. Kulp, W., et al. 1953. Use of Tergitol 7 Triphenyl Tetrazolium Chloride Agar as the coliform confirmatory medium in routine sanitary water analysis. Am. J. Public Health; 43:1111.

7. Mossel, D.A.A. 1962. An ecological investigation on the usefulness of two specific modifications of Eijkman's test as an element of the methods for the detecting of faecal contamination of foods. J. Appl. Bacteriol.; 25:20.

8. Speck, Marvin L. 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. American Public Health Association, Washington, D.C.

9. MacFaddin, J.F. 1985. Media for Isolation, Cultivation, Identification, Maintenance of Bacteria, Vol. I. Williams & Wilkins, Baltimore, MD.

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