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Thermo Scientific™ Oxoid™ Urea Agar Base (Dehydrated)
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Specifications:
| Application | Microbiology | ||
| Storage Temperature | Room Temperature | ||
| Product Type | Culture Medium | Forms | Powder |
| Product Brand | Thermo Fisher Scientific™ | ||
| Product Grade | Microbiology grade | Formula | For 20.8L medium |
The Thermo Scientific™ Oxoid Urea Agar Base (Dehydrated) is a high-quality culture medium designed for detecting urease activity in microorganisms, particularly Proteae and some Enterobacteriaceae. When used with a sterile 40% urea solution, it forms Christensen's medium, which is effective for the rapid detection of urease-positive organisms.
Key Features
- Rapid Detection: Detects urease activity in Proteae within 3-5 hours.
- Versatile Applications: Suitable for urease-positive Proteae and other Enterobacteriaceae (requires 24-48 hours for non-rapid urease activity).
- Color Change Indicator: Phenol red in the medium changes from orange to pink when urease-positive organisms hydrolyze urea, producing ammonia.
- Ease of Preparation: Requires the addition of sterile 40% urea solution to the base after autoclaving.
Typical Composition (g/L)
| Component | Amount (g/L) | Function |
|---|---|---|
| Peptone | 1.0 | Provides essential nitrogen and growth factors. |
| Glucose | 1.0 | Energy source for microbial metabolism. |
| Sodium Chloride | 5.0 | Maintains osmotic balance. |
| Disodium Phosphate | 1.2 | Acts as a buffer to maintain pH stability. |
| Potassium Dihydrogen Phosphate | 0.8 | Secondary buffer to support pH maintenance. |
| Phenol Red | 0.012 | pH indicator for urease activity (orange to pink). |
| Agar | 15.0 | Solidifying agent. |
Final pH: 6.8 ± 0.2
Preparation Instructions
- Suspend 2.4 g of dehydrated medium in 95 mL of distilled water.
- Bring to a boil to dissolve completely.
- Autoclave at 115°C for 20 minutes.
- Cool the medium to 50°C and aseptically add 5 mL of sterile 40% Urea Solution (SR0020).
- Mix thoroughly and distribute 10 mL into sterile containers.
- Allow the medium to solidify in the slope position.
Storage and Shelf Life
- Dehydrated Medium: Store at 10-30°C. Use before the expiration date on the label.
- Prepared Medium: Store at 2-8°C. Avoid heating or reheating to prevent urea decomposition.
Appearance
| State | Description |
|---|---|
| Dehydrated Medium | Straw-colored, free-flowing powder. |
| Prepared Medium | Orange-colored gel. |
Quality Control
| Control Type | Organism | Expected Results |
|---|---|---|
| Positive Control | Proteus mirabilis ATCC® 29906* | Urease positive; pink slope. |
| Negative Control | Escherichia coli ATCC® 25922* | Urease negative; no color change. |
*These control organisms are available as Culti-Loop® strains.
Precautions
- Ensure the reaction is read within 2-5 hours for Proteae; prolonged incubation may produce false-positive results due to non-urease alkaline reactions.
- Do not reheat the medium after preparation to avoid urea decomposition.
- Confirm urease activity by testing with a medium without urea as a control.
Applications
- Urease Detection: Ideal for rapid detection of urease-positive organisms, such as Proteae.
- Differentiation: Useful for identifying non-rapid urease activity in other Enterobacteriaceae.
- Clinical Diagnostics: Supports workflows in diagnostic microbiology for urinary tract pathogens and other urease-positive microbes.
Reference
- Christensen, W. B. (1946). Journal of Bacteriology, 52, 461-466.
The Thermo Scientific™ Oxoid Urea Agar Base is a reliable and versatile tool for microbiological diagnostics, ensuring accurate and rapid identification of urease-positive organisms.