title: Frequent emergence of porin-deficient subpopulations with reduced carbapenem susceptibility in ESBL-producing Escherichia coli during exposure to ertapenem in an in vitro pharmacokinetic model.
abstract: OBJECTIVE
  Ertapenem resistance is increasing in Enterobacteriaceae. The production of extended-spectrum β-lactamases (ESBLs) and reduced expression of outer membrane porins are major mechanisms of resistance in ertapenem-resistant Klebsiella pneumoniae. Less is known of ertapenem resistance in Escherichia coli. The aim of this study was to explore the impact of ESBL production in E. coli on the antibacterial activity of ertapenem.
  
  
  METHODS
  Two E. coli strains, with and without ESBL production, were exposed to ertapenem in vitro for 48 h at concentrations simulating human pharmacokinetics with conventional and higher dosages.
  
  
  RESULTS
  Isolates with non-susceptibility to ertapenem (MICs 0.75-1.5 mg/L) were detected after five of nine time-kill experiments with the ESBL-producing strain. All of these isolates had ompR mutations, which reduce the expression of outer membrane porins OmpF and OmpC. Higher dosage did not prevent selection of porin-deficient subpopulations. No mutants were detected after experiments with the non-ESBL-producing strain. Compared with other experiments, experiments with ompR mutants detected in endpoint samples showed significantly less bacterial killing after the second dose of ertapenem. Impaired antibacterial activity against E. coli with ESBL production and ompR mutation was also demonstrated in time-kill experiments with static antibiotic concentrations.
  
  
  CONCLUSIONS
  The combination of ESBL production and porin loss in E. coli can result in reduced susceptibility to ertapenem. Porin-deficient subpopulations frequently emerged in ESBL-producing E. coli during exposure to ertapenem at concentrations simulating human pharmacokinetics. Inappropriate use of ertapenem should be avoided to minimize the risk of selection of ESBL-producing bacteria with reduced susceptibility to carbapenems.
authors.affiliation: Department of Medical Sciences, Section of Infectious Diseases, Uppsala University, Uppsala, Sweden. thomas.tangden@gmail.com
authors.forename: Thomas
authors.initials: T
authors.lastname: Tängdén
authors.forename: Marlen
authors.initials: M
authors.lastname: Adler
authors.forename: Otto
authors.initials: O
authors.lastname: Cars
authors.forename: Linus
authors.initials: L
authors.lastname: Sandegren
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Löwdin
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D058491:Bacterial Load; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D015780:Carbapenems / Q000493:pharmacokinetics / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D000077727:Ertapenem; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D018272:Porins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics; D001618:beta-Lactamases / Q000378:metabolism*; D047090:beta-Lactams / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D015780:Carbapenems; C109237:OmpF protein; D018272:Porins; D015534:Trans-Activators; D047090:beta-Lactams; C112177:osmolarity response regulator proteins; D001618:beta-Lactamases; D000077727:Ertapenem
keywords: ESBLs; outer membrane porins; resistance