NIH Agar

Intended Use

Recommended for sterility testing and for cultivation and maintenance of isolates from sterility testing of biological products.

Composition**

Final pH ( at 25°C) 7.1±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 43.05 grams in 1000 ml purified/distilled water. Heat to boiling to dissolve the medium completely. Dispense into test tubes or flasks as desired. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. As per USP, it is recommended to add 0.05% sodium thioglycollate or 0.03% Thioglycollic acid for neutralization of bacteriostatic effect of mercuric compounds.

Principle And Interpretation

NIH Agar is formulated according to the agar medium specified by USPHS sterility test (7). This medium can be used for sterility testing and also for cultivating the isolates from biological products tested for sterility. This medium is also recommended by the National Institute of Health (NIH) for sterility testing of turbid appearing biological products (3). NIH Medium has a similar composition as Fluid Thioglycollate Medium, except sodium thioglycollate and resazurin. Also the agar concentration is more in NIH Medium than in Fluid Thioglycollate Medium.

NIH medium is a nutritious medium containing nutrients like Tryptone, yeast extract and the amino acid L-cystine. It contains the fermentable carbohydrate dextrose and sodium chloride for maintaining osmotic equilibrium. NIH Medium is devoid of sodium thioglycollate. U.S. Pharmacopoeia (6) has recommended using this medium with sodium thioglycollate (0.05%) or thioglycollic acid (0.03%) for the sterility testing of biological products containing mercurial preservatives, since sodium thioglycollate neutralizes the bacteriostatic effect of mercuric compounds (4, 5).

Type of specimen

Pharmaceutical samples for sterility testing

Specimen Collection and Handling

For pharmaceutical samples, follow appropriate techniques for sample collection, processing as per guidelines (3,6,7). 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 clinical 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.

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: Cream to yellow homogeneous free flowing powder

Gelling: Firm, comparable with 1.5% Agar gel

Colour & Clarity of prepared medium: Light amber coloured clear to slightly opalescent gel forms in Petri plates

Reaction: Reaction of 4.3% w/v aqueous solution at 25°C. pH : 7.1±0.2

pH: 6.90-7.30

Cultural Response:

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

Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours with addition of sodium thioglycollate.

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. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore.
4. Nungester, Hood and Warren, 1943, Proc. Soc. Exp. Biol. Med. 52 : 287
5. Portwood, 1944, J. Bacteriol., 48 : 255.
6. The United States Pharmacopoeia, 2006, USP29/NF24. The United States Pharmacopoeial Convention, Rockville, MD.
7. USPHS Reg., 73, 730: Federal Register, 1970, Vol. 35, No. 0171, p. 13:930.