The number of carbapenem-resistant Acinetobacter baumannii isolates significantly increased in our hospital from 2002 to 2006. Twenty-eight clinical isolates of carbapenem-resistant A. baumannii were collected between January and September 2007. Isoelectric focusing and polymerase chain reaction (PCR) experiments were used for preliminary identification of the carbapenem-resistant beta-lactamases. They were further identified by DNA sequencing. All of the isolates harbored blaOXA-66(100%) and twenty-six (92.9%) of the isolates were found to produce blaOXA-23. ISAba1 in upstream of blaOXA23 and blaOXA-66 were detected in 25 isolates and 28 isolates respectively. Typing of strains was performed using pulsed-field gel electrophoresis (PFGE), and 16 different genotypes were identified. Four clusters were identified and designated A, B, C and D according to the published interpretation criteria. Forteen isolates belonged to cluster A, and eight isolates belonged to cluster C. Our results indicate that the increase in the number of carbapenem-resistant beta-lactamase-producing A. baumannii isolates in our hospital is due mainly to the dissemination of a cluster A epidemiologic strain with OXA-23 beta-lactamase.
