This medium is intended primarily for use in sterility testing of biological fluids that are turbid or viscous and is recommended in the United States Pharmacopoeia. It can be used for the cultivation of both aerobic and anaerobic organisms.
The yeast extract, tryptone and glucose act as carbon, nitrogen and vitamin sources in this medium. The inclusion of sodium thioglycollate and L-cystine ensure anaerobiosis even for many of the more fastidious anaerobes and they also inactivate mercury and many other heavy metallic compounds. Resazurin is an oxidation-reduction indicator which turns pink when oxidised and is colourless when reduced. Sodium chloride maintains osmotic balance. Agar reduces oxygen diffusion into the medium.
NB – For best results it is recommended that the medium be heated in a boiling water bath, with the cap loosened, and then allowed to cool, with the cap tightened, immediately before use. The cap must be replaced on the container immediately after inoculation.