title: Antimicrobial activity of subinhibitory concentrations of ciprofloxacin against Pseudomonas aeruginosa as determined by the killing curve method and the postantibiotic effect.
abstract: This investigation used the postantibiotic effect (PAE) and killing curves to examine the antimicrobial activity of subinhibitory (1/8x, 1/4x and 1/2x MIC) and inhibitory (1x MIC) concentrations of ciprofloxacin against mucoid (M) and nonmucoid (NM) urinary isolates of Pseudomonas aeruginosa. Subinhibitory concentrations (1/8x, 1/4x and 1/2x MIC) of ciprofloxacin produced PAEs with no difference between M and NM strains. For NM strains, those with low MICs (< or = 1.0 mg/l) to ciprofloxacin produced significantly longer PAEs than isolates with high MICs (> 1 mg/l). Killing curve studies demonstrated that subinhibitory concentrations of ciprofloxacin produce little effect (1/8x MIC) or stasis (1/4x and 1/2x MIC) of growth for several hours. Only 1x MIC was bactericidal for several strains. At 1/2x and 1x MIC, bacterial inhibition was greater against NM versus M isolates. The M phenotype of P. aeruginosa reduces killing by ciprofloxacin but not the PAE.
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
authors.forename: G G
authors.initials: GG
authors.lastname: Zhanel
authors.forename: J
authors.initials: J
authors.lastname: Crampton
authors.forename: S
authors.initials: S
authors.lastname: Kim
authors.forename: L E
authors.initials: LE
authors.lastname: Nicolle
authors.forename: R J
authors.initials: RJ
authors.lastname: Davidson
authors.forename: D J
authors.initials: DJ
authors.lastname: Hoban
mesh_terms: D002939:Ciprofloxacin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects*
chemical_list: D002939:Ciprofloxacin