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Thermo Scientific™ Oxoid™ Vogel-Johnson Agar (Dehydrated), 500 g
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Specifications:
| Application | Microbiology | ||
| Storage Temperature | 2-8°C | ||
| Product Type | Culture Medium | Forms | Powder |
| Product Brand | Thermo Fisher Scientific™, Oxoid | ||
| Product Grade | Microbiology grade | ||
Thermo Scientific™ Oxoid™ Vogel-Johnson Agar is a selective and differential culture medium formulated to isolate and presumptively identify Staphylococcus aureus from clinical materials, food products, and heavily contaminated samples.
This medium is based on the United States Pharmacopoeia (USP) formula and supports the detection of coagulase-positive, mannitol-fermenting strains of S. aureus.
In this medium, Staphylococcus aureus reduces tellurite to metallic tellurium, producing distinct black colonies, while mannitol fermentation results in yellow zones around colonies due to the Phenol Red pH indicator.
Key Features
- Selective formulation: Contains potassium tellurite, lithium chloride, and glycine to inhibit non-target organisms.
- Differential medium: Detects S. aureus through mannitol fermentation and tellurite reduction.
- Distinct colony morphology: S. aureus appears as black colonies with yellow halos.
- USP-compliant formulation: Conforms to United States Pharmacopoeia XXI (1985) standards.
- High performance: Enables early detection of S. aureus from heavily contaminated food and clinical samples.
Principle
The selective agents—lithium chloride, glycine, and potassium tellurite—inhibit most contaminating organisms, allowing the growth of S. aureus.
The increased mannitol concentration (1% w/v) and Phenol Red indicator enable visual differentiation through fermentation reactions. S. aureus ferments mannitol, lowering the pH and turning the medium yellow around black colonies.
Composition (per liter, typical)
| Ingredient | Function |
|---|---|
| Peptone | Nitrogen, vitamins, and carbon source |
| Yeast extract | Growth factor and B-vitamin source |
| Mannitol | Carbohydrate source for fermentation |
| Lithium chloride | Selective agent |
| Glycine | Selective agent |
| Phenol red | pH indicator |
| Agar | Solidifying agent |
| Potassium tellurite (added separately) | Selective and differential agent |
Typical Formulation
| Parameter | Specification |
|---|---|
| Form | Dehydrated powder |
| Color | Light beige to pink-beige |
| pH at 25°C | 7.2 ± 0.2 |
| Final Medium Appearance | Red agar turning yellow around colonies due to mannitol fermentation |
Directions for Use
- Suspend 61.5 g of the dehydrated medium in 1 liter of distilled water.
- Heat to dissolve completely while stirring.
- Sterilize by autoclaving at 121°C for 15 minutes.
- Cool to 45–50°C and aseptically add 10 mL of 1% Potassium Tellurite Supplement (Liofilchem® REF. 80022).
- Mix thoroughly and pour into sterile Petri dishes.
- Inoculate and incubate at 36 ± 1°C for 24–48 hours.
Typical Results
| Organism | Colony Appearance | Mannitol Reaction |
|---|---|---|
| Staphylococcus aureus ATCC® 25923 | Black colonies with yellow halo | Positive |
| Staphylococcus epidermidis ATCC® 12228 | Small gray colonies, no halo | Negative |
| Escherichia coli ATCC® 25922 | Inhibited | — |
Product Specifications
| Parameter | Details |
|---|---|
| Product Name | Thermo Scientific™ Oxoid™ Vogel-Johnson Agar (Dehydrated) |
| Catalog Number | CM0641B |
| Form | Dehydrated powder |
| Quantity | 500 g |
| Yield | Approx. 8.2 L of medium |
| Storage Temperature | 10–30°C, dry environment |
| Product Type | Microbiology Agar Medium |
| Certifications/Compliance | Conforms to USP and FDA reference methods |
| Shelf Life | As indicated on the product label |
Applications
- Clinical Microbiology: Isolation of Staphylococcus aureus from swabs and wound specimens.
- Food Safety Testing: Detection of S. aureus in dairy, meat, baked goods, and processed foods.
- Environmental Monitoring: Analysis of contamination in food handling and processing environments.
- Pharmaceutical QC: Detection of coagulase-positive Staphylococcus in production areas.
Unique Advantages
- High selectivity and sensitivity for Staphylococcus aureus.
- Distinct black colony morphology simplifies presumptive identification.
- USP-compliant medium suitable for regulated environments.
- Compatible with Liofilchem® or Oxoid™ Potassium Tellurite Supplements.
- Reliable and reproducible performance for routine and confirmatory testing.
The Thermo Scientific™ Oxoid™ Vogel-Johnson Agar (Dehydrated, CM0641B) is a selective and differential agar medium that allows accurate and early detection of Staphylococcus aureus in food and clinical samples.
By combining tellurite reduction, mannitol fermentation, and selective inhibition of competing flora, this medium ensures consistent performance for diagnostic, food safety, and industrial microbiology laboratories.