Cylinder-plate assays are used to determine the influence of an antibiotic on the growth rate of a target microorganism in a specific medium. Growth of the microorganism is inhibited around the cylinders depending on the potency of the antibiotic.
The following image shows the potency estimation of a Test sample in a cylinder-plate assay as recommended by U.S. Pharmacopeia <81>: Every plate contains six cylinders with three replicates of the Reference step (S3) and alternating one of the four concentration steps from the Standard (S1, S2, S4, S5), or the Test sample (U3). To account for inter-plate variation, a correction method is applied to the response data.