Strategies for Updating Piperacillin-Tazobactam Breakpoints.

In this issue of the Journal of Clinical Microbiology , C. Manuel, R. Maynard, A. Abbott, K. Adams, et al. (J Clin Microbiol 61:e01617-22, 2023, https://doi.org/10.1128/JCM.01617-22) describe a multisite study evaluation of piperacillin-tazobactam (TZP) MIC testing on three U.S. Food and Drug Administration (FDA)-cleared antimicrobial susceptibility testing (AST) devices compared to the reference broth microdilution method for organisms belonging to Enterobacterales . Although overall performance of each of the three devices was comparable when applying either FDA or Clinical and Laboratory Standards Institute (CLSI) TZP breakpoints, failure to update to the current CLSI breakpoints may result in falsely categorizing as many as 20% of the TZP-resistant isolates as susceptible. The impact of not updating clinical breakpoints and strategies for implementation of updated breakpoints are discussed.