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Tryptic Soy Agar (TSA): Composition, Preparation and Uses

Tryptic Soy Agar is a universal medium which supports the growth of wide variety of microorganisms (both gram positive as well as gram negative bacteria grow in this medium). 

It is used for the isolation and cultivation of wide variety of microorganisms.

Tryptic Soy Agar (TSA) is mainly used as an initial growth medium for the purposes of observing colony morphology, developing a pure culture and achieving sufficient growth for further biochemical testing and culture storage. TSA slants are being used to store and ship bacterial cultures.

Composition of Tryptic Soy Agar (TSA)

Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 15.0gm
Peptic Digest of Soybean Meal 5.0gm
Sodium Chloride 5.0gm
Agar 15.0gm

Final pH 7.3 +/- 0.2 at 25°C

Tryptic Soy Agar contains digests of casein and soybean meal.  The combination of casein and soy peptones renders the medium nutritious by supplying organic nitrogen, particularly amino acids and longer-chained peptides. Sodium chloride is added to maintain the osmotic equilibrium and agar is the solidifying agent.


TSB Medium Preparation

  1. Weight 3 gm of Tryptic soy broth (TSB) powder and dissolve in 100 ml distilled water.
  2. Place the bottle on magnetic stirrer to mix.
  3. Aliquot 10 ml of the medium to each 13*100 mm glass spiral tubes (or other suitable container as per your need).
  4. After aliquot, place all tubes into autoclave at 121°C for 15 minutes.
  5. Remove the tubes and make sure the cap of tube is closed tightly.
  6. Fully cool autoclaved tubes at room temperature before placing stock in 4°C refrigerator and avoid light. Pre-warm the medium to room temperature before usage.
Tryptic Soy Agar Plate (source:mkldiagnostics)

Usage of Tryptic Soy Agar (TSA)

Tryptic Soy Agar (TSA) is recommended for use as a general growth medium for the isolation and cultivation of microorganisms. Tryptic Soy Agar supports the growth of nonfastidious as well as moderately fastidious microorganisms. This medium is recommended for use in the cultivation, storage, maintenance and transportation of pure cultures of microorganisms.

Use of TSA in clinical microbiology is limited as it does not support the growth of variety of fastidious bacteria. TSA is not used for the isolation of pathogens from clinical specimens but may be used for maintaining or subculturing bacterial strains (e.g. , Enterobacteriaceae and  Staphylococci). After supplementation with blood (e.g. 5% sheep blood), TSA may be used as a primary isolation medium in clinical microbiology. Tryptic Soy Agar can be used in determining the X, V and XV factors requirements of Haemophilus species by using strips or discs containing X, V and XV factors in the inoculated plates.

Tryptic Soy Agar containing various salt concentrations are also available which are recommended for use in determining the halotolerance levels of microorganisms.