CRITERION™ MODIFIED LETHEEN AGAR

Cat. no. C7900 CRITERION™ Modified Letheen Agar 118.2gm
Cat. no. C7901 CRITERION™ Modified Letheen Agar 500gm
Cat. no. C7902 CRITERION™ Modified Letheen Agar 2kg
Cat. no. C7903 CRITERION™ Modified Letheen Agar 10kg
Cat. no. C7904 CRITERION™ Modified Letheen Agar 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Modified Letheen Agar is used to determine the antimicrobial activity of quaternary ammonium compounds.

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

Quaternary ammonium compounds are molecules which contain a nitrogen atom with four other atoms bonded to it. Most quaternary ammonium compounds are organic compounds and have biological activity. These compounds often work well as disinfectants, offering bactericidal and bacteriostatic effects. Modified Letheen Agar is used as a quaternary ammonium compound neutralizer for the sampling of environmental surfaces. Quaternary ammonia compounds are neutralized by lecithin while phenolic disinfectants and hexacholorphene are neutralized by Tween® 80. Together, lecithin and Tween® 80 neutralize ethanol.

Modified Letheen Agar is formulated as described in the 7th edition of the U.S. FDA Bacteriological Analytical Manual.(1) Modified Letheen Agar is recommended by the FDA for use in the microbiological testing of cosmetics.(2) The medium contains beef extract and peptone to provide a nutrient rich medium supporting the growth of a variety of microorganisms. The tryptone level was increased in the Modified Letheen Agar formula in order to provide for better growth. The yeast extract not only provides vitamins and co-factors required for growth, but also serves as an additional source of nitrogen and carbon. Sodium chloride provides for osmotic balance.

FORMULA

Gram weight per liter: 59.1gm/L
Letheen Agar 32.0gm
Proteose Peptone No. 3 10.0gm
Tryptone 5.0gm
Sodium Chloride 5.0gm
Yeast Extract 2.0gm
Sodium Bisulfite 0.1gm
Agar 5.0gm

Final pH 7.2 +/- 0.2 at 25 degrees C.

* 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 beige.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 59.1gm 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.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G221.

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
Staphylococcus aureus
ATCC ® 6538
A 24hr 35°C Aerobic Growth
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Growth

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Modified Letheen Agar powder should appear homogenous, free-flowing, and light beige in color. The prepared media should appear clear, slightly opalescent, and light to medium amber in color.

REFERENCES

1. Tomlinson, L. (ed.). 1992. FDA Bacteriological Analytical Manual, 7th ed. AOAC International, Arlington, Virginia.

2. Hitchins, A.D., T.T. Tran and J.E. McCarron. In L.A. Tomlinson, L. (ed.). 1992. FDA Bacteriological Analytical Manual, 7th ed. AOAC International, Arlington, Virginia.

3. Marshall, R.T., ed. 1992. Standard Methods for the Examination of Dairy Products, 16th ed. APHA, Washington, D.C.

4. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. APHA, Washington D.C.

5. Greenberg, A.E., et al. (ed.). 1992. Standard Methods for the Examination of Water and Wastewater, 18th ed. APHA, Washington D.C.

6. FDA. 1995. Bacteriological Analytical Manual, 8th ed. FDA.

7. U.S. Pharmacopeia, 22nd rev. 1990. U.S. Pharmacopeial Convention, Rockville, MD.

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

9. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.

ATCC is a registered trademark of the American Type Culture Collection.
Tween® is a registered trademark of ICI Americas, Inc.


061416gr