Pharmacodynamic activity of ertapenem versus genotypically characterized extended-spectrum β-lactamase (ESBL)-, KPC- or NDM-producing Escherichia coli with reduced susceptibility or resistance to ertapenem using an in vitro model

J Antimicrob Chemother. 2014 Sep;69(9):2448-52. doi: 10.1093/jac/dku149. Epub 2014 May 14.


Objectives: We assessed the pharmacodynamic activity of ertapenem against Escherichia coli with reduced susceptibility (MIC 0.12-0.5 mg/L), intermediate resistance (MIC 1.0 mg/L) or resistance (MIC ≥ 2 mg/L) to ertapenem using an in vitro model.

Methods: Fifteen extended-spectrum β-lactamase- or carbapenemase-producing E. coli were studied. The in vitro pharmacodynamic model was inoculated with ∼1 × 10(6) cfu/mL and ertapenem was dosed once daily at 0 and 24 h to simulate free (ƒ) Cmax and t½ obtained after either 1 g or 2 g intravenous once-daily doses in healthy volunteers (1 g: ƒCmax 15 mg/L, t½ 4 h). Sampling was performed over 48 h to assess viable growth and resistance selection.

Results: An ertapenem T> MIC ≥ 75.4% (ertapenem MICs ≤ 0.5 mg/L) resulted in bactericidal (≥ 3 log10 killing) activity against all strains. An ertapenem T>MIC of 61% was bactericidal at 6 and 12 h but regrowth at 24 and 48 h occurred in some strains. An ertapenem T>MIC of 13%-43% was bactericidal at 6 h but regrowth (with MIC increases) occurred. No inhibition of an NDM strain with an ertapenem T>MIC of 0% (ertapenem MIC 256 mg/L) occurred at any timepoint.

Conclusions: Once-daily dosing with 1 g of ertapenem was bactericidal against ESBL-producing E. coli with ertapenem MICs ≤ 0.5 mg/L and was bactericidal against strains with MICs of 1.0 mg/L, with regrowth in some strains. Ertapenem MICs of 2-8 mg/L resulted in early bactericidal activity followed by regrowth. Once-daily dosing with 2 g of ertapenem was bactericidal against strains with an MIC of 1.0 mg/L, but regrowth occurred in some strains with an ertapenem MIC of 2 mg/L.

Keywords: E. coli; PD; antimicrobial.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / pharmacokinetics
  • Anti-Bacterial Agents / pharmacology*
  • Ertapenem
  • Escherichia coli / drug effects*
  • Escherichia coli / enzymology
  • Humans
  • Microbial Sensitivity Tests
  • Microbial Viability / drug effects
  • beta-Lactam Resistance*
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism*
  • beta-Lactams / administration & dosage
  • beta-Lactams / pharmacokinetics
  • beta-Lactams / pharmacology*


  • Anti-Bacterial Agents
  • beta-Lactams
  • beta-Lactamases
  • Ertapenem