Lauryl Sulfate Tryptose Broth for Coliform and E. coli Detection

Description

Lauryl Sulfate Tryptose Broth Granule: For Coliform and E. coli Detection

Lauryl Sulfate Tryptose (LST) Broth Granule is a trusted microbiological medium designed to determine and enumerate coliform bacteria, particularly E. coli, in water, dairy products, and food samples. Its precise formulation ensures accurate results, making it an essential product for laboratories involved in food safety, water quality testing, and microbial analysis.

Composition and Key Ingredients

The specific formulation of Lauryl Sulfate Tryptose Broth supports the selective growth of coliforms while inhibiting non-coliform bacteria. This medium is carefully balanced to promote robust bacterial growth while inhibiting the growth of unwanted organisms. The ingredients include:

• Pancreatic Digest of Casein (20.0 g/L): Supplies nitrogen and carbon compounds essential for bacterial growth.
• Sodium Chloride (5.0 g/L): Maintains osmotic balance, ensuring bacterial cells remain healthy.
• Lactose (5.0 g/L): Serves as a fermentable carbohydrate, which coliforms, especially E. coli, utilize to produce gas.
• Dipotassium Phosphate (2.75 g/L) and Monopotassium Phosphate (2.75 g/L): Act as buffering agents to stabilize the medium’s pH.
• Sodium Lauryl Sulfate (0.1 g/L): Selectively inhibits the growth of non-coliform organisms, making the detection of coliforms more efficient.

The medium is adjusted to a final pH of 6.8 ± 0.2 at 25°C, ensuring an ideal environment for bacterial growth.

How to Prepare Lauryl Sulfate Tryptose Broth

To prepare Lauryl Sulfate Tryptose Broth Granule, follow these simple steps:

1. Suspend 35.6 grams of the medium in one liter of deionized or distilled water.
2. Mix the solution well and heat it slowly to dissolve the granules completely.
3. Dispense the medium into test tubes, adding gas collection tubes (Durham) for the detection of gas production by coliforms.
4. Sterilize the prepared medium in an autoclave at 121°C for 15 minutes at 15 lbs. pressure.

This process ensures that the medium is sterile and ready for coliform detection.

Principle of Lauryl Sulfate Tryptose Broth

LST Broth is specifically designed for coliform testing, particularly for detecting E. coli. The presence of tryptose in the medium provides essential nutrients such as nitrogen and carbon compounds, enabling robust bacterial growth. Coliform bacteria ferment lactose, which produces gas detectable in the Durham tubes. The sodium lauryl sulfate selectively inhibits non-coliform bacteria, allowing for the effective detection of coliforms even from small inoculums. Furthermore, the medium is effective in suppressing the growth of aerobic spore-formers, making it highly reliable for microbial testing.

For testing larger sample sizes (greater than 10 ml), double-strength or proportionally increased medium should be used to ensure accurate results.

Appearance and Quality Control

The dehydrated Lauryl Sulfate Tryptose Broth is a yellowish, free-flowing granule that forms a clear, pale yellow solution upon dissolution. It must undergo rigorous quality control measures, including inoculation and incubation at 36 ± 1°C for 24-48 hours. Positive results are indicated by gas formation in the Durham tubes, confirming the presence of coliform bacteria.

Storage and Shelf Life

To maintain its effectiveness, store Lauryl Sulfate Tryptose Broth Granule in its original, tightly sealed container between 5-30°C. When stored properly, the dehydrated medium has a shelf life of three years from the manufacturing date. Prepared medium can be stored at 2-8°C, out of direct light, to preserve its usability for future tests.

Why Use Lauryl Sulfate Tryptose Broth?

Lauryl Sulfate Tryptose Broth is ideal for laboratories that require precise and reliable methods to detect and enumerate coliform bacteria, particularly E. coli, in water, dairy, and food samples. Its carefully balanced composition supports robust bacterial growth while inhibiting non-coliform organisms. As a result, it is commonly used in water testing facilities, food safety labs, and environmental testing centers.

Precautions and Important Notes

This medium is strictly intended for laboratory use only. Always check for signs of caking or color variation in the dehydrated medium before use, as these are indicators of potential degradation. Expired or compromised medium should be discarded to ensure accurate testing results.

In conclusion, Lauryl Sulfate Tryptose Granule provides an efficient and reliable solution for detecting coliform bacteria, particularly E. coli, across a wide range of samples. Its precise formulation and easy preparation make it a go-to product for microbiologists and quality control professionals seeking consistent and accurate microbial analysis. By following recommended procedures and proper storage practices, this medium will offer dependable performance in any laboratory setting. visit our [Other Series] for more related products