Plot No. C40, Road No. 21Y, MIDC, Wagle Industrial Estate, Thane(W)-400604, MH, India
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Letheen Agar, Modified (Modified Letheen Agar)
As low as
$229.90
Availability: Out of stock
Availability: In stock
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SKU:
M946
This medium is recommended for screening cosmetic products for microbial contamination.
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Sterility Testing#CC293D
Intended Use
Recommended for screening cosmetic products for microbial contamination.
Composition
| Ingredients | g/L |
|---|---|
| Peptone | 10.000 |
| Tryptone | 10.000 |
| HM Peptone B # | 3.000 |
| Yeast extract | 2.000 |
| Sodium chloride | 5.000 |
| Lecithin | 1.000 |
| Polysorbate 80 | 7.000 |
| Dextrose (Glucose) | 1.000 |
| Sodium bisulphite | 0.100 |
| Agar | 15.000 |
| Final pH (at 25°C) | 7.2±0.2 |
**Formula adjusted, standardized to suit performance parameters
# - Equivalent to Beef extract
Directions
Suspend 54.1 grams in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C. Mix well and pour into sterile Petri plates.
Principle And Interpretation
In the early 40s, Weber and Black recommended the use of lecithin and polysorbates to neutralize the antimicrobial action of the quaternary ammonium compounds (1). In 1965, the methodology was accepted by AOAC for the antimicrobial assays and extended their use to all the cationic detergents. In 1978, the FDA incorporated it as pre-enrichment medium for every microbial examination of cosmetics. Letheen Agar, Modified is used to partially inactivate the preservatives in cosmetics being analyzed for the microbial content (2). This medium was originally recommended by APHA for use in microbial testing of water (3).
There are great chances of altering the chemical composition of cosmetics by the metabolism of organisms thereby spoiling and causing harm to the users (2,4,5). Direct colony counts and enrichment culturing are the methods of choice for isolating microorganisms from cosmetic products. The word Letheen represents a combination of lecithin and polysorbate (tween) 80. Peptone, tryptone, HM peptone B and yeast extract provide nitrogenous nutrients, carbon compounds, long chain amino acids and trace elements to the microorganisms. Incorporation of lecithin and polysorbate 80 to the medium enables the recovery of bacteria from materials containing residues of disinfectant compounds or preservatives used in cosmetics. Polysorbate 80 is added to nullify phenolic compounds, hexachlorophene, formalin and along with lecithin neutralizes ethyl alcohol (6). Lecithin also neutralizes quaternary ammonium compounds present in the cosmetics. Sodium chloride maintains the osmotic balance of the medium.
Type of specimen
Cosmetic products
Specimen Collection and Handling
For cosmetic samples follow appropriate techniques for handling specimens as per established guidelines (7,8).
After use, contaminated materials must be sterilized by autoclaving before discarding.
Warning and Precautions
Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/ face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.
Limitations
- Further biochemical tests must be carried out for further confirmation.
Performance and Evaluation
Performance of the medium is expected when used as per the direction on the label within the recommended temperature.
Quality Control
Appearance
Cream to yellow homogeneous free flowing powder
Gelling
Firm, comparable with 1.5% Agar gel
Colour and Clarity of prepared medium
Yellow coloured, clear to slightly opalescent gel forms in Petri plates
Reaction
Reaction of 5.4% w/v aqueous solution at 25°C. pH: 7.2±0.2
pH
7.00-7.40
Cultural Response
Cultural characteristics observed after an incubation at 35-37°C for 18-48 hours
| Organism | Inoculum (CFU) |
Growth | Recovery |
|---|---|---|---|
| Escherichia coli ATCC 25922 (00013*) | 50-100 | luxuriant | >=70% |
| Staphylococcus aureus subsp. aureus ATCC 25923 (00034*) | 50-100 | luxuriant | >=70% |
| Staphylococcus aureus subsp. aureus ATCC 6538 (00032*) | 50-100 | good-luxuriant | >=70% |
Key: *Corresponding WDCM numbers.
Storage and Shelf Life
Store between 10-30°C in a tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition Seal the container tightly after use. Product performance is best if used within stated expiry period.
Disposal
User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (7,8).
Reference
- Weber and Black, 1948, Soap Sanitary Chem., 24:134-139
- Smart R. and Spooner D. F., 1972, J. Soc. Cosmet. Chem., 23:721.
- APHA, 1960, Standard Methods for the Examination of Water and Wastewater, 11th Ed., American Public Health Association, New York.
- Dunningan A. P., 1968, Drug Cosmet. Ind., 102:43.
- Wilson L. A. and Ahearn D. G., 1977, Am. J. Opthalmol., 84:112.
- Favero (Chm.), 1967, A State of the Art Report, Biological Contamination Control Committee, American Association for Contamination Control.
- Isenberg, H.D. Clinical Microbiology Procedures Handbook. 2nd Edition.
- Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.
| Product Name | Letheen Agar, Modified (Modified Letheen Agar) |
|---|---|
| SKU | M946 |
| Product Type | Regular |
| Physical Form | Powder |
| Origin | Animal |
| Packaging type | HDPE |
| References | 1.Madden J. M. and Dallas W. S., 1984, Bacteriological Analytical Manual, 6th Ed., AOAC, Arlington, Va.2.APHA, 1960, Standard Methods for the Examination of Water and Wastewater, 11th Ed., American Public HealthAssociation, New York.3.Weber and Black, 1948, Soap Sanitary Chem., 24:134-13 |
| Customized Product Available | No |
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