Effect of Resistance Mechanisms on the Inoculum Effect of Carbapenem in Klebsiella pneumoniae Isolates with Borderline Carbapenem Resistance

Antimicrob Agents Chemother. 2015 Aug;59(8):5014-7. doi: 10.1128/AAC.00533-15. Epub 2015 May 18.


We aimed to examine the effects of resistance mechanisms on several resistance phenotypes among carbapenem-resistant Klebsiella pneumoniae isolates with borderline carbapenem MICs. We compared carbapenemase-negative K. pneumoniae with carbapenemase-producing K. pneumoniae (CPKP) isolates with similar MICs. CPKP isolates exhibited a marked inoculum effect and were more resistant to the bactericidal effect of meropenem. This suggests that MIC measurements alone may not be sufficient in predicting the therapeutic efficacy of carbapenems against CPKP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Carbapenems / pharmacology*
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Humans
  • Klebsiella Infections / drug therapy
  • Klebsiella pneumoniae / drug effects
  • Klebsiella pneumoniae / genetics*
  • Klebsiella pneumoniae / isolation & purification
  • Klebsiella pneumoniae / metabolism
  • Microbial Sensitivity Tests
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Carbapenems
  • beta-Lactamases
  • carbapenemase