A critical foodborne pathogen capable of causing severe meningitis and septicemia in newborns, pregnant women, and immunocompromised patients.
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.
Many institutional, hospital, and university libraries maintain an active CLSI eClip subscription, giving laboratory staff instant digital access to the entire portfolio of documents, including M45 and M100.
CLSI M45 is an indispensable companion to routine susceptibility testing. It offers a standardized safety net for challenging organisms that commercial panels ignore. While not every lab will run M45 daily, every clinical microbiology lab should have access to it – either internally or via a reference lab – and understand its principles to ensure appropriate antibiotic therapy for patients with uncommon or fastidious infections.
Provides expert-vetted minimum inhibitory concentration (MIC) breakpoints where clinical data is sparse. clsi document m45 pdf
The document includes detailed testing methods for several groups of challenging pathogens, including but not limited to:
Comprehensive Guide to CLSI Document M45: Laboratory Testing for Infrequently Isolated or Fastidious Bacteria
Mueller-Hinton broth supplemented with 2% to 5% lysed horse blood for fastidious organisms.
Because many of these organisms grow slowly, preparing a direct colony suspension equivalent to a 0.5 McFarland standard is crucial. Incubation environments vary by organism, ranging from ambient air to 5%–10% CO₂, with incubation times extending from 24 up to 48 hours for exceptionally slow growers. Interpreting Results: The Role of "No Breakpoint" A critical foodborne pathogen capable of causing severe
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Formerly known as nutritionally variant streptococci, frequently implicated in endocarditis.
| Edition | Year | Key Changes | |---------|------|--------------| | M45-A | 2005 | First edition; introduced methods for 22 organism groups. | | M45-A2 | 2010 | Added breakpoints for Burkholderia cepacia , Stenotrophomonas maltophilia . | | M45-A3 | 2015 | Expanded to include Aeromonas , Vibrio , and Plesiomonas . Updated QC strains. | | | 2020+ | Current edition. Includes new breakpoints for Campylobacter , revised Haemophilus testing, and quality control updates. |
Use this document when an organism is identified, but susceptibility cannot be reliably predicted, and standard M100 methods do not apply. Exclusions: Documentation from CLSI meetings indicates that as of
CLSI Document M45 (3rd Edition) provides standardized methods for antimicrobial dilution and disk susceptibility testing of infrequent or fastidious bacteria, covering organisms like Abiotrophia , Vibrio spp., and bioterrorism agents. It establishes essential breakpoints and QC ranges, offering detailed technical procedures for broth microdilution and agar disk diffusion to ensure accurate lab results. For the complete document guidelines, visit CLSI Webstore . preview_CLSI+M45-Ed3.pdf - ANSI Webstore
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The third edition is a 120-page document with an ISBN of for the PDF version. It includes important taxonomic updates and new tables to address organisms that are more likely to be identified using modern techniques like sequencing or MALDI-TOF mass spectrometry. This edition is recognized by the U.S. Food and Drug Administration (FDA) as a consensus standard for use in satisfying regulatory requirements.
What do you intend to use (e.g., Etest/gradient strips, broth microdilution, or disk diffusion)?