Thioglycollate Broth or Fluid Thioglycollate medium is used for sterility testing of antibiotics, biologicals specimen such as stored blood in blood banks,foods and for determination of the phenol coefficient and sporicidal effect of disinfectants.It is also used for the culture and isolation of obligate,facultative anaerobic and microaerophilic bacteria.
Principle of Thioglycollate Broth
- It contains dextrose, tryptone, yeast extract, L-cystine which provide the growth factors necessary for bacterial multiplication.
- L-cystine and sodium thioglycollate allows Clostridium species to grow in the medium even under aerobic conditions.
- The small quantity of agar used in the medium favors the growth of aerobes as well as anaerobes in the medium, even if sodium thioglycollate is removed from the medium.
- Sodium thioglycollate 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.
- Any increase in the oxygen content is indicated by a colour change of redox indicator, resazurin to red
- The small amount of agar also helps in maintaining low redox potential for stabilizing the medium
thioglycollate broth composition
|Ingredients||Grams / Litre|
|Final pH at temperature 25°C||7.1±0.2|
How to Prepare Thioglycollate Broth(How do you make thioglycollate broth?)
- In order to prepare this growth medium,start by suspending 29.75 grams in 1000 ml distilled water.
- Heat to boiling in order to dissolve the medium completely then dispense into tubes.
- Sterilize medium by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
- Cool to a temperature of 25°C and store in a cool dark place preferably below 25°C.
Also note that If in case more than the upper one-third of the medium has acquired a pink colour, the medium may be restored once by heating in a water bath or in free flowing steam until the pink colour disappears.
Appearance of Medium after preparation
It appears light straw coloured (yellowish), clear to slightly opalescent solution with upper 10% or less medium pink on standing.
Type of Inoculums
- Pharmaceutical samples for sterility testing
- Wound exudates
- Skin swab
- Vaginal,anal or urethral swab etc
thioglycollate broth procedure
- 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 for several days at the optimal incubation temperature of 35-37 °C
- Anaerobes grow in the lower part of the culture.
Cultural Response on Thioglycollate Broth
These Cultural characteristics are observed after an incubation at 30-35°C for not more than 3 days
|Clostridium sporogenes||luxuriant (anaerobic)|
|Bacteroides vulgatus||good (anaerobic)|
|Escherichia coli||luxuriant ( Facultative Anaerobe)|
|Clostridium perfringens||luxuriant (anaerobic)|
|Streptococcus pneumoniae||luxuriant( Facultative anaerobic)|
Limitations with Thioglycollate Broth
This medium is intended for the examination of clear liquid or water-soluble materials.
- Brewer, 1940, J. Am. Med. Assoc., 115:598.
- The United States Pharmacopoeia, 2018, The United States Pharmacopoeial Convention, Rockville, MD.
- British Pharmacopoeia, 2016, The Stationery office British Pharmacopoeia
- European Pharmacopoeia, 2017, European Dept. for the quality of Medicines.
- Williams H., (Ed.), 2005, Official Methods of Analysis of the Association of Official Analytical Chemists, 19th Ed., AOAC, Washington, D.C
- Marshall, Gunnison and Luxen, 1940, Proc. Soc. Exp. Biol. Med., 43:672.
- Nungester, Hood and Warren, 1943, Proc. Soc. Exp. Biol. Med., 52:287. 8.Portwood,