Studies on Polymyxin: An Agar Diffusion Method of Assay

作者：Philip G. Stansly, M. E. Schlosser · 发表于：Journal of Bacteriology · 年份：1947 · DOI：10.1128/jb.54.5.585-597.1947 · 被引用次数：35 · 研究领域：Historical Medical Research and Treatments、Biosimilars and Bioanalytical Methods、Antibiotic Resistance in Bacteria

BaciUus polymyxa was originally detected as a producer of an antibiotic (Stansly, Shepherd, and White, 1947) by the fact that surrounding the colony of the organism was a clear zone of agar, whereas the remainder of the agar plate was covered with a layer of growth of the test organism. Obviously the anti-biotic diffused through the agar and prevented growth of the test organism up to a point where its concentration fell to a value below that required for this inhibition. It was, therefore, anticipated that it might be possible to de-velop an agar diffusion method to assay for potency similar to the well-known methods for penicillin (Abraham et al., 1941). It was soon apparent, however, that the methods used for the assay of peni-cillin were not strictly applicable to the assay of polymyxin. For example, in a preliminary experiment using ifiter paper disks saturated with solutions of polymyxin, insignificant zones of inhibition were obtained using Escherichia coli as the test organism, even with high concentrations of the antibiotic. Incuba-tion of the plates was at 37 C. Experiments were then undertaken, many of