Extract Agar (FDA Agar)

Intended Use

Recommended for general cultivation of bacteria as well as routine testing of disinfectants and antiseptics.

Composition**

Final pH (at 25°C): 7.3±0.2

# Equivalent to Beef extract

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 35.0 grams in 1000 ml purified/distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 mins. Cool to 45-50°C. Mix well and pour into sterile Petri plates.

Principle And Interpretation

FDA Agar is used for general cultivation of bacteria as well as for routine testing of antiseptics and disinfectants. FDA Agar is also known as AATCC bacteriostasis agar where AATCC stands for American Association of Textile Chemists and Colourists (3). FDA agar is the formulation specified by Food and Drug Administration, U.S.A. and also by Association of Analytical Chemists (AOAC) (3,4). It is used for detecting antibacterial activity of fabrics. FDA agar is a relatively simple formulation. HM peptone B and Peptone provide the nutrients required for microbial growth. Sodium chloride maintains osmotic equilibrium.

Type of specimen

Disinfectant samples

Specimen Collection and Handling

For samples follow appropriate techniques for handling specimens as per established guidelines (1,2). 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. Further biochemical and serological tests must be carried out for complete identification of bacteria.

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 Off white to yellow coloured homogeneous free flowing powder

Gelling Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium Amber coloured clear to slightly opalescent gel forms in Petri plates.

Reaction Reaction of 3.5% w/v aqueous solution at 25°C. pH : 7.3±0.2

pH 7.10-7.50

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 (1,2).

Reference

1. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
2. 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.
3. Technical Manual of AATCC, Vol. 61, 1985-86, AATCC, Research Triangle Park, N.C.
4. Williams (Ed.), 1984, Official Methods of Analysis of the AOAC, 14th ed. AOAC, Washington, D.C.