Dehydrated culture media
Phenol Red Dextrose Agar
For the differentiation and confirmation of bacteria based on dextrose fermentation.
- Cat. No.
- LC-1023
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
Phenol Red Dextrose Agar is similar to Dextrose Agar (LC-1021) with the addition of phenol red as a pH indicator. It is recommended to determine the ability of various organisms to ferment dextrose. Being a solid medium, it has the advantage of allowing fermentation reactions under aerobic and anaerobic conditions.
Key features
Applications
Confirmation and differentiation of dextrose fermenters.
Industry
Food.
Preparation
40 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Peptone mixture provides nitrogen, vitamins, minerals and amino acids essential for growth, and allows the abundant growth of a wide variety of fastidious microorganisms. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Dextrose is the fermentable carbohydrate providing carbon and energy. Phenol red is the pH indicator. Bacteriological agar is the solidifying agent.
Phenol Red Dextrose Agar is an excellent substrate for streptococci, as well as for other less fastidious bacteria. A yellow color indicates fermentation, as the acid production reacts with the phenol red pH indicator. The formation of gas causes bubbles to appear at the base of the medium, which can lead to agar fragmentation. A control of Phenol Red Agar without carbohydrates should be used to control false positives.
Technical specifications
| Solubility | Slightly opalescent |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Pink |
| Color of the prepared medium | Red |
| Final pH (25 °C) | 7.4 ± 0.2 |
| Amount per litre | 40 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Dextrose | 10 |
| Bacteriological agar | 15 |
| Peptone mixture | 10 |
| Phenol red | 0.025 |
| Sodium chloride | 5 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 40 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.
Instructions for use
- Inoculate the medium by stabbing into the butt. If desired, inoculate obligate anaerobic bacteria into melted medium that has been cooled to 45 °C. Allow the agar to solidify prior to incubation.
- Incubate at 37 °C for 18-48 hours (or anaerobically for 24-72 hours).
- Examine periodically for growth, acid production and gas formation.
Quality control
Microbiological test
Incubation conditions: 37 ± 1 °C / 18-48 h.
| Microorganism | Characteristic reaction |
|---|---|
| Proteus vulgarisATCC 13315 | Acid (+) / Gas (+) |
| Salmonella typhimuriumATCC 14028 | Acid (+) / Gas (+) |
| Escherichia coliATCC 25922 | Acid (+) / Gas (+) |
| Alcaligenes faecalisATCC 8750 | Acid (-) / Gas (-) |
Bibliography
- Diagnostic Procedures and Reagents 3rd Edition p. 107. 1950.
- Association of Official Analytical Chemists. 1995 official methods of analysis of AOAC Arlington, VA.
- Baron EJ LR Peterson and S.M. Finegold 1994. Bailey & Scott's diagnostic microbiology, 9th edition. Mosby-Year Book, Inc. St. Louis, MO.
- Murray, PR., E.J. Baron M.A. Pfaller F.C. Tenover and R.H. Yolken (ed) 1995. Manual of clinical microbiology, 6th edition. American Society for Microbiology, Washington DC.
What you receive
The product
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