High grade Antibiotic Assay Medium No. 9 (Polymyxin Base Agar) is supplied by Micromaster. It is available in the form of a cream to yellow homogeneous free flowing powder which has a pH in the range of 7 to 7.4. Casein enzymic hydrolysate and papaic digest of soyabean meal serves as source for essential nutrients. Dextrose stimulates the growth by providing carbon and energy. Phosphates in the medium enhances buffering action and sodium chloride maintains osmotic equilibrium in the medium. Agar concentration provides control over the diffusion activity of polymixin B antibiotics and provides solid substratum to support the seed agar layer.This product should be stored between 30C in a tightly closed container. Store in dry ventilated area protected from extremes of temperature and sources of ignition.

Quantity provided: 500 g/pack

This medium is widely recommended for assay of Polymyxin B, Colistimethate sodium and Colistin using Bordetella bronchiseptica as test organisms. Carbenicillin assay is also performed using this medium with Pseudomonas aeruginosa. The medium is numerically identical with the name assigned by Groove and Randall. 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.