scope:

This standard describes the reference agar disk diffusion method used to determine the in vitro antimicrobial susceptibility of bacteria that grow aerobically and includes:

• Agar plate preparation

• Testing conditions, including inoculum preparation and standardization, incubation time, and incubation temperature

• Results interpretation

• QC procedures

• Disk diffusion method limitations

To assist the medical laboratory, suggestions are provided for selecting antimicrobial agents for routine testing and reporting

Standards for testing the in vitro antimicrobial susceptibility of bacteria that grow aerobically using dilution methods are found in CLSI document M07.³ Standards for testing the in vitro antimicrobial susceptibility of bacteria that grow anaerobically are found in CLSI document M11.⁶ Guidelines for standardized antimicrobial susceptibility testing (AST) of infrequently isolated or fastidious bacteria that are not included in CLSI documents M02, M07,³ or M11⁶ are available in CLSI document M45.⁷ The AST 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