Cat. no. G115 Tryptone Glucose Extract Agar, 15x100mm Plate, 18ml 10 plates/bag


Hardy Diagnostics Tryptone Glucose Extract Agar is recommended for the cultivation and enumeration of microorganisms found in food, water, and dairy products.

This product is not intended to be used for the diagnosis of human disease.


In 1910, The American Public Health Association (APHA) issued its first publication entitled " Standard Methods of Milk Analysis ," which recommended the use of Standard Nutrient Agar for estimating bacterial counts in milk and dairy products. (12) In 1935, Bower and Hucker outlined the composition of a medium for the bacteriological analysis of milk, and reported higher plate counts and larger colony sizes from routine milk grading laboratories. (1,2) Consequently, many researchers compared the performance of this medium, Tryptone Glucose Skim Milk Agar, to the more commonly used Nutrient Agar for estimating bacteria in milk samples and other dairy products.

In 1948, the American Public Health Association (APHA) adopted Tryptone Glucose Extract Agar for use in testing milk and dairy products; for many years, this medium became the standard for testing dairy and water products when supplemented with milk. (4) Tryptone Glucose Extract Agar is currently recommended by the Compendium of Methods for the Microbiological Examination of Foods for performing the heterotrophic plate count when testing bottled
water. (5)

Hardy Diagnostics Tryptone Glucose Extract Agar is a non-selective medium containing pancreatic digest of casein, beef extract, and glucose, which provide vital amino acids, nitrogen, carbon compounds, carbohydrates, essential minerals, and trace substances to promote the growth of a variety of microorganisms. Agar is the solidifying agent.


Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 5.0gm
Beef Extract 3.0gm
Glucose 1.0gm
Agar 15.0gm

Final pH 7.0 +/- 0.3 at 25ºC.

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


Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.



Specimen Collection: Consult listed references for information on specimen collection and processing of food, dairy, water samples, and other materials of sanitary significance. (1-8,10,11)

Prior to inoculation, warm prepared media to room temperature.

Spread Plate Method:

1. Prepare serial dilutions in sterile diluent to obtain 30-300 CFU per plate.

2. Aseptically inoculate agar surface with 0.1ml of a well mixed diluted sample.

3. Using a sterile spreader device, distribute the inoculum evenly over the agar surface.

4. Incubate plates aerobically for 48 +/- 2.0 hours at 35ºC.


Following incubation, examine the plates for growth. Count the number of colonies and express in number of colony forming units (CFU) per gram or milliliter of sample; take into account the dilution factor. If duplicate plates were set-up, express the average for the two plates in terms of the number of microorganisms per gram or milliliter of sample. Consult listed references for additional information on interpretation and enumeration of microbial growth on this medium. (3,4,6-11)



Standard microbiological supplies and equipment such as loops, swabs, pipettes, applicator sticks, spreaders, other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
J 24-48hr 35°C Aerobic Growth
Staphylococcus aureus
ATCC ® 25923
J 24-48hr 35°C Aerobic Growth



1. Bowers and Hucker. 1935. The composition of media for the bacteriological analysis of milk. Tech Bull. N.Y. State Agr. Expt. Sta. No. 228.

2. Bowers and Hucker. 1936. Further studies of the composition of media for the bacteriological analysis of milk. Am. J. of Public Health . Vol. 26.

3. Standard Methods of Milk Analysis , 6th ed. 1934.

4. Standard Methods for the Examination of Dairy Products , APHA, New York, N.Y.

5. Kim and Feng. 2001. In Downes and Ito (ed.) , Compendium of Methods for the Microbiological Examination of Foods , 4th ed. 1992. APHA, Washington, D.C.

6. Standard Methods for the Examination of Water and Waste Water , 21st ed. 2005. APHA, Washington, D.C.

7. Association of Official Agricultural Chemists, 10th ed. p. 737; 1965.

8. Association of Official Analytical Chemists . 1990. Official Methods of Analysis , 15th ed. AOAC, Washington, D.C.

9. The Official Compendia of Standards. 2008. USP27-NF22 . United States Pharmacopeial Convention, Rockville, MD.

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

11. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA. .

12. Am. J. Pub. Hyg. 1910. 6:315-345.

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