title: In vitro pharmacodynamic properties of colistin methanesulfonate and amikacin against Pseudomonas aeruginosa.
abstract: OBJECTIVE
  In vitro pharmacodynamic properties of colistin methanesulfonate and amikacin were investigated by studying time-kill kinetics and post-antibiotic effect (PAE) against strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis.
  
  
  METHODS
  Synergy was investigated at 0.5 ×, 1 × and 5 × MIC of antibiotics using time-kill curve method. PAEs were determined by the standard viable counting method where bacteria in the logarithmic phase of growth were exposed for 1 h to the antibiotics at 1 × or 20 × MIC, alone and in combinations. Synergy and additive effects were detected at 1 × MIC, at 24 h.
  
  
  RESULTS
  Some of the strains produced an earlier synergistic effect at 12 h. No antagonism was observed. Colistin methanesulfonate and amikacin produced PAEs 1.16 ± 0.10 to 2.25 ± 0.16 h and 0.96 ± 0.15 to 2.69 ± 0.32 h, respectively. When the antibiotics were used in combination the PAEs were prolonged to a value of 3.88 ± 0.25 h. Consequently, the
  
  
  CONCLUSIONS
  Findings of this study may play useful role in selecting the appropriate combinations when a single agent is inadequate, and may have important information for optimizing the dose intervals.
authors.affiliation: Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Istanbul University, 34116 Beyazit, Istanbul, Turkey. caglabozkurt@hotmail.com
authors.forename: C
authors.initials: C
authors.lastname: Bozkurt-Guzel
authors.forename: A A
authors.initials: AA
authors.lastname: Gerceker
mesh_terms: D000583:Amikacin / Q000493:pharmacokinetics* / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D003091:Colistin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000150:complications; D004347:Drug Interactions; D004359:Drug Therapy, Combination / Q000379:methods; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D000583:Amikacin; C004691:colistinmethanesulfonic acid; D003091:Colistin