Abstract
In this issue of the Journal of Clinical Microbiology, S. García-Fernandez, Y. Bala, T. Armstrong, M. Garcia-Castillo, et al. (J Clin Microbiol 58:e01042-19, 2020, https://doi.org/10.1128/JCM.01042-19) describe the performance of a reformulated Etest for piperacillin-tazobactam. The analytical performance data are excellent, but in the face of recent emerging data on the inefficacy of piperacillin-tazobactam for certain organisms that test susceptible, the value of piperacillin-tazobactam MICs is controversial. Evaluation of MICs in the context of the modal MIC for Enterobacterales and Pseudomonas aeruginosa, the variability of MIC tests, and, possibly, resistance mechanisms is important to the optimum use of this antimicrobial.