Acquired carbapenemases in Enterobactericeae in Singapore, 1996-2012

Abstract

Aims: To characterise carbapenemase-producing Enterobacteriaceae (CRE) isolated in Singapore. Methods: Carbapenemase genes and their flanking regions were amplified and sequenced by PCR. Isolates were typed by pulsed-field gel electrophoresis and multilocus sequence typing. Plasmids bearing carbapenemase genes were sized by S1 nuclease digestion, Southern blotting, and DNA hybridisation with appropriate probes. Transfer of these plasmids was attempted by conjugation and transformation. Successfully transferred plasmids were characterised by polymerase chain reaction (PCR) replicon typing and restriction digestion. Results: Isolates of Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae and Citrobacter species carried a variety of carbapenemase genes including blaIMP-1, blaIMP-4, blaNDM-1, blaNDM-7, blaOXA-181, blaOXA-48 and bla KPC-2. Apart from K. pneumoniae with blaOXA-181, and some K. pneumoniae with blaNDM-1, the other isolates were not clonal. However there appears to be some spread of plasmids with blaIMP-1, blaNDM-1, blaKPC-2, and blaOXA-48. Conclusions: The number of isolates of CRE has increased in Singapore, especially since 2010. There is a diversity of carbapenemase types that reflects the geographical proximity of other countries with CRE. © 2013 Royal College of Pathologists of Australasia.