From detection to decision: how laboratory testing and reporting strategies can shape management of carbapenemase-producing Enterobacterales infections

Antimicrobial resistance mediated by carbapenemases significantly complicates treatment options. A case report by Morelan et al. (ASM Case Reports 1:e00094-25, 2025, https://doi.org/10.1128/asmcr.00094-25 ) illustrates how delayed recognition of Klebsiella pneumoniae carbapenemase (KPC) production in an Escherichia coli urinary tract infection resulted in suboptimal cefepime therapy, despite in vitro susceptibility. This case underscores the urgent need for clinical laboratories to implement on-site carbapenemase testing, as recommended by the Infectious Diseases Society of America and the Clinical and Laboratory Standards Institute (CLSI). Timely detection of KPC, coupled with reporting strategies for cefepime susceptibility results (suppression or editing results as resistant) in carbapenemase producers, may have facilitated earlier administration of a more appropriate antimicrobial and prevented recurrent infections and readmissions. In this commentary, we highlight recent updates to CLSI guidance for carbapenemase testing and antimicrobial susceptibility reporting strategies. Using this case report as an example, we outline the potential impact of these strategies on patient management and outcomes, further emphasizing the role of the clinical microbiology laboratory in antimicrobial stewardship.