Comparative bactericidal activity of fluoroquinolones against clinical isolates resistant to fluoroquinolones

Lorenzo Drago, E. De Vecchi, L. Nicola, M. Valli, F. Marchetti, M. R. Gismondo

Research output: Contribution to journalArticlepeer-review


The bactericidal activity of levofloxacin, ciprofloxacin, moxifloxacin and norfloxacin against clinical isolates conventionally classified as resistant to fluoroquinolones were compared at their maximum concentrations in serum, urine (except moxifloxacin) and bronchial mucosa (except norfloxacin). Time killing curves against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Streptococcus pneumoniae were performed. Serum concentrations of the tested drugs were not able to produce a bactericidal effect on fluoroquinolone-resistant strains. In the urine series, levofloxacin was always bactericidal (decrease ≥3 logs CFU/ml), while norfloxacin and ciprofloxacin were bactericidal on E. coli (both), P. mirabilis (norfloxacin) and P. aeruginosa (ciprofloxacin). In the bronchial mucosa series, S. pneumoniae was rapidly killed by levofloxacin and moxifloxacin, and K. pneumoniae by levofloxacin after 12 hours. In conclusion, the maximum levofloxacin concentrations achievable at certain body sites allowed killing even of strains defined as resistant by conventional breakpoints.

Original languageEnglish
Pages (from-to)118-123
Number of pages6
JournalJournal of Chemotherapy
Issue number2
Publication statusPublished - Apr 2003


  • Ciprofloxacin
  • Gram-negative bacteria
  • Gram-positive bacteria
  • Levofloxacin
  • Moxifloxacin
  • Norfloxacin

ASJC Scopus subject areas

  • Pharmacology (medical)
  • Microbiology (medical)


Dive into the research topics of 'Comparative bactericidal activity of fluoroquinolones against clinical isolates resistant to fluoroquinolones'. Together they form a unique fingerprint.

Cite this