HiMedia Laboratories GmbH, Marie-Curie-Str. 3, 64683, Einhausen, Germany.
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Intended Use
Letheen Agar is recommended to determine the phenol coefficient of quaternary ammonium compounds using Escherichia coli or Staphylococcus aureus ATCC 6538.
Composition**
| Ingredients | Gms / Litre |
|---|---|
| Casein enzymic hydrolysate | 5.000 |
| Beef extract | 3.000 |
| Dextrose | 1.000 |
| Polysorbate 80 | 7.000 |
| Lecithin | 1.000 |
| Agar | 15.000 |
Final pH (at 25°C): 7.0±0.2
**Formula adjusted, standardized to suit performance parameters
Directions
Suspend 32 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well and dispense as desired.
Principle And Interpretation
Letheen Agar is a modification of Tryptone Glucose Extract Agar with the supplementation of lecithin and Polysorbate 80. This medium is used to neutralize the quaternary ammonium compounds in the testing of germicidal activity. The addition of lecithin and Polysorbate 80 was suggested by Weber and Black (1).
Letheen Medium is also recommended for testing of cosmetics 4). Beef extract, casein enzymic hydrolysate and dextrose supply essential nutrients and other trace elements for the microbial growth. Lecithin and polysorbate 80 enables the recovery of bacteria from solutions containing residues of disinfectant used in sanitization of utensils and equipments. Lecithin neutralizes quaternary ammonium compounds and polysorbate 80 neutralizes phenolic disinfectants, hexachlorophene and formalin (2,3). Dehydrated medium may appear moist with brown sugar appearance, which does not indicate deterioration (3).
Quality Control
Appearance
Cream to yellow homogeneous free flowing powder
Gelling
Firm, comparable with 1.5% Agar gel
Colour and Clarity of prepared medium
Light yellow coloured clear to slightly opalescent gel forms in Petri plates
Reaction
Reaction of 3.2% w/v aqueous solution at 25°C. pH: 7.0±0.2
pH
6.80-7.20
Cultural Response
M414: Cultural characteristics observed after an incubation at 35-37°C for 24-48 hours.
| Organism | Inoculum (CFU) | Growth | Recovery |
|---|---|---|---|
| Escherichia coli ATCC 25922 | 50-100 | good - luxuriant | >=70% |
| Staphylococcus aureus ATCC 6538 | 50-100 | good - luxuriant | >=70% |
Storage and Shelf Life
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
Reference
- Weber and Black, 1948, Soap Sanitary Chem., 24:134.
- Favero (Chm.), 1967, A State of the Art Report, Biological Contamination Control Committee, American Association for Contamination Control.
- MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore
- American Society for Testing and Materials, 1991, Standard Test Methods for preservatives in water-containing cosmetics, E640-78. Annual Book of ASTM Standards, ASTM, Philadelphia, Pa.
| Product Name | Letheen Agar |
|---|---|
| SKU | M414 |
| Product Type | Regular |
| Physical Form | Powder |
| Origin | Animal |
| Packaging type | HDPE |
| References | 1. Carpenter and Morton, 1947, Proc. N.Y. State Assoc. Public Hlth. Labs., 27:58. 2.Carpenter et al, 1949, Am. J. Syphil. Gonorrh. Vener. Dis., 33:164. 3.Martin, Billings, Hackney and Thayer, 1967, Public Hlth. Rep., 82:361. 4.Thayer J. and Martin J.E. Jr., 1966, Public Health Rep., 81:559. 5.Martin J.E. Jr. and Lester A., 1971, HSMHA Hlth. Service Rep., 86(1):30. 6.MacFaddin J., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. I, Williams andWilkins, Baltimore. |
| Customized Product Available | No |
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