This medium is commonly used for assaying Streptomycin by cylinder plate method using Bacillus subtilis as test organism. This method is used in the assay of commercial preparations of antibiotics, as well as for antibiotics in body fluids, feeds etc.Medium composition is in accordance to the specifications detailed in the FDA (1) and numerically identical to the name assigned by Grove and Randall (2).
Peptic digest of animal tissue, yeast and beef extract provides necessary growth nutrients for the test organisms like Bacillus subtilis.
The medium provides solidified substratum for growth of organims. The pH-7.9 maintained in this medium- provides optimum growth conditions for Bacillus subtilis (3). This medium is used to prepare the base as well as seed layer in the microbiological assay of antibiotics such as Dihydrostreptomycin, Framycetin and Kanamycin B.
To perform the antibiotic assay the Base Agar should be prepared on the same day as the test. For the cylinder method, a base layer of 21 ml is required. Once the base medium has solidified, seed layer inoculated with the standardized test culture can be overlaid. Even distribution of the layer is important.
Storage and Shelf-life:
Store below 30°C in tightly closed container and use freshly prepared medium. Use before expiry date on the label.
References:
1. Tests and Methods of Assay of Antibiotics and Antibiotic containing Drugs, FDA, CFR, 1983 Title 21, Part 436, Subpart D, Washington, D.C.: U.S. Government Printing Office, paragraphs 436, 100-436, 106, p. 242-259, (April1).
2. Grove and Randall, 1955, Assay Methods of Antibiotics Medical Encyclopedia, Inc. New York.
3. Stearn and Stearn, J Bacteriol. 1933. 26(1): 37-55.