title: In vitro efficacy of levofloxacin alone or in combination tested against multi-resistant Pseudomonas aeruginosa strains.
abstract: Levofloxacin, the S(-) isomer of ofloxacin, demonstrates in vitro activity against Pseudomonas aeruginosa. To further characterize this activity, levofloxacin was tested against three populations of recent clinical isolates categorized by their resistance patterns to several other anti-pseudomonal agents. Results demonstrate the minimum inhibitory concentrations (MICs) for levofloxacin were generally two- to fourfold higher than for ciprofloxacin. Higher fluoroquinolone MICs were associated with MIC increases in other drugs. Levofloxacin demonstrated cross resistance against ciprofloxacin-resistant strains. Combinations of levofloxacin and several codrugs revealed that the majority of evaluable interactions demonstrated indifferent action. Levofloxacin exhibited enhanced activity (additive or degrees of synergy) principally with piperacillin, aztreonam, or ceftazidime. The synergy and additive rate (21 to 30%) compared favorably with the enhanced interactions observed with gentamicin combined with piperacillin or ceftazidime (27 to 30%). Levofloxacin activity against P. aeruginosa was most comparable to that of ciprofloxacin, which was applicable against > 90% of strains found to be resistant to other classes of antimicrobial agents.
authors.affiliation: Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Flynn
authors.forename: D M
authors.initials: DM
authors.lastname: Johnson
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001398:Aztreonam / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D010878:Piperacillin / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D014031:Tobramycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D005839:Gentamicins; D002939:Ciprofloxacin; D064704:Levofloxacin; D015378:Imipenem; D002442:Ceftazidime; D015242:Ofloxacin; D001398:Aztreonam; D014031:Tobramycin; D010878:Piperacillin