Meropenem Versus Piperacillin-Tazobactam for Definitive Treatment of Bloodstream Infections Caused by AmpC β-Lactamase-Producing Enterobacter spp, Citrobacter freundii, Morganella morganii, Providencia spp, or Serratia marcescens: A Pilot Multicenter Randomized Controlled Trial (MERINO-2)

Adam G. Stewart, David L. Paterson, Barnaby Young, David C. Lye, Joshua S. Davis, Kellie Schneider, Mesut Yilmaz, Rumeysa Dinleyici, Naomi Runnegar, Andrew Henderson, Sophia Archuleta, Shirin Kalimuddin, Brian M. Forde, Mark D. Chatfield, Michelle J. Bauer, Jeffrey Lipman, Tiffany Harris-Brown, Patrick N.A. Harris

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    Abstract

    Background: Carbapenems are recommended treatment for serious infections caused by AmpC-producing gram-negative bacteria but can select for carbapenem resistance. Piperacillin-tazobactam may be a suitable alternative. 

    Methods: We enrolled adult patients with bloodstream infection due to chromosomal AmpC producers in a multicenter randomized controlled trial. Patients were assigned 1:1 to receive piperacillin-tazobactam 4.5 g every 6 hours or meropenem 1 g every 8 hours. The primary efficacy outcome was a composite of death, clinical failure, microbiological failure, and microbiological relapse at 30 days. 

    Results: Seventy-two patients underwent randomization and were included in the primary analysis population. Eleven of 38 patients (29%) randomized to piperacillin-tazobactam met the primary outcome compared with 7 of 34 patients (21%) in the meropenem group (risk difference, 8% [95% confidence interval {CI},-12% to 28%]). Effects were consistent in an analysis of the per-protocol population. Within the subcomponents of the primary outcome, 5 of 38 (13%) experienced microbiological failure in the piperacillin-tazobactam group compared to 0 of 34 patients (0%) in the meropenem group (risk difference, 13% [95% CI, 2% to 24%]). In contrast, 0% vs 9% of microbiological relapses were seen in the piperacillin-tazobactam and meropenem arms, respectively. Susceptibility to piperacillin-tazobactam and meropenem using broth microdilution was found in 96.5% and 100% of isolates, respectively. The most common AmpC β-lactamase genes identified were blaCMY-2, blaDHA-17, blaCMH-3, and blaACT-17. No ESBL, OXA, or other carbapenemase genes were identified. 

    Conclusions: Among patients with bloodstream infection due to AmpC producers, piperacillin-tazobactam may lead to more microbiological failures, although fewer microbiological relapses were seen. 

    Clinical Trials Registration: NCT02437045.

    Original languageEnglish
    Article numberofab387
    Pages (from-to)1-12
    Number of pages12
    JournalOpen Forum Infectious Diseases
    Volume8
    Issue number8
    DOIs
    Publication statusPublished - 1 Aug 2021

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