In vitro synergy and selection of resistance by fluoroquinolones plus amikacin or β-lactams against extended-spectrum β-lactamase-producing Escherichia coli

L. Drago, E. De Vecchi, L. Nicola, D. Legnani, A. Lombardi, M. R. Gismondo

Research output: Contribution to journalArticle

Abstract

This study compared the potential synergy of levofloxacin and ciprofloxacin in combination with cefepime, ceftazidime, imipenem, piperacillin/tazobactam or amikacin, against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli by using checkerboard and time kill studies. Moreover, selection of resistance was determined by frequency of mutations and by calculating the increase in minimum inhibitory concentrations (MICs) after five serial subcultures on antibiotic-containing plates. Synergy occurred more often with levofloxacin combined with imipenem (7/10 strains) and with levofloxacin or ciprofloxacin with amikacin (10/10) than for the other combinations. Time kill studies showed synergy for levofloxacin combined with amikacin, ceftazidime, imipenem or piperacillin/tazobactam, and for ciprofloxacin combined with amikacin, cefepime or imipenem. Antibiotic combinations selected for resistance less frequently than antibiotics alone. Mutation frequency was -12 for all combinations. In conclusion, the combination of a fluoroquinolone with a β-lactam or amikacin may provide improved antimicrobial activity and help limit the occurrence of resistance in ESBL-producing E. coli strains.

Original languageEnglish
Pages (from-to)46-53
Number of pages8
JournalJournal of Chemotherapy
Volume17
Issue number1
Publication statusPublished - Feb 2005

Keywords

  • β-lactams
  • Amikacin
  • Ciprofloxacin
  • Escherichia coli
  • Fluoroquinolones
  • Levofloxacin
  • Resistance
  • Synergy

ASJC Scopus subject areas

  • Microbiology (medical)
  • Pharmacology (medical)

Fingerprint Dive into the research topics of 'In vitro synergy and selection of resistance by fluoroquinolones plus amikacin or β-lactams against extended-spectrum β-lactamase-producing Escherichia coli'. Together they form a unique fingerprint.

  • Cite this