Letheen Agar is used for evaluating the bactericidal activity of quaternary ammonium compounds, and is used with Letheen Broth to determine the suitability of preservatives for use in cosmetic formulations, as specified by the American Society for Testing and Materials (ASTM), Standard Test Method for Preservatives in Water- Containing Cosmetics.

Letheen Agar is a modification of Tryptone Glucose Extract (TGE) Agar, and is formulated to neutralise quaternary ammonium compounds used in testing of germicidal activity, the importance of which was first described by Weber and Black in 1948.

The addition of Tween® 80 means Letheen Agar also neutralises phenols, hexachlorophene, formalin and ethanol (in the presence of lecithin). Letheen Agar also allows calculation of colony forming units to be assessed, when used with a hygiene swabbing protocol and will ensure against disinfectant carry-over from the swabbing diluent/medium.

Related Sector(s)

• Cosmetic

Related Organism(s)

• Disinfectant Testing