Dehydrated culture media
Schubert Broth
Coliform confirmatory medium, especially E. coli.
- Cat. No.
- LC-1282
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
Schubert Broth is used to confirm the presence of coliforms and Escherichia coli. Biochemical tests are carried out in the same tube: fermentation of mannitol and indole production, which provides a saving of time, handling and space. The tubes with turbidity associated with the production of gas are considered positive.
Key features
Applications
Detection of Escherichia coli.
Industry
Food.
Preparation
31.5 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Indole production can be shown by adding one or two drops of Kovac's Reagent. Kovac's Reagent detects the microorganisms capable of cleaving the tryptophan. When these microorganisms are present in the medium they liberate indole that reacts with 4-dimethylaminobenzaldehyde to form a dark red dye.
Peptone and tryptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Mannitol is the fermentable carbohydrate providing carbon and energy. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Magnesium sulfate and ammonium sulfate are ions required in a big variation of enzymatic reactions, including DNA replication. Sodium citrate partially or completely inhibits Gram-positive organisms, coliforms and Proteus. The addition of tryptophan to the medium allows the performance of the indole test for further E. coli confirmation.
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) | 7.6 ± 0.2 |
| Amount per litre | 31.5 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Ammonium sulfate | 0.4 |
| L-Glutamic acid | 0.2 |
| Magnesium sulfate | 0.7 |
| Mannitol | 7.5 |
| Peptone | 10 |
| Sodium chloride | 2 |
| Sodium citrate | 0.5 |
| Tryptone | 10 |
| Tryptophan | 0.2 |
Preparation and use
Preparation
Suspend 31.5 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. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.
Instructions for use
- Inoculate an isolated colony in the tube of Schubert Broth.
- Incubate at a temperature of 44 °C for 24 hours.
- For the indole test, add 3 to 4 drops of Kovac's Reagent (LC-5205), and shake the tube gently.
- The appearance of red or pink color in the reagent layer is a positive indication of indole.
Quality control
Microbiological test
Incubation conditions: 44 °C / 24 h.
| Microorganism | Specification | Characteristic reaction |
|---|---|---|
| Escherichia coliATCC 25922 | Good growth | Indole (+) |
| Staphylococcus aureusATCC 25923 | Inhibited growth | |
| Enterococcus faecalisATCC 29212 | Inhibited growth | |
| Escherichia coliATCC 8739 | Good growth | Indole (+) |
Bibliography
- Mackenzie E.F.N., Taylor E.N. and Gilbert W.E. 1948. Recent experiences in the rapid identification of E. coli, type I. J. Gen. Microbiol. 2:197-204.
- Fennel H. 1972. A single tube confirmatory test for E. coli at 44 °C. Proc. Soc. Wat. Treatm. Exam. 21:13-20.
- Oger C. and Leclerc H. 1977. Essais de nouveaux tests "haute température" pour mise en évidence des coliformes fécaux ou des Escherichia coli dans les eaux. Microbia. 3:47.
- AFNOR. T90-413. Octobre 1985. Essais des eaux - Recherche et dénombrement des coliformes et des coliformes thermo-tolérants. Méthode générale par ensemencement en milieu liquide (NPP).
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