Description
Levine EMB Agar for Coliform Isolation and Differentiation
Levine EMB Agar serves as an important medium for the isolation and differentiation of coliform bacteria, especially E. coli. This agar is widely utilized in microbiology laboratories for testing water, food, and clinical samples. Its unique formulation promotes the growth of lactose fermenters while effectively inhibiting certain gram-positive bacteria.
Key Ingredients
| Ingredients | gm/liter |
|---|---|
| Pancreatic Digest of Gelatin | 10.0 |
| Lactose | 10.0 |
| Dipotassium Hydrogen Phosphate | 2.0 |
| Agar | 15.0 |
| Eosin Y | 0.40 |
| Methylene Blue | 0.065 |
| Final pH | 7.1 ± 0.2 at 25°C |
Principle and Interpretation
The combination of Eosin Y and Methylene Blue acts as both a selective and differential agent. These dyes inhibit gram-positive bacteria while allowing for the clear identification of lactose fermenters. Consequently, at acidic pH, these dyes form a complex that enhances their inhibitory effect. Notably, E. coli colonies typically exhibit a green metallic sheen, which indicates strong lactose fermentation. This visual cue proves vital for microbiologists, ensuring they can easily identify and differentiate E. coli.
Preparation Instructions
To prepare the medium, follow these steps:
- Suspend 37.4g of Levine EMB Agar in 1 liter of distilled or deionized water.
- Mix well and heat with frequent agitation to ensure complete dissolution.
- Sterilize the mixture in an autoclave at 121°C (15 lbs.) for 15 minutes.
Appearance
- Dehydrated Medium: The powder appears as a free-flowing purplish red substance.
- Prepared Medium: After preparation, the gel presents a purplish red-brown color.
Storage Conditions
You should store the tightly capped container in a cool place, ideally between 5-30°C. The dehydrated medium remains stable for 3 years from the date of manufacture. Additionally, you can keep the prepared medium at 2-8°C, away from direct light to maintain its quality.
Quality Control
To ensure optimal performance, inoculate the prepared medium and incubate at 30-35°C for 24-48 hours. This step verifies the reliability of the medium for various applications, including clinical diagnostics, food analysis, and environmental testing.
Conclusion
In summary, Levine EMB Agar is a critical tool for anyone involved in microbiological testing, particularly for coliform isolation and differentiation. Its selective properties, ease of preparation, and clear visual indicators make it a preferred choice for reliable results across diverse applications. By integrating this medium into your processes, you can effectively identify E. coli and other lactose fermenting bacteria, enhancing your laboratory’s overall efficiency.
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