This medium is based on the formulation of Lauryl Tryptose Broth but solidified with agar for colony enumeration. The selectivity is primarily due to Sodium Lauryl Sulfate, a surface-active agent that effectively inhibits the growth of Gram-positive bacteria and most non-coliform organisms without hindering the development of the Enterobacteriaceae family. Tryptose provides a rich source of nitrogen, vitamins, and minerals. Lactose is included as the fermentable carbohydrate. When used with a pH indicator (such as Bromocresol Purple or through secondary testing), the fermentation of lactose by coliforms results in acid production. Sodium Chloride maintains the osmotic balance of the medium, ensuring the recovery of stressed cells.
Advantages
- High Selectivity: Sodium Lauryl Sulfate provides a robust barrier against Gram-positive contaminants, reducing false positives.
- Standardized Testing: Widely used in environmental and food microbiology for the presumptive stages of coliform testing.
- Colony Counting: The agar format allows for the direct enumeration of Colony Forming Units (CFU), providing quantitative data on contamination levels.
- Reduced Toxicity: Unlike some bile-based media, the concentration of lauryl sulfate is carefully balanced to be highly selective yet minimally inhibitory to injured coliforms.
- Versatile Application: Suitable for testing a wide variety of samples, from clear water to complex food matrices.
Technical specifications
| Catalogue number |
1309 |
| Brand |
Condalab |
| Application |
Detection and enumeration of coliforms |
| Typical Composition (g/L) |
Tryptose (20.0); Lactose (5.0); Sodium Chloride (5.0); Sodium Lauryl Sulfate (0.1); Bacteriological Agar (14.6) |
| Final pH (at 25 °C) |
6.8 ± 0.2 |
| Preparation |
44.7 g/L |
| Storage Temperature |
2 – 25 °C |
Available packaging options
| 1309 |
500 g plastic bottle |
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