tryptone soya agar (soybean casein digest agar) Principles,composition and growth characteristics

staphylococcus aureus on TSA

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

source site The following ingredients are used for the composition Tryptone soya agar

go to link Ingredients Grams/Litres
Tryptone15.000
Soya peptone5.000
Sodium chloride5.000
Agar15.000
Final pH temperature at 25°C7.3±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.
Also read  Pseudomonas aeruginosa : Morphology,Diagnosis and Cultural characteristics

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
Tryptone soya agar without blood
Tryptone soya agar without blood

Type of Inoculums

With Addition of blood

  • Blood
  • Urine
  • faeces
  • Foods
  • 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

Organisms Haemolysis
Bacillus subtilis ATCC 6633Growth no haemolysis
Staphylococcus aureus ATCC 25923Growth beta haemolysis
Escherichia coli ATCC 25922Growth no haemolysis
Pseudomonas aeruginosa ATCC 27853Growth-
Salmonella Abony NCTC 6017Growth-
Micrococcus luteus ATCC 9341 Growth-
Streptococcus pneumoniae ATCC 6305Growth; alpha hemolysis
Salmonella Typhimurium ATCC 14028 Growth-
Enterococcus faecalis ATCC 29212Growth-
Candida albicans ATCC 10231 Growth-
Aspergillus brasiliensis ATCC 16404Growth-
Clostridium perfringens ATCC 13124Growth-

Possible limitation

This medium is general purpose medium and may not support the growth of fastidious organisms without an addition of blood

Reference

  • 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.
Also read  Thiosulfate Citrate Bile Sucrose Agar ideal for vibrio species

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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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