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BioMed Research International
Volume 2014 (2014), Article ID 397421, 6 pages
Research Article

Effects of Various Antibiotics Alone or in Combination with Doripenem against Klebsiella pneumoniae Strains Isolated in an Intensive Care Unit

1Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Istanbul University, Beyazit, 34116 Istanbul, Turkey
2Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, University of Istanbul Medipol, 34083 Istanbul, Turkey

Received 4 July 2014; Accepted 1 September 2014; Published 28 October 2014

Academic Editor: Abdelwahab Omri

Copyright © 2014 Berna Ozbek Celik et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Colistin, tigecycline, levofloxacin, tobramycin, and rifampin alone and in combination with doripenem were investigated for their in vitro activities and postantibiotic effects (PAEs) on Klebsiella pneumoniae. The in vitro activities of tested antibiotics in combination with doripenem were determined using a microbroth checkerboard technique. To determine the PAEs, K. pneumoniae strains in the logarithmic phase of growth were exposed for 1 h to antibiotics, alone and in combination. Recovery periods of test cultures were evaluated using viable counting after centrifugation. Colistin, tobramycin, and levofloxacin produced strong PAEs ranging from 2.71 to 4.23 h, from 1.31 to 3.82 h, and from 1.35 to 4.72, respectively, in a concentration-dependent manner. Tigecycline and rifampin displayed modest PAEs ranging from 1.18 h to 1.55 h and 0.92 to 1.19, respectively. Because it is a beta-lactam, PAEs were not exactly induced by doripenem (ranging from 0.10 to 0.18 h). In combination, doripenem scarcely changed the duration of PAE of each tested antibiotic alone. The findings of this study may have important implications for the timing of doses during K. pneumoniae therapy with tested antibiotics.