title: In vitro efficacy of various antibiotic combinations against Pseudomonas aeruginosa isolates.
abstract: OBJECTIVE
  Pseudomonas aeruginosa is one of the leading causes of nosocomial infection. The present study tested the in vitro efficacy of ceftazidime or imipenem combined with amikacin, levofloxacin and colistin in P.aeruginosa isolates.
  
  
  METHODS
  P.aeruginosa strains, isolated from clinical samples, were assessed for antibiotic susceptibility using the disc diffusion method. Antibiotic combination tests were performed using minimum inhibitory concentration (MIC) test strips and the sum of the Fractional Inhibitory Concentration (ΣFIC) index was used to assess synergy.
  
  
  RESULTS
  Out of 60 isolated P.aeruginosa strains, 100% were susceptible to colistin and 26.7% (16 strains) were multidrug resistant. MIC50 and MIC90 values were 2 and 32 µg/ml for imipenem; 1.5 and 24 µg/ml for ceftazidime; 3 and 8 µg/ml for amikacin; 0.38 and 32 µg/ml for levofloxacin; 1 and 1.5 µg/ml for colistin, respectively. Antagonism was not found in any of the antibiotic combinations tested. The amikacin-ceftazidime combination was found to have a synergistic effect in 15% of the strains, but no synergistic effect was detected for other combinations.
  
  
  CONCLUSIONS
  In Pseudomonas infection, alternative treatment options using different antibiotic combinations should be tested in vitro and findings should be confirmed by clinical studies.
authors.affiliation: Department of Microbiology and Clinical Microbiology, Faculty of Medicine, Gaziantep University, Gaziantep, Turkey.
authors.forename: Ebru
authors.initials: E
authors.lastname: Nazli
authors.affiliation: Department of Microbiology and Clinical Microbiology, Faculty of Medicine, Gaziantep University, Gaziantep, Turkey yaseminzer@hotmail.com.
authors.forename: Yasemin
authors.initials: Y
authors.lastname: Zer
authors.affiliation: Department of Microbiology and Clinical Microbiology, Faculty of Medicine, Gaziantep University, Gaziantep, Turkey.
authors.forename: Fahriye
authors.initials: F
authors.lastname: Eksi
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D003091:Colistin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D064704:Levofloxacin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D064704:Levofloxacin; D015378:Imipenem; D000583:Amikacin; D002442:Ceftazidime; D003091:Colistin
keywords: Epsilometer test; Pseudomonas aeruginosa; synergy tests