CRITERION™ LETHEEN AGAR

Cat. no. C7360 CRITERION™ Letheen Agar 56gm
Cat. no. C7361 CRITERION™ Letheen Agar 500gm
Cat. no. C7362 CRITERION™ Letheen Agar 2kg
Cat. no. C7363 CRITERION™ Letheen Agar 10kg
Cat. no. C7364 CRITERION™ Letheen Agar 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ 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. Letheen Agar is used as a quaternary ammonium compound neutralizer for the sampling of environmental surfaces.

Letheen media is formulated according to the guidelines set by the AOAC for the determination of phenol coefficient of quaternary ammonium compounds.(1) The medium contains beef extract and pancreatic digest of casein to provide a nutrient rich medium supporting the growth of a variety of microorganisms. Germicidal or disinfectant residue is neutralized by the addition of lecithin and Tween® 80 (Polysorbate 80). Neutralization of these residues reduces their inhibitory effect which would ultimately result in the lowering of the microbial count. Quaternary ammonia compounds are neutralized by lecithin while phenolic disinfectants and hexachlorophene are neutralized by Tween® 80. Together, lecithin and Tween® 80 neutralize ethanol.

FORMULA

Gram weight per liter: 32.0gm/L
Tween® 80 7.0gm
Pancreatic Digest of Casein 5.0gm
Beef Extract 3.0gm
Dextrose 1.0gm
Lecithin 1.0gm
Agar 15.0gm

Final pH 7.0 +/- 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 2-8ºC. 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 homogeneous, moist, and lumpy 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 28.0gm 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.

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. G42.

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
Escherichia coli
ATCC® 25922
A 24-48hr 35°C Aerobic Growth
Staphylococcus aureus
ATCC® 25923
A 24-48hr 35°C Aerobic Growth
Salmonella enterica
ATCC® 14028
A 24-48hr 35°C Aerobic Growth

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Letheen Agar powder should appear homogeneous, moist, and lumpy, and light beige in color. The prepared media should appear clear, with a slight opalescence, and light amber in color.

REFERENCES

1. Helrich, Kenneth, ed. 1990. Official Methods of Analysis, 15th ed. AOAC, Arlington, Virginia.


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

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