Penicillin

Publisher Website
Google Scholar
Abstract
Procedures are given for assaying penicillin by the cylinder plate and the serial dilution methods. Factors which affect the cylinder-plate method are discussed. The influence of the following factors is considered: depth of agar, stock culture of the test organism, pH of the medium, the relationship between the rate of diffusion of penicillin and growth of the test organism, conc. of the inoculum, and condition of the ground glass surface of the cylinder. Under conditions described, it takes approx. 0.045 Oxford unit per ml. of broth to inhibit growth of the test organism at 18 hrs. and 0.1 unit per ml. of broth at 40 hrs.