Effects of paper on performance of antibiotic-impregnated disks.

Grades of paper used in the manufacture and assay of antibiotic susceptibility disks have significant effects on the diffusion of antibiotics from the paper when compared to a control grade of paper. The papers also evoke different microbiological responses to changing concentrations of some antibiotics. Regulatory implications and the need for further standardization of assays among control laboratories are explored. Grades of paper generally used for assay and control of susceptibility disks, on the other hand, appear to be comparable to each other in both respects.