Dehydrated culture media
Tryptose Soy Agar ISO
For the detection and enumeration of E. coli in water.
- Cat. No.
- LC-1138
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- ISO 9308
Tryptone Soy Agar is used for the quick and standard test for the detection and count of E. coli and other coliforms by the membrane filter technique as directed by ISO 9308-1.
Key features
Applications
Detection and non-selective enumeration of coliforms and Escherichia coli.
Industry
Water.
Standards
ISO 9308.
Preparation
40 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
It is also a general-purpose solid medium, particularly useful for the isolation, sensitivity testing and determination of hemolysis with fastidious microorganisms as it does not contain any sugars. Another use of the Tryptone Soy Agar is for the oxidase test according to the traditional method as described in ISO 9308-1.
Casein and soy peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride maintains the osmotic balance and bacteriological agar is the solidifying agent.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber, slightly opalescent |
| Final pH (25 °C) | 7.2 ± 0.1 |
| Amount per litre | 40 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bacteriological agar | 15 |
| Sodium chloride | 5 |
| Soy peptone | 5 |
| Tryptic digest of casein | 15 |
Preparation and use
Preparation
Suspend 40 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to 50 °C, mix well and dispense into plates.
According to ISO 9308
For the enumeration of E. coli and other coliform bacteria according to ISO 9308:
- Filter 100 mL of the sample through a membrane.
- Place the filter on a plate of Chromogenic E. coli Coliforms Agar (CCA) (LC-2080).
- Invert the plate and incubate at 36 ± 2 °C for 21 ± 3 hours.
- Count beta-D-galactosidase-positive colonies (pink to red) as presumptive coliform bacteria other than E. coli.
To avoid possible false positive results, caused by oxidase-positive bacteria such as Aeromonas spp., confirm the bacterial colonies through the oxidase test. Coliforms will be those that have an oxidase-negative result.
- Count the beta-D-galactosidase- and beta-D-glucuronidase-positive (dark blue to violet) colonies as E. coli.
- If the colonies have not grown adequately to perform the oxidase test with pure colonies, it is necessary to subculture them in a non-selective medium such as Tryptone Soy Agar (TSA).
- Incubate plates in inverted position at 36 ± 2 °C for 21 ± 3 hours.
The total coliform count is the sum of oxidase-negative colonies, beta-D-galactosidase-positive colonies (pink to red) and all colonies that are dark blue to violet.
Quality control
Microbiological test
Incubation conditions: 36 ± 2 °C / 21 ± 3 h.
| Microorganism | Specification |
|---|---|
| Klebsiella pneumoniaeATCC 13833 | Good growth |
| Escherichia coliATCC 25922 | Good growth |
Bibliography
- ISO 9308-1 Water quality. Detection and enumeration of Escherichia coli and coliform bacteria. Part 1: Membrane filtration method.
- Regulation water quality - Detection and count of Escherichia coli and coliform bacteria. Anon. 1987 J. Food Microbiol., 5: 291-296.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
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Tracked shipment
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Frequently asked questions
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