CRITERION™ DEXTROSE TRYPTONE AGAR

Cat. no. C5620 CRITERION™ Dextrose Tryptone Agar 60gm
Cat. no. C5621 CRITERION™ Dextrose Tryptone Agar 500gm
Cat. no. C5622 CRITERION™ Dextrose Tryptone Agar 2kg
Cat. no. C5623 CRITERION™ Dextrose Tryptone Agar 10kg
Cat. no. C5624 CRITERION™ Dextrose Tryptone Agar 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Dextrose Tryptone Agar is used for cultivating thermophilic "flat-sour" microorganisms associated with food spoilage.

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

Dextrose Tryptone Agar is used for isolating "flat-sour" organisms from food products. "Flat-sour" spoilage of canned foods is caused by Bacillus coagulans ( Bacillus thermoacidurans). Bacterial growth results in a 0.3-0.5 drop in pH, while the ends of the can remain flat.

B. coagulans is a soil microorganism that can be found in canned tomato products and dairy products. Conditions favorable for multiplication of the bacterium can result in spoilage of the food product.(2)

Dextrose Tryptone Agar can also be used to isolate other food spoilage bacteria: mesophilic aerobic spore-formers in the genera Bacillus and Sporolactobacillus and thermophilic "flat-sour" spore-formers such as B. stearothermophilus.(2)

FORMULA

Gram weight per liter: 30.0gm/L
Tryptone 10.0gm
Dextrose 5.0gm
Bromcresol Purple 0.04gm
Agar 15.0gm

Final pH 6.7 +/- 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 greenish-beige.

Store the prepared media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 30.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

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

4. Cool to 45-50ºC. Aseptically dispense into sterile petri dishes.

PROCEDURE AND INTERPRETATION OF RESULTS

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

LIMITATIONS

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
Bacillus stearothermophilus
ATCC ® 12980
A 36-48hr 55°C Aerobic Growth; color change from purple to yellow

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Dextrose Tryptone Agar powder should appear homogeneous, free-flowing and light greenish-beige in color. The prepared media should appear slightly opalescent, without significant precipitate, and purple in color.

REFERENCES

1. National Canners Association. Bacterial standards for sugar. 1933.

2. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. American Public Health Association, Washington, D.C.


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

052316gr