The medium comply with the recommendations of USP, EP and APHA. Formulation is identical to Fluid Thioglycollate Medium with the exception that synthetic agar-agar is used.
Mode of Action
This culture medium is more transparent than the classical Thioglycollate Medium and is therefore especially suitable for performing sterility tests when large volumes and long incubation periods are required. The reducing components thioglycollate and cystine ensure adequate anaerobiosis even in the case of fastidious anaerobes. Possible entry of atmospheric oxygen is indicated by the redox indicator resazurin, which then changes its colour to red. Addition of calcium or magnesium ions to the culture medium increases its solidity.
Typical Composition (g/litre)
Peptone from casein 15.0; yeast extract 5.0; D(+)glucose 5.5; L-cystine 0.5; sodium chloride 2.5; sodium thioglycollate 0.5; sodium resazurin 0.001; gelling agent (synthetic agar-agar) 0.75.
Suspend 29 g/litre, dispense into tubes or flasks and autoclave (15 min at 121 °C)
pH: 7.1 ± 0.2 at 25 °C.
The prepared medium is clear and yellow.
The culture medium should, if possible, be freshly prepared. After autoclaving, it should not be placed
immediately in the refrigerator, but should be allowed to cool at room temperature to minimize entry of atmospheric oxygen. The prepared medium can be stored for up to 3 months in an air-tight vessel. It is not for use, if more than one third has turned pink due to the entry of oxygen and if this colouration does not disappear on heating once
Experimental Procedure and Evaluation
Inoculate the culture medium with the sample to the bottom of the vessel. In order to ensure anaerobiosis, the medium can then be covered with an approximately 1 cm layer of sterile liquid
Incubation: several days at 30 – 35°C aerobically or as otherwise specified. Anaerobes grow in the lower part of the culture tube.
The classical thioglycollate culture medium should be used to test materials that contain large amounts of calcium or magnesium ions