Dehydrated culture media
Lysine Decarboxylase Broth
For the identification of microorganisms, especially enteric bacilli, based on the decarboxylation of lysine.
- Cat. No.
- LC-1208
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- ISO 10273
- Also available
- Ready-to-use medium, 1 format (LC-4229)
Lysine Decarboxylase Broth is used to detect and differentiate enterobacteria from other microorganisms, based on lysine decarboxylation.
Key features
Applications
Differentiation of enterobacteria.
Industry
Food, water.
Standards
ISO 10273.
Preparation
14 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Gelatin peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Dextrose is the fermentable carbohydrate. Bromocresol purple is the pH indicator. Lysine is added to detect the production of the specific enzyme.
When the medium is inoculated with a bacterium that is able to ferment dextrose, the acid produced lowers the pH of the medium and changes the color of the indicator from purple to yellow. The acidic condition also stimulates decarboxylase activity. The bacteria that decarboxylate the L-lysine to cadaverine are identified by the presence of a purple-red color. The production of these amines elevates the pH of the medium. A yellow color after 24 hours indicates a negative result.
By substituting L-lysine with arginine or ornithine, the new resulting medium (Falkow Broth Base) can be used to study the decarboxylation of these amino acids.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Light beige |
| Color of the prepared medium | Violet |
| Final pH (25 °C) | 6.8 ± 0.2 |
| Amount per litre | 14 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bromocresol purple | 0.02 |
| Dextrose | 1 |
| Gelatin peptone | 5 |
| L-Lysine | 5 |
| Yeast extract | 3 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 14 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 quantities of 5 mL into screw-capped tubes. Sterilize in autoclave at 121 °C for 15 minutes. Leave caps loose to allow gas exchange. Close well after sterilization.
Instructions for use
- Gently insert the inoculation loop with the sample into the tube and move the loop back and forth several times to inoculate the medium.
- Incubate at 35 ± 2 °C for 24 hours.
- Color change to purple: positive decarboxylation reaction (Escherichia, Klebsiella, Salmonella except S. paratyphi, Arizona, Alkalescens-Dispar, Serratia).
- Yellow color: negative decarboxylation reaction (Proteus, Providencia, S. paratyphi A, Shigella, Aeromonas, Citrobacter).
Quality control
Microbiological test
Incubation conditions: 35 ± 2 °C / 18-48 h.
| Microorganism | Characteristic reaction |
|---|---|
| Proteus vulgarisATCC 13315 | Lysine decarboxylation (-) |
| Escherichia coliATCC 25922 | Lysine decarboxylation (+) |
| Serratia liquefaciensATCC 27592 | Lysine decarboxylation (+) slow |
| Salmonella paratyphiATCC 9150 | Lysine decarboxylation (-) |
Bibliography
- Falkow A. S. Clin. Path. 28:598, 1958.
- Ewing, Davis and Deaves, Studies in the Serratia Group. U.S. Dept. H.E.W., C.D.C. Atlanta, 1972.
- Edwards and Ewing. Identification of Enterobacteriaceae, Burgess Publ. Co. Minneapolis, Minn., 1961.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
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Frequently asked questions
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