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Cefazolin and enterobacteriaceae: rationale for revised susceptibility testing breakpoints.

John D Turnidge1,

  • 1SA Pathology at Women's and Children's Hospital, North Adelaide, 5006, and School of Molecular and Biomedical Sciences, University of Adelaide, Adelaide, Australia. john.turnidge@health.sa.gov.au

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|March 24, 2011
PubMed
Summary
This summary is machine-generated.

The Clinical and Laboratory Standards Institute updated cefazolin breakpoints for Enterobacteriaceae. New criteria, based on recent data, adjust minimum inhibitory concentrations and improve disk diffusion correlations for better antimicrobial susceptibility testing.

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Area of Science:

  • Microbiology
  • Clinical Pharmacy
  • Infectious Diseases

Background:

  • The Clinical and Laboratory Standards Institute (CLSI) previously established breakpoints for cefazolin against Enterobacteriaceae in January 2010.
  • These breakpoints were based on available in vitro data, pharmacokinetic-pharmacodynamic (PK-PD) properties, and clinical outcomes at that time.

Purpose of the Study:

  • To revise the CLSI cefazolin breakpoints for Enterobacteriaceae based on updated scientific evidence.
  • To align interpretive criteria with current antimicrobial activity, PK-PD data, and clinical outcome studies.
  • To establish reliable disk diffusion zone diameter correlates for the revised breakpoints.

Main Methods:

  • Re-evaluation of in vitro antimicrobial activity data for cefazolin against Enterobacteriaceae.
  • Analysis of pharmacokinetic-pharmacodynamic characteristics associated with cefazolin dosing.
  • Review of published clinical outcome studies related to cefazolin therapy for Enterobacteriaceae infections.
  • Development of new minimum inhibitory concentration (MIC) interpretive criteria and corresponding disk diffusion zone diameter correlates.

Main Results:

  • Revised CLSI breakpoints for cefazolin against Enterobacteriaceae will be published in January 2011.
  • The new breakpoints increase the MIC interpretive criteria by one 2-fold dilution.
  • These revised criteria are linked to an adult intravenous dosing regimen of 2 g every 8 hours.
  • Disk diffusion zone diameter correlates, previously undefined, can now be established with the new interpretive criteria.
  • Testing of cephalothin remains necessary for predicting susceptibility to oral cephalosporins like cefadroxil, cefpodoxime, cephalexin, and loracarbef.

Conclusions:

  • The revised CLSI breakpoints for cefazolin offer improved accuracy in antimicrobial susceptibility testing for Enterobacteriaceae.
  • The updated criteria facilitate more precise interpretation of cefazolin's efficacy in clinical settings.
  • Laboratories must adapt to the new breakpoints for accurate cefazolin susceptibility reporting, while continuing cephalothin testing for oral cephalosporin susceptibility prediction.