For sterility testing of biologicals and for cultivation of aerobic, anaerobic and microaerophilic organisms. FLUID THIOGLYCOLLATE MEDIUM is usedfor sterility testing of biological and for cultivation of anaerobic, and microaerophilic organisms.“Brewer” formulated this mediumand is recommended by USP.The mediais also usedfor sterility testing of antibiotics, biologicaland foods andalso for determining the phenol coefficient and sporicidal effect of disinfectants. However, it is intended for the examination of clear liquid or water-soluble materials. Fluid Thioglycollate Medium is also routinely used to check the sterility of stored blood in blood banks.The mediumcontains Pancreaticdigest of casein andYeast extract thoseprovidesthe nitrogen and essential growth enhancersnecessary for bacterial multiplication. Sodium thioglycollate and L-Cystineactsas a reducing agent which maintains a low oxygen tension by removing molecular oxygen from the environment.Indicator Resazurin dispensed throughout the media causing the media to appear pink in colourin oxidizedstate.Dextrose is a fermentable energy source. Addition of small amount of agar helps in maintaining low redox potential for stabilizing the medium. Addition of agar in small amount favors the growth of aerobes as well as anaerobeswhich retards dispersion of CO2, diffusion of oxygen, and reducing substances.On incubation at30 -350C for 48-72 hours shown luxuriant growth in all the culture strains tested.Sodium chloride helps maintaining the osmotic balance.
Dextrose, Tryptone and yeast extract, provide the growth factors necessary for bacterial multiplication. Sodium thioglycollate and L-cystine act as a reducing agent and neutralizes the toxic effects of mercurial preservatives and peroxides formed in the medium, thereby promoting anaerobiosis, and making the medium suitable to test materials containing heavy metals. The small amount of agar used in the medium favors the growth of aerobes as well as anaerobes in the medium and also helps in maintaining low redox potential for stabilizing the medium. Any increase in the oxygen content is indicated by a colour change of redox indicator, resazurin to red.