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Letheen Broth Base, AOAC (Powder)


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Letheen Broth Base is used with Polysorbate 80 for the testing of quaternary ammonium compounds for antimicrobial acitivity. Polysorbate 80 is not supplied.
In 1948, Weber and Black described the value of a highly nutitional solid medium containing neutralizing agents for quaternary ammonium compounds for sanitizers (1). The addition of Lecithin and Polysorbate 80 to Tryptone Gluse Extract (TGE) Agar resulted in a medium that effectively neutralizes quaternary ammonium compounds while testing germicidal activity. Letheen Agar is a modification of TGE Agar with the addition of Lecithin and Polysorbate 80.
Catalog #L1672-10
Letheen Base was developed as a subculture medium for the neutralization of quaternary ammonium compounds in disinfectant testing. Quisno, Gibby and Foter discovered that adding lecithin and Polysorbate 80 to FDA Broth results in a medium that neutralized high concentrations of quaternary ammonium salts (2). he resulting medium, termed Letheen (a combination of Lecithin and Tween) was easy to prepare and clear in appearance, aiding to visual inspection for growth. Letheen Broth Base is recommended by the Association of Official Analytical Chemists (AOAC) for use with disinfectants containing cationic surface materials.
Letheen Broth Base is specified for use by the American Society for Testing Materials (ASTM) in Standard Test Method for Presernatives in Water-Containg Cosmetivcs (4). Total neutralization of disinfectants is critical. Disinfectant residues can results in false negative (no growth) tests.
Principles of the Procedure
Enzymatic digest of Animal Tissue and Beef Extract provide nitrogen, carbon, vitamins, and minerals in Letheen Broth Base. Sodium Chloride maintains the osmotic balance. Lecithin neutralizes quaternary ammonium compouNone Detectedsand Polysorbate 80 neutralizes phenols, hexachloraphene, formalin, and with Lecithin, ethanol (2,5-7).
PowderPowder is homogeneous, free flowing and beige
SolutionPrepared medium is gold to amber, and clear to slight hazy with no to slight precipitate.
Expected Cultural ResponseLetheen Borth Base at 35C after 18-24 hours incubation:
Enterococcus faecalis ATCC 29212Growth
Escheria coli ATCC 25922Growth
Pseudomonase aeruginosa ATCC 27853Growth
Staphylococcus aureus ATCC 25923Growth
Staphylococcus epidermidis ATCC 12228Growth
1. Dissolve 20.7g of the medium and 5g Polysorbate 80 in 1L distilled water.
2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
3. Autoclave ate 121C for 15 minutes.
Test Procedures and ResultsConsult appropriate references for complete information (3,4).
StorageStore sealed bottle containing dehydrated medium at 2-30C. Once opened and recapped, place container in a low humidity environment at the same storage temperature. Protect from moisture and light, keeping container tightly closed. The dehydrated medium should be discarded if not free flowing or the color has changed from the original color.
Due to nutritional variations, some strains may be encountered that grow poorly or fail to grow on this medium.
Important NoteThis product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological.

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