Ready-to-use media
Letheen Broth Modified ISO
Liquid medium for the primary recovery of stressed microorganisms in the microbial examination of cosmetics according to FDA and ISO normative.
- Cat. No.
- LC-5163
- Category
- Ready-to-use media
- Format
- 10 x 90 mL flasks
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 4 months
- Also available
- Ready-to-use medium, 1 format (LC-4031)
In the early 40's, Weber and Black recommended the use of lecithin and polysorbates to neutralize the antimicrobial action of the Quaternary Ammonium Compounds (QAC's).
Key features
Applications
Enrichment with neutralizers (general use).
Industry
Cosmetics.
Presentation
10 prepared bottles, 125 mL, with 90 ± 3 mL.
Packaging
1 box with 10 bottles 125 mL. Injectable cap: plastic screw inner cap. The use of syringe needles with a diameter greater than 0.8 mm is not recommended.
Description and technique
Description
In 1965 the methodology was accepted by the AOAC for antimicrobial assays and extends their use to all the cationic surfactants (detergents). The TAT (Tryptone-Azolectin-Polysorbate) medium, in the Newburger Cosmetic Analysis Manual (2nd ed., 1977), is similar in composition and uses the AOAC formulation. In 1978 the FDA (Bacteriological Analytical Manual, 5th edition, 1978) incorporated it as a primary presumptive and enrichment medium for all microbial examination of cosmetics.
The present formulation appears in the 8th edition (1998) of the BAM and the notable modifications are the inclusion of sodium chloride providing suitable osmotic pressure and an increased amount of peptones and tissue extracts to promote good growth; these transform this medium into a very rich all-purpose medium suitable for neutralizing almost all preservatives present in samples under examination.
The ISO Technical Committee on Cosmetics (ISO/TC 217) (2006) has also adopted the present formulation as an alternative enrichment medium prior to microbiological examination, but ideally Eugon LT100 Broth should be employed for this.
Technique
Collect, dilute and prepare samples and volumes as required according to specifications, directives, official standard regulations and/or expected results. Dispense liquid medium in appropriate containers if the original container is of large volume.
Inoculate aseptically the bottles/tubes with the prepared sample or its dilution.
Incubate the tubes tightly closed aerobically at 30-35 °C for 24-48-72 h.
(Incubation times, temperature and sample volumes may vary depending on the sample, on the specifications, etc.)
Read the turbidity increase as growth indicator.
This medium can be used to inoculate any confirmatory, secondary medium by streaking methodology or by spiral method; after proper incubation, enumerate all the colonies that have appeared onto the surface of the secondary agar.
Each laboratory must evaluate the results according to their specifications.
Calculate total microbial count per mL of sample by multiplying the average number of colonies per plate by the inverse dilution factor if a diluted sample was streaked. Report results as colony forming units (CFU) per mL or g along with enrichment and secondary media used, incubation time and temperature.
Presentation
| Presentation | 10 prepared bottles, 125 mL |
|---|---|
| Filling | 90 ± 3 mL |
| Packaging | 1 box with 10 bottles 125 mL. Injectable cap: plastic screw inner cap. The use of syringe needles with a diameter greater than 0.8 mm is not recommended. |
Composition
| Ingredient | g/L |
|---|---|
| Casein peptone | 5.00 |
| Meat peptone | 20.0 |
| Meat extract | 5.00 |
| Yeast extract | 2.00 |
| Lecithin | 0.70 |
| Sodium chloride | 5.00 |
| Polysorbate 80 | 5.00 |
| Sodium bisulfite | 0.10 |
Quality control
Physical/chemical control
| Color | Yellowish-brown |
|---|---|
| pH | 7.0 ± 0.2 at 25 °C |
Microbiological control
Prepare tubes - inoculate with 100 ± 20 CFU for growth promotion or 10⁴-10⁶ CFU (selectivity).
Analytical methodology according to ISO 11133:2014/Amd 1:2018; A2:2020.
Aerobiosis. Incubation at 30-35 °C. Reading at 24-48 h, until 72 h.
| Microorganism | Growth |
|---|---|
| Ps. aeruginosaATCC 9027, WDCM 00026 | Good |
| Staphylococcus aureusATCC 6538, WDCM 00032 | Good |
| Bacillus subtilisATCC 6633, WDCM 00003 | Good |
| Escherichia coliATCC 25922, WDCM 00013 | Good |
| Salmonella typhimuriumATCC 14028, WDCM 00031 | Good |
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- ASTM Standard E 640-78 (1991) Test Method for the preservatives in water-containing cosmetics. Philadelphia. PA. USA.
- ATLAS, R.M., L.C. PARKS (1993) Handbook of Microbiological Media. CRC Press, Inc. London.
- FDA (Food and Drug Administration) (1998) Bacteriological Analytical Manual 8th ed. Rev. A. AOAC International. Gaithersburg. MD. USA.
- HORWITZ, W. (2000) Official Methods of Analysis. AOAC International. Gaithersburg. MD. USA.
- ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
- ISO 21149 Standard (2017) Cosmetics - Microbiology - Enumeration and detection of aerobic mesophilic bacteria.
- ISO 21150 Standard (2015) Cosmetics - Microbiology - Detection of Escherichia coli.
- ISO 22717 Standard (2015) Cosmetics - Microbiology - Detection of Pseudomonas aeruginosa.
- ISO 22718 Standard (2015) Cosmetics - Microbiology - Detection of Staphylococcus aureus.
- LUCAS, I.P. (1977) Microbiological Examination of Cosmetics. Newburger's Manual of Cosmetic Analysis AOAC. Washington.
- US PHARMACOPOEIA (2002) <61> Microbial Limit Tests. 25th ed. US Pharmacopeial Convention. Rockville. MD. USA.
- WEBER, G.R. & L.A. BLACK (1948) Relative efficiency of quaternary inhibitors. Soap and Sanit. Chem. 24:134-139.
What you receive
The product
Shipped under controlled temperature when the product requires it.
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