VRBG Agar (NutriSelect Plus) is formulated according to the requirements of the Harmonized Pharmacopeia (USP, EP, JP) and ISO 21152. The medium utilizes the inhibitory action of crystal violet and bile salts to suppress Gram-positive bacteria. Enterobacteriaceae degrade glucose, producing acid which causes the pH indicator (neutral red) to turn the colonies purple-pink to reddish-purple. These colonies are typically surrounded by a halo of precipitated bile salts. As a part of the NutriSelect® Plus line, this medium undergoes extensive quality testing to ensure high performance and consistency.
Advantages
- Broad Detection: Specifically designed to detect all members of the Enterobacteriaceae family, not just lactose fermenters.
- High Selectivity: Effective suppression of Gram-positive organisms and non-target microflora.
- Regulatory Compliance: Meets international standards including ISO 21528 and various Pharmacopoeias.
- NutriSelect® Plus Quality: Premium-grade ingredients for superior batch-to-batch reproducibility.
- Clear Visualization: Sharp color contrast between the red-purple colonies and the surrounding medium allows for easy counting.
Interpretation of Results
| Microorganism |
Colony Appearance |
| Escherichia coli |
Purple-pink colonies with a reddish halo |
| Salmonella typhimurium |
Purple-pink colonies with a reddish halo |
| Staphylococcus aureus |
Inhibited (No growth) |
| Pseudomonas aeruginosa |
Colorless to grey colonies (if growth occurs) |
Technical specifications
| Catalogue number |
70189 |
| Brand / Product Line |
Sigma-Aldrich / NutriSelect® Plus |
| Compliance |
ISO 21528, USP/EP/JP |
| Typical Composition (g/L) |
Yeast extract (3.0); Pancreatic digest of gelatin (7.0); Bile salts (1.5); Glucose (10.0); NaCl (5.0); Neutral red (0.03); Crystal violet (0.002); Agar (12.0) |
| pH (at 25 °C) |
7.4 ± 0.2 |
| Preparation |
38.53 g/L |
| Storage Temperature |
15 – 25 °C |
Available packaging options
| 70189-500G |
500 g plastic bottle |
