Dehydrated culture media
Letheen Agar Modified
For the microbiological analysis of cosmetics.
- Cat. No.
- LC-1111
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Also available
- Ready-to-use medium, 1 format (LC-5162)
Letheen Agar Modified is a modification of Letheen Broth Base. It is highly nutritious and recommended for use in the microbiological testing of cosmetics. It can be used to inactivate quaternary ammonium compounds and other preservatives when establishing the number of bacteria present in cosmetics and other materials.
Key features
Applications
Enumeration with neutralizers (general use).
Industry
Cosmetics.
Preparation
59.1 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Beef extract, casein peptone and meat peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is the source of vitamins, particularly of the B-group. Glucose is the fermentable carbohydrate providing carbon and energy. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Lecithin, polysorbate 80 and sodium bisulfite neutralize quaternary ammonium compounds and partially neutralize the preservative system commonly found in cosmetics. Bacteriological agar is the solidifying agent.
The medium is also used for microbiological samples from surfaces that have been treated with disinfectants.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber, slightly opalescent |
| Final pH (25 °C) | 7.2 ± 0.2 |
| Amount per litre | 59.1 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Glucose | 1 |
| Bacteriological agar | 20 |
| Casein peptone | 10 |
| Lecithin | 1 |
| Beef extract | 3 |
| Meat peptone | 10 |
| Polysorbate 80 | 7 |
| Sodium bisulfite | 0.1 |
| Sodium chloride | 5 |
| Yeast extract | 2 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 59.1 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to 50 °C, mix well and dispense into plates.
Instructions for use
- Prepare and dilute samples in Letheen Broth Modified (LC-1244).
- Using the spread plate technique, inoculate in duplicate 0.1 mL of the diluted samples onto Letheen Agar Modified.
- Incubate one plate of Letheen Agar Modified at 30 ± 2 °C for 48 hours and the other one at 35 ± 2 °C under anaerobic conditions for 2-4 days.
- Incubate the diluted samples from step 1 at 35 ± 2 °C for 7 days. Subculture enriched samples onto Letheen Agar Modified only if there is no growth in the first incubation.
Quality control
Microbiological test
Incubation conditions: 35 ± 2 °C / 18-24 h.
| Microorganism | Specification |
|---|---|
| Staphylococcus epidermidisATCC 12228 | Good growth |
| Escherichia coliATCC 25922 | Good growth |
| Staphylococcus aureusATCC 25923 | Good growth |
Bibliography
- FDA Bacteriological Analytical Manual (BAM) 1995. Microbiological Methods for cosmetics, Letheen Agar (modified). Letheen Broth (modified).
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
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Tracked shipment
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Frequently asked questions
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