Fluid Thioglycollate Medium

Fluid Thioglycollate Medium (FTM)

EMD Cat. No. 1.08191.0500/5000

500 g, 5 kg

For cultivation and isolation of obligate and facultative anaerobic and microaerophilic bacteria and for sterility tests.

Both culture media comply with the recommendations of United States Pharmacopeia XXIII (1995), the European Pharmacopeia and APHA (1992).


Experimental Procedure and Evaluation	Preparation
Typical Composition (g/liter)	Literature

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 and helps maintain the stratification of organisms growing in different layers of the broth. Oxygen is driven out of the broth by autoclaving, but as the broths sit at room temperature, oxygen begins to diffuse back into the tube. Any increase in the oxygen content is indicated by the redox indicator sodium resazurin which changes its color to red. Obligate aerobes will only grow in this oxygen-rich top layer. Obligate anaerobes will only grow in the lower areas of the tube. Microaerophiles will grow in a thin layer below the richly-oxygenated layer. Facultative or aerotolerant anaerobes can grow throughout the medium but will primarily grow in the middle of the tube, between the oxygen-rich and oxygen-free zones.

Typical Composition (g/liter)
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.

Preparation

Suspend 30 g/liter, dispense into tubes, autoclave
(15 min at 121°C).
pH: 7.1 ± 0.2 at 25°C.
The prepared medium is clear and yellowish.
The culture medium 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 coloration 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 1 cm 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.

Quality control

Test strains	Growth
Staphylococcus aureus ATCC 6538-P	good
Bacillus subtilis ATCC 6633	good
Clostridium sporogenes ATCC 19404	good (anaerobic)
Bacteroides vulgatus ATCC 8482	good (anaerobic)
Candida albicans ATCC 10231	good
Candida albicans ATCC 2091	good
Escherichia coli ATCC 25922	good

Additives

EMD Cat. No.	Product	Pack Size
1.01614.1000	Agar-agar purified	1 kg
PX0046-1	Paraffin viscous	1 l

Literature

American Public Health Association: Compendium of methods for the microbiological examination of foods. - 3rd ed. (1992).
European Pharmacopeia II, Chapter VIII. 3.
United States Pharmacopeia XXIII, Chapter "Sterility Tests", 1995.