Brewer (1) formulated Fluid Thioglycollate Medium for rapid cultivation of aerobes as well as anaerobes by adding a reducing agent and small amount of agar. The USP (2), BP (3), EP (4)and AOAC (5) have recommended the media for sterility testing of antibiotics, biologicals and food products and for determining the phenol coefficient and sporicidal effect of disinfectants. However, it is intended for the examination of clear liquid or water-soluble materials. Dextrose monohydrate, pancreatic digest of casein, yeast extract, L-cystine provide the growth factors necessary for bacterial multiplication. Sodium thioglycollate and L-cystine act as a reducing agent lowering the oxidation-reduction potential by removal of oxygen This condition helps to prevent the accumulation of peroxides which is toxic in nature. The SH group also neutralizes the antibacterial effect of mercurial preservatives and other heavy metal compounds which exert a bacteriostatic effect in the materials under examination. Any increase in the oxygen content is indicated by a color change of redox indicator resazurin; to red (6,7,8). The small amount of agar helps in maintaining low redox potential and stabilizes the medium (9). In sterility checking, it is recommended to dilute the sample containing preservatives, with this broth to reduce the toxicity and enhance the growth of contaminants, if any.
Application: For Sterility Testing of Biologicals and for Cultivation of Aerobes, Anaerobes and Microaerophiles in Accordance with US Pharmacopoeia