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Influence of clinical breakpoint changes from CLSI 2009 to EUCAST 2011 antimicrobial susceptibility testing

Michael Hombach1, Aline Wolfensberger, Stefan P Kuster

  • 1Institut für Medizinische Mikrobiologie, Universität Zürich, Zürich, Switzerland. mhombach@imm.uzh.ch

Journal of Clinical Microbiology
|April 19, 2013
PubMed

Insights

New antibiotic susceptibility testing guidelines significantly increased multidrug resistance rates in common Gram-negative bacteria. These changes highlight the need to re-evaluate resistance thresholds for accurate clinical decisions.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Clinical Pharmacy

Background:

  • Gram-negative rods are a significant cause of hospital-acquired infections.
  • Accurate antibiotic susceptibility testing is crucial for effective treatment.
  • Evolving resistance patterns necessitate updated testing guidelines.

Purpose of the Study:

  • To compare multidrug resistance (MDR) rates in Gram-negative bacteria using CLSI 2009 and EUCAST 2011 guidelines.
  • To identify specific bacterial species affected by guideline changes.
  • To determine the impact of breakpoint alterations on MDR classification.

Main Methods:

  • Retrospective analysis of antibiotic susceptibility testing data.
  • Comparison of MDR rates based on CLSI 2009 and EUCAST 2011 criteria.
  • Categorization of MDR isolates based on breakpoint changes.

Main Results:

  • EUCAST 2011 guidelines resulted in increased MDR rates for Klebsiella pneumoniae (2.2%), Enterobacter cloacae (1.1%), Pseudomonas aeruginosa (0.7%), and Escherichia coli (0.4%).
  • Breakpoint changes accounted for 24% of MDR Enterobacteriaceae and 12% of MDR P. aeruginosa isolates.
  • The updated EUCAST guidelines identified a higher prevalence of multidrug resistance.

Conclusions:

  • The EUCAST 2011 guidelines lead to a higher reported MDR rate compared to CLSI 2009.
  • Breakpoint revisions significantly influence the classification of MDR in Gram-negative bacteria.
  • Clinical laboratories should be aware of these changes for accurate patient management.

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