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Violet Red Bile Agar (VRBA) | AS-1375 | Coliform Enumeration | AuSaMicS
$35.00 AUD
AuSaMicS Life Science • Selective Differential Agar for Coliform Enumeration
Violet Red Bile Agar (VRBA)
Violet Red Bile Agar is a selective differential medium used for enumeration of coliform bacteria in food and dairy microbiology. Bile salts and crystal violet suppress many Gram-positive organisms, while lactose fermentation and neutral red support recognition of typical coliform colonies.
Cat No.: AS-1375
Coliform AgarVRBAAustralian Stock
Format: Dehydrated culture medium Support: COA / technical support available
Application Summary
Professional laboratory use
Reliable workflow integration
Australian stock
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Overview & Applications
Violet Red Bile Agar is a selective differential medium used for enumeration of coliform bacteria in food and dairy microbiology. Bile salts and crystal violet suppress many Gram-positive organisms, while lactose fermentation and neutral red support recognition of typical coliform colonies.
Primary Applications
- Coliform enumeration in food and dairy products
- Routine hygiene and indicator organism monitoring
- Water and environmental testing workflows where validated
- Quality control laboratories and food safety programs
Key Features
- Classical medium for coliform counts
- Lactose fermentation-based readout
- Bile salts and crystal violet provide selectivity
- Widely recognized in food microbiology
Typical Composition / Product Characteristics
| Component / Attribute | Amount / Value | Function | Practical Role |
|---|---|---|---|
| Peptone | 7.0 g/L | Nutrient base | Supports growth of target bacteria |
| Yeast extract | 3.0 g/L | Growth factor source | Improves recovery |
| NaCl | 5.0 g/L | Osmotic balance | Maintains ionic strength |
| Bile salts | 1.5 g/L | Selective agent | Suppresses many Gram-positive organisms |
| Lactose | 10.0 g/L | Fermentable carbohydrate | Differentiates lactose fermenters |
| Neutral red | 0.03 g/L | pH indicator | Highlights acid-producing colonies |
| Crystal violet | 0.002 g/L | Selective dye | Improves selectivity |
| Agar | 15.0 g/L | Solidifying agent | Forms firm plate medium |
| Final pH | 7.4 ± 0.2 | Optimized condition | Supports selective differential performance |
Preparation, Incubation & Interpretation
Preparation
Prepare according to your validated VRBA method. Reconstitute the medium in purified water, heat to dissolve, and avoid excessive overheating. Follow the supplier-specific preparation instructions used in your QC system.
Incubation / Use
Incubation conditions depend on the regulatory method and sample type. Routine food microbiology protocols commonly use overnight incubation around 30–37°C.
Interpretation
Typical coliform colonies are red to purple, often with a surrounding precipitated bile zone. Colony morphology and count criteria should follow the validated laboratory method in use.
Comparative Media / Workflow Position
| Medium / Product | Primary Target | Principle | Typical Use | Key Advantage |
|---|---|---|---|---|
| VRBA | Coliform bacteria | Selective lactose differential agar | Food and dairy coliform counts | Classic coliform readout |
| VRBGA | Enterobacteriaceae | Selective glucose agar | Broader enterobacteria counts | Improved overall Enterobacteriaceae recovery |
| MacConkey Agar | Gram-negative enterics | Selective differential agar | Clinical and general enteric work | Broad enteric use |
| EMB Agar | Coliforms / enterics | Selective differential agar | Water and dairy applications | Distinct lactose-based colony appearance |
Recommended Workflow
1. Prepare sample dilutions
Homogenize and dilute according to the target method.
Homogenize and dilute according to the target method.
2. Plate onto VRBA
Use pour-plate or surface-plate technique as required.
Use pour-plate or surface-plate technique as required.
3. Incubate
Follow validated time/temperature conditions.
Follow validated time/temperature conditions.
4. Count typical colonies
Enumerate and confirm coliforms as required by the method.
Enumerate and confirm coliforms as required by the method.
Strategic Use
Advantages
- Established classical medium for coliform enumeration
- Easy visual recognition of lactose-fermenting colonies
- Suitable for food and dairy QC programs
Considerations
- More focused on coliforms than total Enterobacteriaceae
- Method conditions should match the applicable standard
- Some stressed organisms may need pre-enrichment or recovery support
Selection Guide
- Choose for traditional coliform counting workflows
- Good fit for food and dairy microbiology
- Use VRBG instead when broader Enterobacteriaceae recovery is required