Alternative Thioglycollate Medium is formulated as described in the N.I.H. memorandum (1). It is used for the sterility testing of certain biological products which are turbid or viscous and cant be tested using Fluid Thioglycollate Medium (M009). Both the media have similar composition, except agar and resazurin that are not included in Alternative Thioglycollate Medium. This deletion makes it suitable for sterility testing of viscous products.
Casein enzymic hydrolysate and yeast extract serve as source of essential nutrients to the contaminants, if present. Dextrose serves as the energy source. Sodium chloride maintains the osmotic equilibrium of the medium whereas L-cystine, an amino acid, also serves as source of essential growth factors. Sodium thioglycollate and L-cystine lower the oxidation-reduction potential of the medium by removing oxygen to maintain a low Eh. Sodium thioglycollate also helps to neutralize the toxic effects of mercurial preservatives (2, 3).
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
1. N.I.H. Memorandum, 1955: Culture Media for Sterility Tests, 4th Revision.
2. Nungester, Hood and Warren, 1943, Proc. Soc. Exp. Biol. Med., 52: 287
3. Portwood, 1944, J. Bacteriol., 48: 255