Spread of plasmids containing the blaVIM-1 and blaCTX-M genes and the qnr determinant in enterobacter cloacae, klebsiella pneumoniae and klebsiella oxytoca isolates

Abstract

Objectives: We describe 12 VIM-1-producing strains (7 Enterobacter cloacae, 2 Klebsiella pneumoniae and 3 clonal Klebsiella oxytoca strains) detected among clinically relevant Enterobacteriaceae isolates from routine cultures at the Hospital del Mar (Barcelona, Spain) from December 2006 to May 2007. Methods: Susceptibility to carbapenems was evaluated with the MicroScan system. β-Lactamases were identified by PCR and sequencing. Clonal relationships between the isolates were analysed by PFGE. Transferability of the enzymes was tested by conjugation. Plasmid characterization was performed by PCR-based replicon typing and PFGE with S1 nuclease digestion of whole genomic DNA. The PFGE gels were then transferred and hybridized. Results: The disc diffusion method correctly identified five of the seven E. cloacae isolates as intermediate or resistant strains. All isolates produced the VIM-1 enzyme. Three E. cloacae and three K. oxytoca strains were also CTX-M-9-producing strains, and one E. cloacae was also a CTX-M-3-producing strain. The plasmids carrying the blaVIM gene, of unknown incompatibility group, had a size of ~75 kb (eight strains) or 40 kb (three strains) and also contained the qnrS and the aac(6')-Ib-cr genes. In the remaining strain the blaVIM-1 gene was found in an HI2 plasmid of 290 kb together with blaCTX-M-9, qnrA, qnrS and the aac(6́)-Ib-cr genes. Conclusions: The results showed a linkage between the blaVIM-1 and the qnrS and the aac(6')-Ib-cr genes, and between the blaCTX-M-9 and the qnrA genes. © The Author 2010.