scope:

This document describes the standard broth (macrodilution and microdilution) and agar dilution methods used to determine the in vitro susceptibility of bacteria that grow aerobically. It addresses preparation of broth and agar dilution tests, testing conditions (including inoculum preparation and standardization, incubation time, and incubation temperature), reporting of minimal inhibitory concentration (MIC) results, QC procedures, and limitations of the dilution test 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 the antimicrobial disk susceptibility testing method are found in CLSI document M02⁴; standards for testing the in vitro susceptibility of bacteria that grow anaerobically are found in CLSI document M11.⁵ Guidelines for standardized susceptibility testing of infrequently isolated or fastidious bacteria that are not included in CLSI documents M02,⁴ M07, or M11⁵ are available in CLSI document M45.⁶

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