ANTIBIOTIC ASSAY MEDIUM NO. 9 (POLYMYXIN BASE AGAR (VEG.)

Description

Antibiotic Veg Assay Medium No.9 (Polymyxin Veg Base Agar) is prepared by incorporating vegetable peptones in place of animal peptones, making the medium BSE, TSE risks free. This can be used for the same purpose of Antibiotic Assay Medium No.9 (Polymyxin Base Agar) widely recommended for assay of Polymyxin B, Colistimethate sodium and Colistin using Bordetella bronchiseptica as test organism. Carbenicillin assay is also performed using this medium with Pseudomonas aeruginosa. The medium is numerically identical with the name assigned by Groove and Randall. Higher agar concentration provides control over the diffusion activity of polymixin B antibiotics and provides solid substratum to support the seed agar layer. 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 culture can be overlaid. Even distribution of the layer is important.