This method is based on the principle that the zone of growth inhibition around an antimicrobial-containing disk is inversely proportional to the MIC of the antimicrobial agent. Up to 12 disks can be placed on a 15-cm diameter Petri dish containing Mueller-Hinton agar seeded with a test organism. Zones of inhibition are recorded after overnight incubation at 35 °C. The degree of microbial growth inhibition is categorized as susceptible, intermediate (moderately susceptible), or resistant on the basis of the diameter of the zone of inhibition around each disk. The disk-diffusion method usually used is the Kirby-Bauer procedure, which is limited by the range of drugs and organisms that can be tested, but is well standardized (National Co.mMtieeJoLCJinica.l La.b.0.r§toIy...,Sí§.Q.d.aId.s 1995). Anaerobes should not be tested by disk diffusion.
Was this article helpful?