title: In vitro synergistic activity of colistin with tigecycline or β-lactam antibiotic/β-lactamase inhibitor combinations against carbapenem-resistant Acinetobacter baumannii.
abstract: OBJECTIVE
  Nosocomial infection caused by carbapenem-resistant Acinetobacter baumannii is a worldwide problem and treatment options remain controversial. This study investigated the in vitro effect of various antibiotic combinations against carbapenem-resistant A. baumannii strains.
  
  
  METHODS
  Antibiotic susceptibility of A. baumannii strains was analysed. In vitro synergistic efficacy of colistin combined with tigecycline, cefoperazone/sulbactam or piperacillin/tazobactam was tested against carbapenem-resistant A. baumannii strains. Synergy studies were performed using an eplisometer test-strip method.
  
  
  RESULTS
  Of the 50 carbapenem-resistant A. baumannii strains tested, 96% were susceptible to colistin and 64% were susceptible to tigecycline. Colistin-tigecycline, colistin-cefoperazone/sulbactam and colistin-piperacillin/tazobactam combinations were found to have synergistic effects against six (12%), two (4%), and one (2%), respectively, of the strains tested.
  
  
  CONCLUSIONS
  Colistin combined with tigecycline, cefoperazone/sulbactam or piperacillin/tazobactam revealed synergistic effects in some carbapenem-resistant A. baumannii strains. These results, together with the shortage of treatment options and the risk of developing resistance to colistin, suggest that clinicians should use colistin combined with other antibiotics or β-lactamase inhibitors when treating carbapenem-resistant A. baumannii infection.
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, Gaziantep University, Gaziantep, Turkey.
authors.forename: Ilkay
authors.initials: I
authors.lastname: Karaoglan
authors.forename: Yasemin
authors.initials: Y
authors.lastname: Zer
authors.forename: Vuslat Kecik
authors.initials: VK
authors.lastname: Bosnak
authors.forename: Ayse Ozlem
authors.initials: AO
authors.lastname: Mete
authors.forename: Mustafa
authors.initials: M
authors.lastname: Namiduru
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology; D002438:Cefoperazone / Q000494:pharmacology; D003091:Colistin / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004357:Drug Synergism; D006801:Humans; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives / Q000494:pharmacology; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D013407:Sulbactam / Q000494:pharmacology; D000078304:Tigecycline; D018440:beta-Lactam Resistance; D065093:beta-Lactamase Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D065093:beta-Lactamase Inhibitors; D000077725:Piperacillin, Tazobactam Drug Combination; D000078304:Tigecycline; D002438:Cefoperazone; D010397:Penicillanic Acid; D008911:Minocycline; D013407:Sulbactam; D010878:Piperacillin; D003091:Colistin
keywords: Acinetobacter baumannii; cefoperazone/sulbactam; colistin; combination therapy; eplisometer test; piperacillin/tazobactam; synergistic effect; tigecycline