Both culture media comply with the recommendations of United States Pharmacopeia XXVI (2003), the European Pharmacopeia and APHA (1992).
Mode of Action
The reducing agents thioglycollate and cystine ensure an anaerobiosis which is adequate even for fastidious anaerobes. The sulfhydryl groups of these substances also inactivate arsenic, mercury and other heavy metal compounds.
The thioglycollate media are thus suitable for the examination of materials which contain heavy metals or heavy metal preservatives. The higher viscosity of the Fluid Thioglycollate Medium prevents rapid uptake of oxygen. Any increase in the oxygen content is indicated by the redox indicator sodium resazurin which changes its colour to red.
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; agar-agar 0.75.
Suspend 30 g Fluid Thioglycollate Medium/litre, dispense intotubes, autoclave (15min at 121 °C).
pH: 7.1 ± 0.2 at 25 °C.
The prepared media are clear and yellowish.
The culture media should always be freshly prepared. Fluid Thioglycollate Medium cannot be used if more than the upper third of the butt has turned pink due to the presence of oxygen and if this colouration does not disappear after boiling once.
Experimental Procedure and Evaluation
Inoculate the culture medium with the sample material taking care that the sample reaches the bottom of the tubes. In order to ensure anaerobiosis, the medium can then be overlayed with 1cm of sterile liquid paraffin or agar solution.
Incubation: several days at the optimal incubation temperature (35-37 °C).
Anaerobes grow in the lower part of the culture