A brief history of the antibiotic assay

The quantitative use of zones of agar made inhibitory to the growth of one microorganisms by diffusing substances produced by another organism was in use at least as early as 1885 (Analytical Microbiology, Kavanagh, 1963). The first official assays of penicillin were carried out in 1943. Publication of the theoretical aspects involved was published by Cooper and Woodman in 1946 in Pathological Bacteriology. The antibiotic assay used by pharmaceutical companies is primarily the agar plate diffusion assay. Some products that are a mixture of polymers may have a specific monograph stating that they must be assayed by a turbidimetric method. Such an example is Gramicidin. Continue reading →