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Material Safety Data Sheet

Organisms

Organisms this product works with:

Dehydrated Culture Media

TETRATHIONATE BROTH (USA)

Code: CM0671

An American formulation which complies with the description given in the US Pharmacopoeia for the enrichment of specimens undergoing examination for salmonellae.

Typical Formula*

gm/litre

Casein peptone

2.5

Meat peptone

2.5

Bile salts

1.0

Calcium carbonate

10.0

Sodium thiosulphate

30.0

* Adjusted as required to meet performance standards 

Directions
Suspend 46g in 1 litre of distilled water and bring to the boil. Cool to below 45°C and add 20ml of iodine-iodide solution immediately before use. Mix continuously whilst dispensing 10ml volumes into sterile tubes. Use the complete medium (with added iodine) on the day of preparation.

Iodine-Iodide Solution

Iodine

6g

Potassium iodide

5g

Distilled water

20ml

The base may be prepared beforehand and kept for several weeks at 4°C. Iodine-iodide solution can then be added at the time of use to the quantity of medium needed.

Description
Tetrathionate Broth USA complies with the description given in the United States Pharmacopoeia1.

Tetrathionate Broth is specified by the 15th edition of Standard Methods for the Examination of Water and Wastewater2 and Compendium of Methods for the Microbiological Examination of Foods3 for the enrichment of specimens undergoing examination for salmonellae.

The selectivity of the medium depends on the ability of thiosulphate and tetrathionate in combination to suppress commensal coliform organisms4. Organisms which possess the enzyme tetrathionate reductase grow in the medium. Salmonella and Proteus species possess the enzyme; Escherichia coli and shigellae do not.

Proteus can be suppressed by adding 40mcg/ml of novobiocin6 to the incomplete medium before the addition of iodine.
Bile salts are present to inhibit those organisms which do not live in the intestine.

Brilliant Green 0.001% w/v can be added to the broth1 but it should be remembered that Salmonella typhi and some other salmonellae are inhibited by this compound.

The role of calcium carbonate is to neutralise the acidic tetrathionate decomposition products.

Technique
Inoculate the broth with 1-2g of the specimen and mix thoroughly to disperse the sample.
Incubate at 35°C and sub-culture after 18-24 hours to XLD Agar CM0469, SS Agars CM0099 or CM0533, Bismuth Sulphite Agar CM0201, or similar selective/indicator media for salmonella isolation.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the base broth at 2-8°C. Use the medium immediately after adding the iodine solution.

Appearance
Dehydrated medium: White coloured, free-flowing powder
Prepared medium: Off white coloured solution

Quality control

Positive control:

Expected results

Salmonella typhimurium ATCC® 14028

Good growth

Negative control:

 

Escherichia coli ATCC® 25922 *

No growth

* This organism is available as a Culti-Loop®

References
1. United States Pharmacopoeia USP 28 2005.
2. American Public Health Association (1998) Standard Methods for the Examination of Water and Wastewater. 20th Edn. APHA Inc. Washington DC.
3. American Public Health Association (2001) Compendium of Methods for the Microbiological Examination of Foods. 4th Edition APHA Inc.
Washington DC.
4. Pollock M. R. and Knox R. (1943) Biochem. J. 37. 476-481.
5. Papavassiliou J., Samaraki-Lyberopoulou V. and Piperakis G. (1969) Can. J. Microbiol. 15. 238-240.
6. Jeffries L. (1959) J. Clin. Path. 12. 568-571.

 
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