Specialty Areas

Antimicrobial Susceptibility Testing (AST)

Setting the Standard

Advancing the Field of Microbiology with Timely AST Standards

CLSI is uniquely qualified to serve as the go-to source for AST methods and interpretive criteria. Through the implementation of a well-defined, robust standards development program and participation of renowned experts, and by upholding demonstrable practices and principles, CLSI provides world class guidance in antimicrobial susceptibility testing that can be used with confidence to identify and update susceptibility test interpretive criteria.

CLSI AST standards are developed through the work of several commitees and working groups, staffed by subject matter experts from around the world. These teams convene twice annually during our Global Committees Week sessions.

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Expertise

Recognized Authority for Microbiology and AST

CLSI was first accredited by ANSI in 1978 and is the sole nationally or internationally accredited SDO developing and revising AST interpretive criteria worldwide. CLSI is also globally recognized for its administration of the International Organization for Standardization (ISO) Technical Committee on Clinical Laboratory Testing and In Vitro Diagnostic Test Systems (ISO TC 212). As the secretariat for ISO TC 212/WG 4, CLSI is actively involved in ensuring global harmonization across standardization efforts.

Subcommittees are responsible for developing CLSI AST guidance. These groups write draft documents, evaluate and respond to comments on content throughout the document development process, conduct scheduled document reviews, and are responsible for continual revision of certain documents. CLSI is accredited by the American National Standards Institute (ANSI) and these committees operate in compliance with applicable ANSI requirements.

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CLSI has Established AST Subcommittees in the Following Areas:

Antimicrobial Susceptibility Testing (AST) Subcommittee

The AST Subcommittee provides useful information to laboratories, enabling them to advise clinicians in the selection of appropriate antimicrobial therapy in response to bacteria. This subcommittee operates through a network of AST Working Groups.

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Subcommittee on Antifungal Susceptibility Tests (AFUNG)

The Subcommittee on Antifungal Susceptibility Tests (AFUNG) collaborates to develop standards and guidelines that promote accurate antifungal susceptibility testing and appropriate reporting. This subcommittee operates through a number of Antifungal Working Groups.

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Veterinary Antimicrobial Susceptibility Testing (VAST)

The VAST Subcommittee collaborates to develop and promote performance standards, breakpoints, and interpretive categories for in vitro antimicrobial susceptibility testing of bacteria isolated from animals. The VAST Subcommittee operates through a number of AST & VAST Working Groups.

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AST Products

Performance Standards for Antimicrobial and Antifungal Susceptibility Testing

The subcommittee reviews data from various sources and studies (eg, in vitro, pharmacokinetic-pharmacodynamic, and clinical studies) to establish antimicrobial susceptibility test methods, breakpoints, and quality control ranges. This guidance is presented in an array of standards documents and supporting tools.

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AST News Updates

AST Meeting Files

AST Rationale Documents

Breakpoint Implementation Tools

CLSI M100-AST Updates Webinar

AST Educational Webinars and Programs

Other AST Resources

CLSI MicroFree™

Ensuring Global Access to CLSI Breakpoints

CLSI MicroFree™ enables free access to the most trusted and information on Antimicrobial Susceptibility Testing as a public health service to ensure labs and clinicians everywhere can participate in the efforts to combat antimicrobial resistance (AMR).

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Latest AST Insights

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Antimicrobial Susceptibility Testing

Standards in motion: Highlights from June 2025 Committees Week

CLSI recently hosted it's June 2025 Committees Week in Frisco, Texas. Here are key highlights from the meetings.

Antimicrobial Susceptibility Testing

Top Reasons to Attend the CLSI AST Committees Week Meeting

CLSI is hosting the annual AST Committees Week Meeting May 31-June 3rd. This event is vital to the continued collaboration of laboratory professionals dedicated to quality patient care and pushing AST standards forward.

Antimicrobial Susceptibility Testing

A Week for Collaboration and Consensus: CLSI’s January 2024 Meetings

CLSI’s Committees Weeks are an opportunity for the CLSI expert community to meet and connect with colleagues for a week of information sharing, consensus building, networking, and camaraderie. Committees Weeks are where the hard work behind CLSI’s standards and guidelines takes place—committees and subcommittees, following CLSI’s voluntary consensus process, work together on new and revised CLSI standards in development.

Register for AST News Updates

The CLSI Outreach Working Group (ORWG) works to efficiently convey information regarding contemporary AST practices, recommendations, and resources to the clinical microbiology community. This biannual CLSI AST News Update highlights current issues related to antimicrobial susceptibility testing (AST) and reporting.

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Share Your Expertise

Join our community of industry leaders who volunteer their experience and knowledge to drive innovation and excellence in laboratory practices.

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AST Projects in Progress

Please note, the publication dates are subject to change based on document development activities.

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