Comparative Evaluation of Tigecycline Susceptibility Testing Methods for Expanded-Spectrum Cephalosporin- and Carbapenem-Resistant Gram-Negative Pathogens |
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| Authors: | Olympia Zarkotou Spyros Pournaras George Altouvas Vassiliki Pitiriga Maria Tziraki Vassiliki Mamali Katerina Themeli-Digalaki Athanassios Tsakris |
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| Institution: | aDepartment of Microbiology, Tzaneio General Hospital, Piraeus, Greece ;bDepartment of Microbiology, Medical School, University of Thessaly, Larissa, Greece ;cDepartment of Microbiology, Medical School, University of Athens, Athens, Greece |
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| Abstract: | We evaluated the Vitek2, Etest, and MIC Test Strip (MTS) methods of tigecycline susceptibility testing with 241 expanded-spectrum cephalosporin-resistant and/or carbapenem-resistant Enterobacteriaceae and Acinetobacter baumannii clinical isolates by using dry-form broth microdilution (BMD) as the reference method. The MIC50/90s were as follows: BMD, 1/4 μg/ml; Vitek2, 4/≥8 μg/ml; Etest, 2/4 μg/ml; MTS, 0.5/2 μg/ml. Vitek2 produced 9.1/21.2% major errors, Etest produced 0.4/0.8% major errors, and MTS produced no major errors but 0.4/3.3% very major errors (FDA/EUCAST breakpoints). Vitek2 tigecycline results require confirmation by BMD or Etest for multidrug-resistant pathogens. |
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