Antibiotic Assay Medium C

Intended Use

Recommended for turbidimetric assay of a wide variety of antibiotics in accordance with BP.

Composition**

pH after sterilization: 7.0±0.1

**Formula adjusted, standardized to suit performance parameters

# Equivalent to Beef extract

Note: While assaying Josamycin & Josamycin propionate, adjust the pH to 8.0 ±0.1

Directions

Suspend 19.9 grams (the equivalent weight of dehydrated medium per litre) in 1000 ml R-water/ purified /distilled water. Heat with frequent agitation to dissolve the medium completely. Dispense into tubes or flasks as desired. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes or as per validated cycle. Adjust the pH of the medium, using freshly prepared buffer solution as recommended by the British pharmacopoeia for the antibiotic assayed.

Advice: Recommended for the microbiological assay of Colistimethate sodium, Dihydrostreptomycin sulphate, Erythromycin estolate, Erythromycin ethylsuccinate, Framycetin sulphate, Gentamicin sulphate, Gramicidin, Kanamycin acid sulphate, Kanamycin monosulphate, Neomycin sulphate, Rifamycin sodium, Spiramycin, Streptomycin sulphate, Tylosin, Tylosin tartarate, Tyrothricin and Vancomycin hydrochloride according to British Pharmacopoeia.

Principle And Interpretation

This medium is used in turbidimetic assay of several antibiotics. The composition of the medium is in accordance to the specifications detailed in the British Pharmacopoeia (1). Turbidimetric methods for determining the potency of antibiotics are inherently more accurate and more precise than comparable agar diffusion procedures (5)

Peptone, HM peptone B and yeast extract provide essential nutrients and growth factors for enhanced microbial growth. Sodium chloride maintains the osmotic equilibrium while phosphates are incorporated in the medium to provide good buffering action. Glucose monohydrate serves as the carbon and energy source for faster growth.

Turbidimetric antibiotic assay is based on the change or inhibition of growth of a test microorganims in a liquid medium containing a uniform concentration of an antibiotic (2). Use of this method is appropriate only when test samples are clear.

Type of specimen

Pharmaceutical sample

Specimen Collection and Handling

For pharmaceutical sample samples follow appropriate techniques for handling specimens as per established guidelines (1). 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

• Freshly prepared medium plates must be used or it may result in erroneous results.
• Use of this method is appropriate only when test samples are clear.

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 coloured homogeneous free flowing powder

Colour and Clarity of prepared medium: Light yellow coloured clear solution without any precipitate

pH: 6.90-7.10

Cultural Response

Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours. (Key: 1.* - While assaying Josamycin and Josamycin propionate adjust the pH of the medium to 8.0 ± 0.1 2.# - While assaying Vancomycin hydrochloride, the incubation temperature is maintained at 37-39°C)

Key: (*) Corresponding WDCM numbers.

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and use freshly prepared medium. 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 (3,4).

Reference

1. British Pharmacopoeia, 2016, TheStatinery Office, British Pharmacopoeia
2. Chapin-Robertson and Edberg, 1991, Measurement of Antibiotics in Human Body fluids:Techniques and significance. Antibiotics in Laboratory medicine, New York pp 305
3. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
4. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual Clinical Microbiology, 11th Edition. Vol. 1.
5. Rippere RA. Some principles of microbiological turbidimetric assays of antibiotics. J Assoc Off Anal Chem. 1979 62(4):951-6.