About CLSI Antimicrobial and Antifungal Susceptibility Testing Resources

CLSI develops standardized reference methods that measure the susceptibility of bacteria and fungi to antimicrobial agents in vitro. Susceptibility testing breakpoints, interpretive categories, and QC parameters are established by the Subcommittee on Antimicrobial Susceptibility Testing (AST) after comprehensive review of all available relevant data.

In this regard, the CLSI Subcommittee on AST is responsible for developing and updating the following susceptibility testing documents:

M02—Performance Standards for Antimicrobial Disk Susceptibility Tests
M07—Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically
M11—Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria
M45—Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria
M100—Performance Standards for Antimicrobial Susceptibility Testing

The Subcommittee on Antifungal Susceptibility Tests is responsible for developing and updating the following susceptibility testing documents:

M27—Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts and corresponding supplement M27S
M38—Reference Method for Broth Dilution Antifungal Susceptibility Testing of Filamentous Fungi
M44—Method for Antifungal Disk Diffusion Susceptibility Testing of Yeasts and corresponding supplement M44S
M51—Method for Antifungal Disk Diffusion Susceptibility Testing of Nondermatophyte Filamentous Fungi and corresponding supplement M51S

The details of the data necessary to establish breakpoints, QC parameters, and how the data are presented for evaluation are described in CLSI document M23.

M23 is an important foundation guideline that supports these susceptibility testing standards. The purpose of M23 is to provide guidance on the data submitted by sponsors and the procedures followed by the CLSI Subcommittee on AST to establish or revise QC ranges and susceptibility testing breakpoints for inclusion in CLSI documents. The process for determination of breakpoints and QC ranges for antifungal agents is broadly the same as for the antibacterial agents, and the principles described in M23 also apply to antifungal agents.

Subcommittee on Antimicrobial Susceptibility Testing Mission Statement

The Subcommittee on Antimicrobial Susceptibility Testing is composed of representatives from the professions, government, and industry, including microbiology laboratories, government agencies, health care providers and educators, and pharmaceutical and diagnostic microbiology industries. Using the CLSI voluntary consensus process, the subcommittee develops standards that promote accurate antimicrobial susceptibility testing and appropriate reporting.

The mission of the Subcommittee on Antimicrobial Susceptibility Testing is to:
• Develop standard reference methods for antimicrobial susceptibility tests.
• Provide quality control parameters for standard test methods.
• Establish breakpoints for the results of standard antimicrobial susceptibility tests.
• Provide suggestions for testing and reporting strategies that are clinically relevant and cost effective.
• Continually refine standards and optimize detection of emerging resistance mechanisms through development of new or revised methods, breakpoints, and quality control parameters.
• Educate users through multimedia communication of standards and guidelines.
• Foster a dialogue with users of these methods and those who apply them.

The ultimate purpose of the subcommittee’s mission is to provide useful information to enable laboratories to assist the clinician in selecting appropriate antimicrobial therapy for patient care. The standards and guidelines are meant to be comprehensive and to include all antimicrobial agents for which the data meet established CLSI guidelines. The values that guide this mission are quality, accuracy, fairness, timeliness, teamwork, consensus, and trust.