Each section/table gives recommendations for antimicrobial agents to test, MIC interpretive criteria, and disk diffusion zone diameter breakpoints. Updated Taxonomy:
Common causes of bacterial gastroenteritis requiring specific microaerophilic conditions.
Standardizing AST for these rare bugs is a growing challenge. Studies show that using "non-standardized" methods (anything not specified in M45) can lead to inconsistent results, which is a major hurdle in combating antimicrobial resistance .
While the heavy-hitting M100 focuses on common aerobic and anaerobic bacteria, CLSI M45 provides standardized methods for antimicrobial susceptibility testing (AST) of pathogens that occur less frequently or have complex growth requirements. clsi document m45 pdf
Your Comprehensive Guide to CLSI Document M45: Understanding Infrequently Encountered Bacteria
This is a quantitative method used to determine the minimal inhibitory concentration (MIC) of an antibiotic. A standardized suspension of the bacterium is inoculated into a series of broth wells containing different concentrations of an antimicrobial agent. After incubation, the lowest concentration that prevents visible bacterial growth is the MIC, which helps determine if the organism is susceptible, intermediate, or resistant to that drug. The document provides detailed instructions for preparing the testing panels, inoculum, and incubation conditions.
The field of microbiology and AST is not static. CLSI has been actively working on a . Documentation from CLSI meetings indicates that as of 2023, a revision process was underway, with a target publication date of 2025 for the new edition. This future edition is expected to incorporate further taxonomic updates, new antimicrobial agents, and potentially new recommendations for a wider range of organisms. It will also need to align with evolving FDA regulations and other global standards. A standardized suspension of the bacterium is inoculated
Some infrequent organisms possess intrinsic resistance traits. M45 outlines these traits so laboratories do not report drugs that are clinically ineffective, even if they appear active in vitro . Standardizing Global Data
The CLSI M45 document, titled "Guidelines for Antimicrobial Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria," is a peer-reviewed standard developed by global experts. It provides clinical laboratories with specific phenotypic methodologies, quality control (QC) criteria, and interpretive breakpoints for organisms that are either rarely encountered or difficult to grow using standard laboratory media.
The 2016 third edition was a substantial update. It introduced and included several new tables to address organisms that were becoming more easily identifiable by advanced methods like sequencing or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The intent was to help laboratories determine an approach for testing these diverse organisms that is relevant to their specific practice settings and available technologies. Notably, the third edition is available as an electronic PDF only , comprising 120 pages. quality control (QC) criteria
Formally known as nutritionally variant streptococci.
The document has undergone several revisions:
As a copyrighted standard, the CLSI M45 document is not freely and legally available for download from public websites. The legitimate ways to obtain the PDF are as follows: