Purpose: Liquid thioglycolic medium is recommended for tests on the sterility of biological products and for the selection of many aerobic and anaerobic organisms. Brief description and explanation: Quastel and Stephenson noticed that the presence of a small number of compounds containing SH-groups (cysteine, thioglycolic acid, glutathione) provides "aerobic" growth of Clostridium sporogenes in a tryptocyte broth. Falk, Bucca and Simmons found the benefits of using small amounts of agar (0.06-0.25%) when detecting contaminants during tests on the sterility of biological agents. Brewer demonstrated the importance of combining a small amount of agar and reducing agents. Brever's experiments have shown that anaerobes grow equally well in a liquid medium containing 0.05% agar, regardless of the presence or absence of thioglycolate sodium. Marshall, Gunnish, and Luxen reported satisfactory growth of anaerobes on a brewer's thioglyctic medium in the presence of a mercury preservative. The neutralization of the bacteriostatic action of mercury compounds with sodium thioglycol has been confirmed by Nungester, Hood and Warren and Portwood. Vera has included casein pepton. Malin and Finn reported that a widely used environment containing thioglycolate suppresses some organisms in the presence of hydrocarbons. The liquid thioglycolic medium is recommended by the FDA in the Bacteriological Analytical Guide and in the Official Methods of the AOAC for food testing and for determining the phenolic factor and sporicidal effect of disinfectants. Liquid thioglycolic medium is also used to check the sterility of canned blood. This is one of the environments recommended in the USP for use in sterility tests for potentially sterile products.

Principle of action: Liquid thioglycolic medium contains high-yielding hydrolyzate of casein, yeast extract and lycistine, which support the lush growth of demanding microorganisms. Glucose is a fermentable carbohydrate, and a source of energy. Thioglycolate sodium and L-cystines allow clostridium growth even in aerobic conditions. A small amount of agar contributes to the growth of aerobes, as well as anaerobes in the environment, even if thioglycollate sodium is removed from the environment, and also helps in maintaining a low oocyte-based potential to stabilize the environment. Sodium thioglycollate acts as a reducing agent and neutralizes the toxic effects of mercury preservatives and peroxides that are formed in the environment, thus contributing to anaerobiosis, and makes the environment suitable for testing materials containing heavy metals. Resazurin is an indicator dye; with a slight increase in the oxygen content of resazarin changes color to red.

Storage:

Pancreatic hydrolyzate casein - 15,00 grams / liter

Yeast extract - 5,00 grams / liter

Glucose - 5.50 grams / liter

Sodium chloride - 2.50 grams / liter

L-cystine - 0.50 grams / liter

Thioglycolate sodium - 0,50 grams / liter

Resazirin chloride - 0.001 grams / liter

Agar - 0.75 grams / liter

Preparation:

1. Mix 29.75 g of dry medium in 1000 ml of distilled water.

2. Heat, if necessary, until complete dissolution of the particles.

3. Sterilize with autoclaving at 1.1 bar (121 ° C) for 15 minutes.

4. Cool to 25 ° C and store in a dark, cool place, preferably at a temperature below 25 ° C.

Test procedure: For more information on standard test procedures, see the relevant links.

Results:

1. After incubation, the presence of growth is evidenced by the appearance of turbidity in comparison with the untreated control.

2. Strict aerobic tends to grow in a thin layer on the surface of the broth; obligate anaerobes will grow only in the part of the broth located below the upper oxidized layer.

Limit procedure:

1. Anaerobes may overlap with more rapid growth of optional organisms.

2. If the cups with the medium do not show any growth, study the broth by Gram stain.

3. Never rely solely on broth cultures to select anaerobes. Some anaerobes can be inhibited by metabolic products or acids produced by optional anaerobes that grow more rapidly.

4. For detailed information and guidance on procedures, refer to the relevant texts.

Delivery time: 5 d.

Information updated: 02.03.2018