Clonal Change of blaSIM-1-Carrying Acinetobacter spp. from 2003 to 2008 in the Hospital Where It Was Initially Discovered

Abstract

SIM-1 metallo-β-lactamase was first discovered from carbapenem-resistant Acinetobacter spp. isolated in a Korean University Hospital in 2003, and was recently reported to have been discovered in A. baylyi isolated in nearby China. The aims of this study were to reveal clonal changes in bla(SIM-1)-harboring Acinetobacter isolates collected from 2003 to 2008 in the same Korean hospital, where they were first discovered to gain further insight into the relation between bla(SIM-1)-harboring plasmids and Acinetobacter spp. Among 1,761 nonduplicated imipenem-resistant Acinetobacter spp. isolates, 29 isolates were identified as bla(SIM-1) carriers. They were categorized into nine types according to pulsed-field gel electrophoresis findings. While most bla(SIM-1)-carrying isolates from 2003 to 2005 belonged to A. pittii, those from 2006 to 2007 were mostly isolates of A. nosocomialis. Most of the bla(SIM-1) genes were carried on ca. 280-kb plasmids and were only discovered in non-baumannii Acinetobacter spp. Integrons carrying the bla(SIM-1) gene were identical in structure in all species. These findings suggest that the plasmids were transferable, but not promiscuous. Further surveillance should be continued to detect and control further spread of the bla(SIM-1) gene, as the appearance of the bla(SIM-1) gene in different Acinetobacter spp. in different countries has already begun.