1998. Outcomes of Patients with Amp-C Inducible Enterobacteriaceae infections Treated with Carbapenems versus Cefepime or Piperacillin-tazobactam
Session: Poster Abstract Session: Antimicrobial Resistance Mechanisms
Saturday, October 29, 2016
Room: Poster Hall
  • Carb vs. cefe and PT - BSI and PNA - ID Week.pdf (96.2 kB)
  • Background: Enterobacter spp., S. marcescens, C. freundii, Providencia spp., and M. morganii (ESCPM) contain a chromosomally located, inducible AmpC beta-lactamases, a unique mechanism of resistance. Carbapenems (CARB) and cefepime (CEF) are stable against inducible or constitutive AmpC expression. Piperacillin/tazobactam (PT) is not stable, but is not a strong AmpC inducer. Optimal therapy for these infections is unknown. We compared clinical outcomes between patients with ESCPM infections treated with CARB vs. CEF or PT.

    Methods: Retrospective chart review of patients with ESCPM infections stratified by empiric CARB vs. CEF or PT. Patients had respiratory or blood cultures positive for beta-lactam susceptible ESPCM pathogens and were admitted to the hospital between January 1, 2012-January 1, 2015. The primary outcome was clinical failure. Secondary outcomes included 30-day readmission and mortality. Fisher’s exact test, 2-sided was used for statistical analysis, and significance was defined as a p-value <0.05.

    Results: Analysis included 187 patients (CARB n=30 vs. CEF/PT n=157). The most common site of infection was respiratory (CARB 53.3% vs. CEF/PT 56.7%). At the start of antibiotics, severity of illness was similar: intensive care unit (ICU) admission (CARB 73.2% vs. CEF/PT 73.3%), receipt of mechanical ventilation (CARB 52.9% vs. CEF/PT 56.7%), and receipt of vasopressor agents (CARB 27.4%, CEF/PT 23.3%). All other baseline characteristics were similar between groups. The primary outcome of clinical failure in the CARB group was 13.3% vs. 26.8% in the CEF/PT, p=0.164. Rates of clinical failure for patients in the CARB group were lower in a subgroup of 137 ICU patients (CARB 9.1% vs. 29.6% (p=0.046). 30-day readmission was lower in the CARB group (8.7%) compared to CEF/PT (17.8%) but was not statistically significant (p=0.368) and 30-day morality was similar (CARB 24.8% vs. CEF/PT 23.3%, p=1.00).

    Conclusion: Among 137 patients in ICU at start of empiric therapy, 2/22 (9.1%) of those treated with CARB had clinical failure, vs. 34/115 (29.6%) of patients treated with CEF/PT (P=0.03). A study with a larger sample size would be needed to determine if the trend is significant in the overall patient population.

    Meghan Jeffres, PharmD1, Clayton Foster, MD2, Bruce Mccollister, MD3, Randolph Fujit, PharmD4, Mary Bessesen, MD4 and Michelle Barron, MD5, (1)Department of Clinical Pharmacy, University of Colorado Skaggs School of Pharmacy, Aurora, CO, (2)Division of Infectious Diseases, University of Colorado, Aurora, CO, (3)Division of Infectious Diseases, University of Colorado Denver, Aurora, CO, (4)VA Eastern Colorado Healthcare System, Denver, CO, (5)Internal Medicine/Infectious Diseases, University of Colorado Denver, Aurora, CO


    M. Jeffres, None

    C. Foster, None

    B. Mccollister, None

    R. Fujit, None

    M. Bessesen, None

    M. Barron, None

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