Ammonium Phosphate Agar

Intended Use

Recommended for detecting the ability of microorganisms to utilize ammonium phosphate as a source of nitrogen.

Composition**

Final pH ( at 25°C): 7.0±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 26.45 grams in 1000 ml purified / distilled water. Mix thoroughly and heat to boiling to dissolve the medium completely. Dispense in tubes and sterilize by autoclaving at 118-121°C (12-15 lbs pressure) for 10 minutes. Cool to 45-50°C. Allow the tubes to cool in slanted position.

Principle And Interpretation

Staphylococci are generally found on the skin and mucous membranes of humans and other animals. Micrococci are found in the environment and as transient members of the microflora on the skin of humans and other mammals (4). Ammonium Phosphate Agar was formulated by Hucher (1) for detecting microorganisms that can utilize ammonium phosphate as a source of nitrogen. This medium is particularly useful during the differentiation of Micrococci from Staphylococci. Dextrose upon fermentation produces acid, which is indicated by the colour change of the bromocresol purple indicator to yellow. Free living, non pathogenic, saprophytic or facultatively parasitic Micrococci utilize dextrose and ammonium phosphate present in the medium. Potassium chloride and magnesium sulphate provide necessary salts for the growth of microorganisms.

Type of specimen

Environmental samples

Specimen Collection and Handling

For samples follow appropriate techniques for handling specimens as per established guidelines (2,3). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/ face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. This medium is general purpose medium and may not support the growth of fastidious organisms.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

Quality Control

Appearance: Light yellow to light purple homogeneous free flowing powder

Gelling: Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium: Purple coloured clear to slightly opalescent gel forms in tubes as slants

Reaction: Reaction of 2.65% w/v aqueous solution at 25°C. pH : 7.0±0.2

pH: 6.80-7.20

Cultural Response: Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours.

Key : (*) Corresponding WDCM numbers.

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and the prepared medium at 20-30°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition. Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (2,3).

Reference

1. Hucher, 1924, New York State Exp. Sta. Tech. Bull., 100:36.
2. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
3. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.
4. Koneman E. W., Allen S. D., Janda M. W., Schreckenberger C. P., WinnC. W., (Eds), Colour Atlas and Textbook of Diagnostic Microbiology,4th E d, J. B. Lippincott Company.