A medium recommended by the Harmonised European Pharmacopoeia for sterility testing. Conforms to USP/EP/JP performance specification.

Casein and yeast extract provide a source of nitrogen, essential vitamins and amino acids. The glucose provides a carbon source and sodium chloride maintains osmotic balance. L-Cystine and sodium thioglycollate act as reducing agents to create an anaerobic environment and maintain a low Eh. This is aided by the low level of agar which reduces the oxygen permeability through the medium. Resazurin is an oxidation indicator which turns from colourless to red/pink when oxidised. Sodium thioglycollate also serves to inactivate mercurial compounds. If after sterilisation more than the upper one third of the medium has become red/pink it may be restored once by heating in a water bath or in free-flowing steam until the colour disappears. Ensure the media is cooled quickly and prevent the introduction of non-sterile air into the containers.