This is the gold standard for most fastidious organisms. The document defines the specific supplementation needed for the broth, the exact inoculum size, and specialized incubation times (often 24 to 48 hours). Agar Dilution
A foodborne pathogen capable of causing severe meningitis and septicemia in newborns and elderly populations.
Which are you trying to test?
Using standard AST methods on fastidious or rare organisms can lead to inaccurate results. This can cause inappropriate patient treatment or unrecognized antibiotic resistance. Key Benefits of Implementing CLSI M45:
The CLSI M45 document is a comprehensive guideline that fills a unique niche in the world of antimicrobial susceptibility testing (AST). While CLSI's primary documents (such as M07 and M100) provide methods for testing common, rapidly growing aerobic bacteria, M45 is designed for the outliers. These are the bacteria that are in a standard clinical laboratory or are fastidious , meaning they have complex nutritional requirements and are difficult to grow and maintain in a culture medium. clsi document m45 pdf
The document includes detailed testing methods for several groups of challenging pathogens, including but not limited to:
Available as an electronic PDF download, a hardcopy print, or through an online subscription service (eCLIPSE).
Includes Haemophilus (non-influenzae), Aggregatibacter , Cardiobacterium , Eikenella , and Kingella , which are notorious causes of culture-negative endocarditis. Key Content Structure of the PDF
CLSI actively pursues copyright infringement. For accredited labs, using an illegitimate PDF during an inspection can result in citations. This is the gold standard for most fastidious organisms
If you want, I can:
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.
Antimicrobial breakpoints change. They are updated based on emerging resistance mechanisms and pharmacokinetic/pharmacodynamic (PK/PD) data. An old, free PDF from 2010 may list breakpoints for ciprofloxacin that are now considered dangerously high, leading to false-susceptible (very major) errors.
The primary goal of CLSI M45 is to provide essential guidance for antimicrobial susceptibility testing (AST) when resistance is a concern and the organism's susceptibility cannot be predicted by its identity alone. Which are you trying to test
Disclaimer: CLSI guidelines are copyrighted and regularly updated. Always refer to the most recent edition of CLSI M45 published by the Clinical and Laboratory Standards Institute. This article is for informational purposes and does not replace professional medical or laboratory advice.
Clinical laboratories face unique challenges when implementing CLSI M45 guidelines:
to perform susceptibility testing for diverse organisms relevant to their specific practice settings. Clinical & Laboratory Standards Institute | CLSI Accessing the PDF
Unlike the more common CLSI M100 document, which covers mainstream pathogens, M45 focuses exclusively on organisms that lack standardized testing criteria in standard manuals. It provides customized testing methodologies, incubation conditions, and interpretive breakpoints for specific bacterial groups. Why is CLSI M45 Essential for Laboratories?