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Tryptose Sulfite Cycloserine agar

Tryptose Sulfite Cycloserine agar

The figure shows three TSC agar plates, where no bacteria have been cultivated on plate A. Clostridium perfringens has been cultivated on plates B and C. Plate C contains lecithin, but not plate B. Note the precipitation zone of diglycerides around the colonies on plate C.- Click on the image to enlarge it.

Image: Ingrid Hansson (SLU), Lise-Lotte Fernström (SLU) & Karl-Erik Johansson (SLU).



Tryptose Sulfite Cycloserine agar (TSC agar) is used for isolation and enumeration of both vegetative cells and spores of Clostridium perfringens in food and clinical samples.

The medium contains:

  • meat peptone (contains amino acids and peptides)
  • soya peptone (contains amino acids and peptides)
  • yeast extract
  • ammonium ferric citrate (see below)
  • sodium disulfite [is reduced to sodium sulfide (by some bacteria), which forms a black precipitate (FeS) with ammonium ferric citrate]
  • lecithin (optional)
  • cycloserin (inhibits the background flora of bacteria)
  • agar (gelifying agent)
  • water

The final pH of the medium should be 7.6.


Hydrogen sulfide (H2S) positve bacteria (as e.g. C. perfringens) form black colonies on TSC agar. If the TSC agar contains lecithin, a precipitation zone will be formed around colonies, which produce lecithinase.

Updated: 2017-05-10.

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Swedish University of Agricultural Sciences