(PERICOLOSO)
The Clinical and Laboratory Standards Institute (CLSI) document M22-A3, "Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard — Third Edition," is a cornerstone reference for clinical microbiology laboratories performing disk diffusion antimicrobial susceptibility testing (AST). This essay explains the document’s purpose and key content, its impact on laboratory practice and patient care, and how clinicians and laboratorians can responsibly access and use the standard (including locating the PDF through legitimate channels).
: These consensus-based resources are widely recognized for improving the quality and efficiency of medical laboratory testing worldwide. Clinical & Laboratory Standards Institute | CLSI clsi m22a3 pdf link
The document addresses several core components of laboratory quality assurance: Essay: CLSI M22-A3 — Significance, Contents, and Access
The primary objective of the M22-A3 guideline is to define the responsibilities of both the manufacturer and the end-user laboratory regarding the quality control (QC) of microbiological media. Historically, laboratories were often required to perform extensive "in-house" testing on every batch of commercially prepared media to ensure sterility and growth support. However, M22-A3 identifies specific media with a high history of stability and consistent performance, classifying them as "exempt" from routine user QC testing, provided the manufacturer is compliant with stringent quality standards. This classification allows laboratories to trust the manufacturer’s Certificate of Analysis (CoA) for low-risk media, such as Blood Agar or MacConkey Agar, thereby reducing the consumption of reagents, personnel time, and financial resources. Clinical and Laboratory Standards Institute