Dehydrated culture media
Lactose Broth
For the detection of coliforms and pre-enrichment of Salmonella.
- Cat. No.
- LC-1206
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Also available
- Ready-to-use medium, 4 formats (LC-4208)
Lactose Broth is included in many Standard Methods for testing foods, dairy products and other materials for enterobacteria and other Gram-negative microorganisms. It is also widely used for testing for coliforms in water and foods.
Key features
Applications
Detection of coliforms and enrichment of Salmonella.
Industry
Food, water.
Preparation
13 g in one liter of distilled water; dissolve by heating, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
It is used as pre-enrichment for testing foods and dairy products for Salmonella, where conservation processes may have injured or reduced their numbers. Pre-enrichment in a non-selective medium allows for repair of cell damage, diluting toxic or inhibitory substances, and provides a nutritional base for Salmonella. A pre-enrichment medium provides a higher ratio of Salmonella to non-Salmonella organisms after incubation. Most non-Salmonella bacteria ferment lactose whilst Salmonella does not. As lactose is metabolized, the pH decreases creating a bacteriostatic effect on competing organisms.
Large water samples may require double-strength Lactose Broth to maintain the correct concentration of the medium.
Gelatin and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is a complex carbohydrate energy source.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber |
| Final pH (25 °C) | 6.9 ± 0.2 |
| Amount per litre | 13 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Beef extract | 3 |
| Gelatin pancreatic digest | 5 |
| Lactose monohydrate | 5 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
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. Dispense into tubes with Durham gas collecting tubes for gas detection. Sterilize in autoclave at 121 °C for 15 minutes. Cool as quickly as possible.
Instructions for use
- Check the sterilization of the medium by incubating the tubes at 35 °C for 24 hours prior to inoculation.
- Ensure that the fermentation tubes are free from air bubbles before inoculation.
- Seed aliquots of 1, 10 or 100 mL of the sample liquid in adequate containers according to the quantity of the medium.
- Incubate at 35 ± 2 °C for 18-24 hours and check for the presence of gas, which constitutes a presumptive coliform test.
- Subculture to VRBGL (LC-1144) for detection and quantification tests.
Quality control
Microbiological test
Incubation conditions: 35 ± 2 °C / 18-24 h.
| Microorganism | Specification | Characteristic reaction |
|---|---|---|
| Proteus vulgarisATCC 13315 | Good growth | Gas production (-) |
| Klebsiella pneumoniaeATCC 13883 | Good growth | Gas production (+) |
| Salmonella typhimuriumATCC 14028 | Good growth | Gas production (-) |
| Escherichia coliATCC 25922 | Good growth | Gas production (+) |
Bibliography
- European Pharmacopoeia, 6th Edition 2007
- American Public Health Association. Standard Methods of the Examination of Dairy Products, 12th Edition APHA, New York, 1967.
- American Public Health Association. Standard Methods for the Examination of Water and Wastewater Edition APHA, Inc. New York, 1966.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
Every lot comes with its certificate.
Tracked shipment
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Frequently asked questions
Can I ask for formats other than those listed?
Yes: custom formats and OEM packs are available on request. Tell us the quantities you need.
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