Complete sequencing of an IncH plasmid carrying the bla ndm-1, bla ctx-m-15 and qnrB1 genes

Objectives: To characterize plasmid pNDM-MAR recovered from a Klebsiella pneumoniae isolate of sequence type (ST) 15 from Morocco, carrying the genes encoding the metallo-β-lactamase NDM-1, the extended-spectrum β-lactamase (ESBL) CTX-M-15 and the qnrB1 quinolone resistance determinant. Methods: The plasmid DNA sequence was obtained by using the 454-Genome Sequencer FLX procedure on a library constructed from total plasmid DNA obtained from an Escherichia coli J53 transconjugant. Contig assembly and predicted gaps were confirmed and filled by PCR-based gap closure. Results: Plasmid pNDM-MAR was 267 242 bp long and encoded 177 predicted proteins. It harboured novel replicons and transfer loci, defining a novel plasmid type within the IncH plasmid family. The bla NDM-1 gene was flanked by genetic elements that are distinct from those observed in other bla NDM-1-positive plasmids, including the groES and groEL chaperonin genes. This plasmid harboured the ESBL gene bla CTX-M-15 together with the quinolone resistance gene qnrB1. In addition, it harboured genes encoding resistance to tellurite, mercury, chloramphenicol and aminoglycosides. Interestingly, pNDM-MAR did not carry any 16S rRNA methylase gene, in contrast to other bla NDM-1-positive plasmids. Conclusions: This study underlines the diversity of genetic vehicles involved in the spread of the bla NDM-1 gene. Plasmid pNDM-MAR differed significantly from all known bla NDM-1-bearing plasmids. Comparative analysis of the pNDM-MAR sequence identified a novel type of IncH plasmid. © The Author 2012. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.