Dehydrated culture media
Lactose Broth with Bromocresol Purple
For the presumptive detection of coliform bacteria in water.
- Cat. No.
- LC-1272
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
Lactose Broth with Bromocresol Purple is used for detection of the presence of coliform organisms in water and food, and for the determination of lactose-fermenting bacteria. It is commonly used with Durham fermentation tubes for the examination of gas formation.
Key features
Applications
Detection of coliforms.
Industry
Water.
Preparation
13 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Casein peptone and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. The fermentation of lactose is shown by the acidification of the medium that causes the pH indicator (bromocresol purple) to turn yellow, as well as by gas production in Durham tubes. E. coli and coliforms can ferment lactose with gas production and therefore the color of the medium changes to yellow.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Clear beige |
| Color of the prepared medium | Purple |
| Final pH (25 °C) | 6.7 ± 0.2 |
| Amount per litre | 13 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bromocresol purple | 0.03 |
| Casein peptone | 7 |
| Lactose | 5 |
| Beef extract | 1 |
Preparation and use
Preparation
Suspend 13 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 and dispense into tubes. Sterilize in autoclave at 121 °C for 15 minutes. Avoid overheating.
Instructions for use
- Take the inoculum with a sterile loop.
- Submerge the loop into the medium and shake gently.
- Incubate at 37 ± 2 °C for 18-24 hours.
Quality control
Microbiological test
Incubation conditions: 37 ± 2 °C / 18-24 h.
| Microorganism | Specification | Characteristic reaction |
|---|---|---|
| Enterococcus faecalisATCC 11700 | Good growth | Yellow/purple medium, gas (-) |
| Klebsiella pneumoniaeATCC 13883 | Good growth | Yellow medium, gas (+) |
| Salmonella typhimuriumATCC 14028 | Good growth | Purple medium, gas (-) |
| Escherichia coliATCC 25922 | Good growth | Yellow medium, gas (+) |
| Aeromonas hydrophilaATCC 7966 | Good growth | Purple medium, gas (-) |
Bibliography
- FDA (1998) Bacteriological Analytical Manual 8th ed. Rev. A. AOAC International. Gaithersburg, Va. USA.
- Downes, F.P. & K. Ito (2001) Compendium of methods for the microbiological examination of foods. 4th ed. APHA. Washington.
- European Pharmacopoeia (2005) 5th ed. § 2.6.13 Test for specified micro-organisms. EDQM. Council of Europe. Strasbourg.
What you receive
The product
Shipped under controlled temperature when the product requires it.
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