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Specifications:
| Application | Microbiology | ||
| Storage Temperature | Ambient | ||
| Product Type | Culture Medium | Forms | Powder |
| Product Brand | Liofilchem | ||
| Product Grade | Microbiology grade | ||
Medium for Differentiation of Enterobacteria via Phenylalanine Deaminase Activity
Liofilchem® Phenylalanine Agar is a selective culture medium used to differentiate Proteus, Providencia, and Morganella spp. from other members of the Enterobacteriaceae based on the activity of the phenylalanine deaminase enzyme. This medium is essential in clinical microbiology labs for identifying organisms that can oxidatively deaminate phenylalanine into phenylpyruvic acid.
Principle of the Method
This test relies on the enzymatic conversion of DL-phenylalanine to phenylpyruvic acid by phenylalanine deaminase. After incubation, the addition of 10% ferric chloride and 0.1 N HCl reacts with phenylpyruvic acid to form a green-colored complex, indicating a positive result. Absence of green coloration denotes a negative result.
Color Indicators:
- Positive: Green coloration after adding FeCl₃/HCl
- Negative: No color change (stays amber/yellowish)
Composition (per liter of medium)
| Component | Concentration (g/L) |
|---|---|
| Yeast Extract | 3.0 |
| Disodium Phosphate | 1.0 |
| Sodium Chloride | 5.0 |
| DL-Phenylalanine | 2.0 |
| Agar | 15.0 |
| Final pH at 25°C | 7.3 ± 0.2 |
Preparation Instructions
- Suspend 26.0 g of powder in 1 L of distilled or deionized water.
- Heat to dissolve completely.
- Dispense into tubes and autoclave at 121 °C for 15 minutes.
- Allow to solidify in a slanted position.
Test Procedure
- Inoculate the surface of the slant with a pure culture.
- Incubate at 36 ± 1°C for 18–24 hours.
- Add 3–5 drops of 10% ferric chloride (Code 80272) and 3–5 drops of 0.1 N hydrochloric acid.
- Rotate tube gently to moisten the culture.
- Observe for green coloration within 1–5 minutes.
Interpretation of Results
| Microorganism | Growth | Reaction |
|---|---|---|
| Escherichia coli ATCC 25922 | Good | Negative (-) |
| Enterobacter aerogenes 13048 | Good | Negative (-) |
| Proteus mirabilis ATCC 25933 | Good | Positive (+) |
| Proteus vulgaris ATCC 13315 | Good | Positive (+) |
Quality Control
Dehydrated Medium:
- Appearance: Homogeneous, free-flowing powder
- Color: Light tan
Prepared Medium:
- Appearance: Slightly opalescent, no precipitate
- Color: Light amber
Incubation Conditions:
- 36 ± 1 °C for 18–24 hours
Storage and Stability
| Form | Condition | Shelf Life |
|---|---|---|
| Dehydrated powder | 10–30 °C (dry) | As per expiry date on label |
| Prepared slants | 2–8 °C | Until expiration or contamination |
Applications
- Differentiation of Proteus, Providencia, and Morganella spp.
- Diagnostic tool in medical and veterinary microbiology
- Used in clinical labs for enterobacteria screening
Ordering Information
| Product | Catalogue No. | Pack Size |
|---|---|---|
| Phenylalanine Agar | 610039 | 500 g (for 19.2 L) |
| Phenylalanine Agar | 620039 | 100 g (for 3.8 L) |
References
- Ann. Inst. Pasteur. (1954) 87: 375-386.
- Public Health Lab. (1957) 15: 153.
Liofilchem® Phenylalanine Agar is a robust medium for detecting phenylalanine deaminase activity, providing clear, rapid differentiation of key members of the Proteae tribe within Enterobacteriaceae. With reliable colorimetric detection and standard preparation protocols, it is a critical tool in the microbiologist’s repertoire for bacterial identification.
- Pack Size: 100g 500g