ABSTRACT
The earliest methods for assessing the effects of antibiotics on bacteria involved the use of ditches cut into agar plates. Antibiotic solution poured into the ditch was allowed to diffuse out to inhibit the growth of the bacteria streaked perpendicular to the ditch. In 1943, Foster and Woodruff used paper strips impregnated with antibiotics as an alternative source of diffusion [1]. The agar diffusion principles used in the bioassay of penicillin G in plasma were further used to develop the disk diffusion test [2]. Antibiotic reservoirs that initially consisted of antibiotic solutions in agar wells or cylinders were soon replaced by paper disks impregnated with antibiotics.
