Ready-to-use media
Lauryl Sulfate Broth (Lauryl Tryptose Broth - LTB) C+ ISO
Liquid medium used for the detection and enumeration of coliform bacteria according to IDF-FIL 73B and ISO Standards.
- Cat. No.
- LC-4040
- Category
- Ready-to-use media
- Format
- 20 tubes
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 4 months
- Standards
- ISO 4831ISO 7251
Lauryl Sulfate Broth is used for the MPN presumptive test of coliforms in water and sewage, confirmatory test of lactose fermentation with gas production for milk and detection of coliforms in food.
Key features
Applications
Detection and selective enumeration of coliforms and Escherichia coli.
Industry
Dairy products, food.
Standards
ISO 4831, ISO 7251.
Presentation
20 tubes, 17 x 145 mm, with 10 ± 0.2 mL.
Description and technique
Description
The high nutrient quality and the presence of phosphate buffer in this medium ensure rapid growth and increased gas production, even by slow lactose-fermenting coliforms.
Indole production is observed by adding a few drops of Kovac's Reagent to the broth (with or without previous extraction) and shaking gently. Formation of a red ring indicates indole production.
Technique
Collect, dilute and prepare samples and volumes as required according to specifications, directives, official standard regulations and/or expected results. Dispense liquid medium in appropriate containers if the original container is of large volume.
Inoculate aseptically the tubes with the prepared sample or its dilution.
Incubate the tubes tightly closed aerobically at 35-37 °C for up to 48 hours.
Read the turbidity increase as growth indicator.
(Incubation times, temperature and sample volumes may vary depending on the sample, on the specifications, etc.)
Presumptive isolation/recovery of coliforms must be confirmed by further microbiological and biochemical tests. Lauryl sulphate largely inhibits the growth of undesired bacteria.
Each laboratory must evaluate the results according to their specifications.
Presentation
| Presentation | 20 tubes, 17 x 145 mm |
|---|---|
| Filling | 10 ± 0.2 mL |
| Packaging | 17 x 145 mm glass tubes, ink labelled, metal non-injectable cap. 20 tubes per box, with Durham tube. |
Composition
| Ingredient | g/L |
|---|---|
| Tryptose | 40.0 |
| Lactose | 10.0 |
| Sodium chloride | 10.0 |
| Dipotassium hydrogen phosphate | 5.5 |
| Potassium dihydrogen phosphate | 5.5 |
| Sodium lauryl sulfate | 0.2 |
Quality control
Physical/chemical control
| Color | Orange |
|---|---|
| pH | 6.8 ± 0.3 at 25 °C |
Microbiological control
Inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity) / 10⁴-10⁶ (selectivity).
Dilute to normal concentration.
Aerobiosis. Incubation at 37 ± 1 °C, reading after 24-48 ± 2 h.
| Microorganism | Growth |
|---|---|
| Escherichia coliATCC 25922, WDCM 00013 | Good - gas positive |
| Escherichia coliATCC 8739, WDCM 00012 | Good - gas positive |
| Citrobacter freundiiATCC 43864, WDCM 00006 | Good - gas positive |
| Enterococcus faecalisATCC 19433, WDCM 00009 | Inhibited - poor |
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- APHA AWWA WPCF (1995) Standard Methods for the examination of water and wastewater. APHA. Washington.
- DOWNES, F.P. & K. ITO (2001) Compendium of Methods for the Microbiological Examination of Food. 4th ed. APHA. Washington.
- FDA (Food and Drug Administration) (1998) Bacteriological Analytical Manual. 8th ed. Rev. A. AOAC International. Gaithersburg. MD.
- FIL IDF Standard 73B (1998) Milk and milk products. Enumeration of coliforms. IDF. Brussels.
- HORWITZ, W. (2000) Official methods of Analysis. 17th ed. AOAC International. Gaithersburg. MD.
- ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
- ISO 4831 Standard (1991) General guidance for the enumeration of coliforms - MPN technique.
- ISO 7251 Standard (1993) General guidance for enumeration of E. coli by MPN technique.
- MARSHALL R.T. (1992) Standard Methods for the examination of dairy products. 16th ed. APHA. Washington.
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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