title: Comparative in vitro activity of three fluoroquinolones against clinical isolates by E test.
abstract: The in vitro susceptibility of levofloxacin, ciprofloxacin and moxifloxacin against several gram-positive and gram-negative clinical isolates was tested by E test. We found that the MIC(50) and MIC(90) values against all members of the Enterobacteriaceae family except Serratia were <0.5 mg/l for ciprofloxacin and levofloxacin (MIC range 0.006-32 mg/l) based on the in vitro susceptibility data. The susceptibility rates for ciprofloxacin and levofloxacin were more than 85% for Escherichia coli, citrobacter, enterobacter cloacae, enterobacter aerogenes and Klebsiella pneumoniae, although Serratia and Acinetobacter exhibited more or less similar susceptibility rates (about 80%). Pseudomonas aeruginosa demonstrated significant resistance to fluoroquinolones (MIC(90) >32 mg/l) and decreased bactericidal rates (<65%) to levofloxacin and ciprofloxacin. Respiratory pathogens such as Streptococcus pneumoniae and Haemophilus influenzae were highly susceptible (100%) to levofloxacin and moxifloxacin. The ineffectiveness of fluoroquinolones for treating coagulase-positive Staphylococcus aureus was demonstrated by poor in vitro susceptibility rates with levofloxacin (52%) and moxifloxacin (57%). Coagulase-negative staphylococci demonstrated significantly decreased bactericidal rates to levofloxacin (21%), while the in vitro susceptibility to moxifloxacin was higher (66%) than that to levofloxacin. We propose that the beneficial effect of inclusion of any of these three fluoroquinolones in treating Enterococcus infections is marginal, as demonstrated by significantly reduced susceptibility rates (<32%). These data demonstrate the utility of fluoroquinoles to treat several gram-negative bacterial infections (with the exception of Acinetobacter and P. aeruginosa), as well as S. pneumoniae and H. influenzae.
authors.affiliation: Biotechnology, Immunology and Diagnostics Section, Center for Veterinary Biologics, Animal and Plant Health Inspection Services, United States Department of Agriculture, Ames, Iowa 50010, USA. kunaplui.t.madhusudhan@aphis.usda.gov
authors.forename: Kunapuli T
authors.initials: KT
authors.lastname: Madhusudhan
authors.forename: Carolyn
authors.initials: C
authors.lastname: Counts
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lody
authors.forename: Ophelia
authors.initials: O
authors.lastname: Carter
authors.forename: Sarah
authors.initials: S
authors.lastname: Dodson
authors.forename: Neelam
authors.initials: N
authors.lastname: Ojha
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001372:Aza Compounds; D002939:Ciprofloxacin / Q000494:pharmacology*; D024841:Fluoroquinolones; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D015242:Ofloxacin / Q000494:pharmacology*; D011804:Quinolines
chemical_list: D000890:Anti-Infective Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D002939:Ciprofloxacin; D064704:Levofloxacin; D015242:Ofloxacin; D000077266:Moxifloxacin