Tryptic Soy Agar can be used to grow microorganisms. These media are non-selective and general-purpose. They provide enough nutrients to support a variety of microorganisms. This medium can also be used to grow, store, maintain, and transport pure microorganism cultures.
Principle of Tryptic Soy Agar (TSA)
Casein digested by the pancreatic enzyme and soybean meal digested by the papaic enzyme supply nitrogen, vitamins, and minerals. This makes it excellent for the growth of numerous types of bacteria, both finicky and not. Glucose is a source of carbohydrates. Phosphate is a media buffer. Sodium chloride preserves the osmotic equilibrium. The solidifying agent is agar.
The medium may be supplemented with blood to aid the development of more finicky bacteria or antimicrobial compounds to allow for the selection of different microbial groups from pure microbiota. Like with any medium, slight adjustments may be made to accommodate certain circumstances.
Composition of Tryptic Soy Agar (TSA)
| Ingredients | Gms/liter |
| Pancreatic digest of casein | 17.000 |
| Papaic digest of soybean meal | 3.000 |
| Sodium chloride | 5.000 |
| Dextrose (Glucose) | 2.500 |
| Dipotassium hydrogen phosphate | 2.500 |
| Agar | 15.000 |
Final pH (at 25°C): 7.3±0.2
Preparation and Method of Use of Tryptic Soy Agar (TSA)
- Take 45 grams and mix it with 1000 ml of distilled water.
- To dissolve the medium completely, heat to boiling
- For 15 minutes, sterilize by using an autoclave at 15lbs pressure (121degC).
- Keep it at 45-50 degrees Celsius
- Mix everything together and pour onto sterilized Petri dishes.
- Before inoculating, plates should be brought to room temperature.
- As soon as possible after collecting the specimen, innoculate it and streak it.
- If the specimen is to be cultured on a swab then roll the swab across a small area of the surface of the agar.
- Streak for isolation using a sterile loop
- For 18-24 hours, incubate plates at 35-37degC. Some organisms may require more time for visible growth.
- Investigate the morphology of colonial cells.
Result Interpretation on Tryptic Soy Agar (TSA)
| Organisms | Growth |
| Aspergillus brasiliensis | Positive |
| Candida albicans | Positive |
| Staphylococcus aureus | Positive; pigmented shiny round colonies |
| Staphylococcus epidermidis | Positive |
| Bacillus subtilis | Positive; flat, large irregular colonies |
| Pseudomonas aeruginosa | Positive |
| Escherichia coli | Positive; shiny round colonies |
| Salmonella Typhimurium | Positive |
Uses of Tryptic Soy Agar (TSA)
- This medium can be used for many purposes, including culture storage, counting cells, isolation of pure cultures or general culture.
- Tryptic Soy Agar supports the development of many organisms, including fastidious and not-fastidious like Neisseria and Listeria and Brucella.
- For the cultivation of Salmonella Typhi, tryptone soya broth with sodium chloride and added dextrose.
- TSA is often used as the base medium for other types of agar plates. Blood agar plates (BAP), for example, are made by enriching TSA plates in defibrinated sheep’s blood. Chocolate agar is created through further cooking of BAP.
- It can be used for determining the X, V and XV factors in Hemophilus species by using strips that contain the factors V, XV and XV on the inoculated plates.
- The addition of salt to tryptic soyagar can help determine the halotolerance levels of microorganisms.
- It is used in pharmaceutical testing.
- It can be used to test water, cosmetics and industrial food.
- You can also use Tryptic Soy Agar as a medium to maintain or subculturing reference species, e.g. Enterobacteriaceae or staphylococci.
Limitations of Tryptic Soy Agar
- For complete identification, it is recommended that colonies grown from pure culture be subject to biochemical, immunological and molecular testing.
- Because it doesn’t promote certain types of fastidious bacteria, tryptic soyagar is not recommended for microbiology.
- It can’t be used to isolate pathogens in clinical specimens.
