Episode Summary

Susceptibility testing for piperacillin-tazobactam has undergone rapid evolution, largely driven by some surprising results from the MERINO trial, which compared the efficacy of piperacillin-tazobactam and meropenem for treatment of patients with ceftriaxone-resistant E. coli or Klebsiella pneumoniae bacteremia. We discuss how the results of the MERINO trial led to reconsideration of breakpoints for pipercillin-tazobactam at the Clinical Laboratory Standards Institute, or CLSI, how the breakpoints were changed, and how well commercial platforms perform piperacillin-tazobactam testing using FDA or CLSI breakpoints. Spoiler alert: the news isn’t great.

If you are interested in beta-lactam/beta lactamase combinations, you should check out the previous episode of this podcast, hosted by our friend Dr. Cesar Arias, the Editor-in-Chief of Antimicrobial Agents and Chemotherapy. Cesar and the guests did a great review of recent developments in this fast-moving area.


  • Dr. Trish Simner - Director of the Medical Bacteriology and Infectious Disease Sequencing Laboratories, Johns Hopkins Hospital
  • Dr. Romney Humphries - Director of the Division of Laboratory Medicine and the Medical Director of the Microbiology Laboratory at Vanderbilt University Medical Center.

This episode of Editors in Conversation is brought to you by the Journal of Clinical Microbiology and hosted by JCM Editor in Chief, Alex McAdam and Dr. Elli Theel. JCM is available at https://jcm.asm.org and on https://twitter.com/JClinMicro.

Visit journals.asm.org/journal/jcm to read articles and/or submit a manuscript.

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