Soyabean Casein Digest Agar also know as Tryptone Soya Agar or broth (TSA) is a general purpose growth media used for the culture of a wide variety of microorganisms including fastidious organism like Neisseria species,Brucella,Haemophilus species and Listeria etc . With an addition of blood,this media becomes perfectly adapted for the detection of hemolysis and also prevent the lysis of erythrocytes due to the presence of sodium chloride. TSA is used for a wide range of application in a medical laboratory especially for isolation of pure cultures,counting and stock culture (Culture storage).
Principle of Tryptone Soya Agar
- This media is very nutritious due to the combination of tryptone and soya peptone which provide amino acids and long chain peptides for the growth of variety microorganisms.
- The presence of sodium chloride is to maintains the osmotic balance.
- While soyabean Casein Digest Agar does not contains X and V growth factors. It can be conveniently used in determining the requirements of these growth factors by isolates of Haemophilus by the addition of X-factor( hemin) , V-factor, and X+V factor discs factor to inoculated TSA plates
Composition of Tryptone Soya Agar
The following ingredients are used for the composition Tryptone soya agar
|Final pH temperature at 25°C||7.3±0.2|
How to Prepare Tryptone Soya Agar
The preparation of Tryptone Soya Agar depends on each laboratory workload or the numbers of culture plates available. Anyway, note that a standard Petri dish is equivalent to 20ml when poured completely.
- Start by suspending 40 grams in 1000 ml distilled water.
- Now heat to boiling to dissolve the medium completely.
- Follow by sterilization by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
For more selectivity if desired, aseptically add 5% v/v defibrinated blood in previously cooled medium to 45-50°C for cultivation.
- Mix well and pour into sterile Petri plates.
NB: It is also advisable to incubate a petri dish for 24 hour for quality control in order to avoid wastage of resources and ease early detection of contamination after the preparation.
Appearance of Medium after preparation
- Normal or basal Medium will appear : Light yellow coloured clear to slightly opalescent gel.
- Basal medium + 5-7%w/v sterile defibrinated blood will appear : Cherry red coloured opaque gel forms in Petri plates
Type of Inoculums
With Addition of blood
- water samples
Without addition of blood
- Pharmaceutical samples
Plate reading and Colonies morphology on Tryptone Soya Agar after an incubation for Bacterial at temperature 30-35°C for 18-24 hours and for Fungal at 30-35°C for 5 days
|Bacillus subtilis ATCC 6633||Growth no haemolysis|
|Staphylococcus aureus ATCC 25923||Growth beta haemolysis|
|Escherichia coli ATCC 25922||Growth no haemolysis|
|Pseudomonas aeruginosa ATCC 27853||Growth-|
|Salmonella Abony NCTC 6017||Growth-|
|Micrococcus luteus ATCC 9341||Growth-|
|Streptococcus pneumoniae ATCC 6305||Growth; alpha hemolysis|
|Salmonella Typhimurium ATCC 14028||Growth-|
|Enterococcus faecalis ATCC 29212||Growth-|
|Candida albicans ATCC 10231||Growth-|
|Aspergillus brasiliensis ATCC 16404||Growth-|
|Clostridium perfringens ATCC 13124||Growth-|
This medium is general purpose medium and may not support the growth of fastidious organisms without an addition of blood
- The United States Pharmacopoeia , 2018, The United States Pharmacopoeial Convention Inc., Rockville, MD.
- Jorgensen,J.H., Pfaller , M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015)Manual of Clinical Microbiology, 11th Edition. Vol. 1.
- Gunn B. A., Ohashi D K., Gaydos C. A., Holt E. S., 1977, J. Clin. Microbiol., 5(6) : 650
- Forbes B. A., Sahm A. S. and Weissfeld D. F., 1998, Bailey and Scotts Diagnostic Microbiology, 10th Ed., Mosby Inc.
St. Louis, Mo
- Indian Pharmacopoeia, 2018, Govt. of India, Ministry of Health and Family Welfare, New Delhi, India.
- Isenberg, H.D. Clinical Microbiology Procedures Handbook. 2nd Edition.