: This guideline does not address commercial susceptibility testing systems; it focuses on reference methodologies.
For clinical microbiology labs, relying on standard AST methods (like those in M100) for fastidious organisms can lead to erroneous results. The CLSI M45-A3 standard provides the necessary standardization to ensure accurate, reproducible, and clinically relevant susceptibility data.
As with many scientific standards, the M45 document is subject to periodic corrections to ensure accuracy. A significant correction notice was issued by CLSI on for the third edition, primarily concerning the ATCC® number for the quality control strain Pseudomonas aeruginosa . The notice corrects several instances throughout the document where the number ATCC 27583 was listed, changing it to the correct ATCC 27853 . This correction appears in tables related to Aeromonas spp., Vibrio spp., and various QC ranges. Anyone referencing a copy of M45 should ensure they are using a version that incorporates these corrections or consult the official notice to verify the correct QC strains.
Brief guidance on the clinical relevance of specific resistance mechanisms. Why Is the M45 Document Critical for Patient Care? clsi document m45 pdf
Halophilic organisms requiring specific salt concentrations for optimal growth and testing. Testing Methodologies Recommended in M45
You can purchase the electronic PDF or a printed copy directly from the CLSI online shop.
Align your internal Standard Operating Procedures (SOPs) with the specific incubation times, temperatures, and media types outlined in the latest M45 edition. : This guideline does not address commercial susceptibility
For many organisms, clinical break-points do not exist. M45 utilizes Epidemiological Cutoff Values (ECVs) to distinguish wild-type (WT) populations from those with acquired resistance mechanisms.
Each section/table gives recommendations for antimicrobial agents to test, MIC interpretive criteria, and disk diffusion zone diameter breakpoints. Updated Taxonomy:
Provides approved, standardized methodologies for testing slow-growing or nutrient-fastidious organisms. As with many scientific standards, the M45 document
Implementing the guidelines found in the CLSI M45 PDF requires precise attention to pre-analytical and analytical variables. Media Selection
While M100 covers common pathogens like E. coli or S. aureus , M45 focuses on the "difficult" ones—organisms that are either rarely isolated or have very specific, "fastidious" growth requirements. Without standardized guidance, labs might struggle to provide accurate susceptibility results, which are vital for clinicians treating rare but serious infections. What’s Inside the Latest Edition?