Evaluation of Piperacillin-Tazobactam Testing against <i>Enterobacterales</i> by the Phoenix, MicroScan, and Vitek2 Tests Using Updated Clinical and Laboratory Standards Institute Breakpoints
Carmila Manuel, Richard Maynard, April N. Abbott, Kara Adams, Kevin Alby, Amy Sweeney, Jennifer Dien Bard, Irvin Ibarra Flores, Violet Rekasius, Amanda Harrington, Tiffany S. Kidd, Amy J. Mathers, Tsigereda Tekle, Patricia J. Simner, Romney M. Humphries
Abstract
= 62 isolates) demonstrated 95.2% CA, 6.3% VMEs, and 0.0% MEs by CLSI and 96.8% CA, 0.0% VMEs, and 2.2% MEs by FDA breakpoints. Overall, the performance of the test systems was not substantially different using CLSI breakpoints off-label than using on-label FDA breakpoints. However, limitations were noted with higher-than-desired VME rates (all three systems) and lower-than-desired CA (MicroScan and Phoenix). Laboratories should consider adoption of the revised CLSI breakpoints with automated test systems but be aware that some performance challenges exist for testing TZP on automated systems, regardless of breakpoints applied.