Description

INTENDED USE

Tryptic (Trypticase) Soy Agar (TSA) is used for the isolation and cultivation of nonfastidious and fastidious microorganisms. It is not the medium of choice for anaerobes.

SUMMARY AND EXPLANATION

The nutritional composition of TSA has made it a popular medium for many years. It is the medium specified as Soybean- Casein Digest Agar Medium in General Chapter <61> of the USP when performing enumerations tests for nonsterile pharmaceutical products. The medium is used in USP Growth Promotion testing and when testing the suitability of counting methods in the presence of product. TSA has a multitude of uses in the clinical laboratory including maintenance of stock cultures, plate counting, isolation of microorganisms from a variety of specimen types and as a base for media containing blood. It is also recommended for use in industrial applications when testing water and wastewater, food, dairy products, and cosmetics.

Since TSA does not contain the X and V growth factors, it can conveniently be used in determining the requirements for these growth factors by isolates of Haemophilus by the addition of X, V and XV Factor Strips to inoculated TSA plates.

PRINCIPLE

The combination of casein and soy peptones in TSA renders the medium highly nutritious by supplying organic nitrogen, particularly amino acids and longer-chained peptides. The sodium chloride maintains osmotic equilibrium. Agar is the solidifying agent.

Haemophilus species may be differentiated by their requirements for X and V factors. Paper strips impregnated with these factors are placed on the surface of the medium after inoculation with the test organism. Following incubation, a zone of growth around the strip indicates a requirement for the factor(s).