scope:

This document describes the standard agar disk diffusion techniques used to determine the in vitro susceptibility of bacteria that grow aerobically. It addresses preparation of agar plates, testing conditions (including inoculum preparation and standardization, incubation time, and incubation temperature), interpretation of results, QC procedures, and limitations of disk diffusion methods. To assist the clinical laboratory, suggestions are provided on the selection of antimicrobial agents for routine testing and reporting.

Standards for testing the in vitro susceptibility of bacteria that grow aerobically using dilution methods are found in CLSI document M07³; standards for testing the in vitro susceptibility of bacteria that grow anaerobically are found in CLSI document M11.⁴ Guidelines for standardized susceptibility testing of infrequently isolated or fastidious bacteria that are not included in CLSI documents M02, M07,³ or M114 are available in CLSI document M45.⁵

The susceptibility testing methods provided in this standard can be used in laboratories around the world including, but not limited to:

• Medical laboratories

• Public health laboratories

• Research laboratories

• Food laboratories

• Environmental laboratories