Clonal spread of carbapenem-resistant OXA-72-positive Acinetobacter baumannii in a Croatian university hospital

Background: From July to October 2008, 34 Acinetobacter baumannii isolates were involved in an outbreak at the Clinical Hospital Center, Zagreb. The aim of this study was to characterize the mechanisms of carbapenem resistance in our A. baumannii isolates and determine their epidemiology. Methods: Antibiotic susceptibilities were determined by broth microdilution. PCR was used to detect the presence of carbapenemases. Genotyping of the isolates was performed by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and repetitive sequence-based PCR (rep-PCR). Results: Thirty-three carbapenem-resistant isolates were positive for the acquired bla(OXA-72) and one unrelated isolate was positive for bla(OXA-58). The bla(OXA-72)-positive isolates were shown to be clonally related by RAPD, rep-PCR, and PFGE. Conclusions: On the basis of susceptibility testing, beta-lactamase characterization, and genotyping of the isolates we can conclude that clonal spread of endemic isolates was responsible for the high frequency of OXA-72-positive multidrug-resistant A. baumannii in this setting. Most of the isolates originated from the intensive care unit indicating local dissemination within the hospital and pointing to the potential source of isolates. (C) 2011 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved