VRBL Agar is designed to selectively isolate coliforms while providing a clear visual differentiation of lactose fermenters. The Peptone Mixture and Yeast Extract serve as the primary sources of nitrogen, vitamins, and minerals. Selectivity is achieved through the inclusion of Bile Salts No. 3 and Crystal Violet, which effectively inhibit the growth of Gram-positive bacteria. The differential principle is based on the fermentation of Lactose. When coliforms ferment lactose, they produce acid, causing the Neutral Red indicator to turn the colonies dark red or purple. These colonies are typically surrounded by a characteristic halo of precipitated bile salts. The medium is traditionally used with an overlayer technique to ensure semi-anaerobic conditions, which suppresses the growth of non-target Gram-negative flora and improves the definition of the red halos.
Advantages
- ISO 4832 Compliance: Formulated to meet the international standardized requirements for the horizontal method of coliform enumeration.
- High Selectivity: The combination of Crystal Violet and Bile Salts ensures minimal interference from Gram-positive microorganisms.
- Distinct Differentiation: Provides high-contrast, dark red colonies with bile precipitation zones, facilitating accurate manual and automated counting.
- Rapid Results: Allows for the presumptive identification of coliforms within 24 hours of incubation.
- Industry Standard: Widely adopted in dairy and food quality control laboratories for routine hygiene monitoring.
Technical specifications
| Catalogue number |
1093 |
| Brand |
Condalab |
| Application |
Enumeration of coliforms (ISO 4832) |
| Typical Composition (g/L) |
Peptone Mixture (7.0); Yeast Extract (3.0); Lactose (10.0); Sodium Chloride (5.0); Bile Salts No. 3 (1.5); Neutral Red (0.03); Crystal Violet (0.002); Bacteriological Agar (12.0) |
| Final pH (at 25 °C) |
7.4 ± 0.2 |
| Preparation |
38.53 g/L |
| Storage Temperature |
2 – 25 °C |
Available packaging options
| 1093 |
500 g plastic bottle |
