title: In vitro susceptibility of tigecycline against multidrug-resistant gram-negative strains: Etest versus agar dilution.
abstract: OBJECTIVE
  Tigecycline is a semi-synthetic tetracycline with activity against most multidrug-resistant (MDR) bacteria.
  
  
  METHODS
  We studied in vitro activity of tigecycline by agar dilution (AD) and Etest methods to evaluate their correlation. The study included 206 isolates of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, Klebsiella pneumoniae and MDR Acinetobacter baumannii recovered from blood cultures of patients of Baskent University between 2008 and 2010.
  
  
  RESULTS
  ESBL-producing E. coli had MIC50/MIC90 values of 0.5/0.5 µg/ml by AD and 0.25/0.5 µg/ml by Etest. ESBL-producing K. pneumoniae had MIC50/MIC90 values of 1/2 µg/ml by AD and 0.75/2 µg/ml by Etest, whereas MDR A. baumannii had MIC50/MIC90 values of 4/4 µg/ml by AD and 2/4 µg/ml by Etest. The correlation between AD and Etest was weak for ESBL-producing E. coli and strong for ESBL-producing K. pneumoniae and MDR A. baumannii. Tigecycline MIC values for ESBL-producing E. coli were lower than the tigecycline concentration, while they were higher than the concentrations attainable by treatment doses for A. baumannii.
  
  
  CONCLUSIONS
  Tigecycline is an appropriate agent in the treatment of E. coli bacteremia, but it is not for treating A. baumannii bacteremia. Tigecycline could be used for K. pneumoniae bacteremia treatment after determining its MIC value. Determining the MIC value by gold-standard methods is more appropriate due to the correlation between Etest and AD at high MIC values.
authors: Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, Baskent University, Ankara, Turkey.
authors: Sezen
authors: S
authors: Özkök
authors: Turhan
authors: T
authors: Togan
authors: Ayşegül
authors: A
authors: Yesilkaya
authors: Funda
authors: F
authors: Timurkaynak
authors: Özlem Kurt
authors: ÖK
authors: Azap
authors: Hande
authors: H
authors: Arslan
mesh_terms: D000362:Agar / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000188:drug therapy; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D000078304:Tigecycline
chemical_list: D000900:Anti-Bacterial Agents; D000078304:Tigecycline; D000362:Agar; D008911:Minocycline