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The complete sequence of the plasmid pNDM-1Dok01 carrying New Delhi metallo-β-lactamase (NDM-1) was determined by whole genome shotgun sequencing using Escherichia coli strain NDM-1Dok01 (multilocus sequence typing type: ST38) and the transconjugant E. coli DH10B. The plasmid is an IncA/C incompatibility type composed of 225 predicted coding sequences in 195. 5 kb and partially shares a sequence with bla (CMY-2) -positive IncA/C plasmids such as E. coli AR060302 pAR060302 (166. 5 kb) and Salmonella enterica serovar Newport pSN254 (176. 4 kb). The bla (NDM-1) gene in pNDM-1Dok01 is terminally flanked by two IS903 elements that are distinct from those of the other characterized NDM-1 plasmids, suggesting that the bla (NDM-1) gene has been broadly transposed, together with various mobile elements, as a cassette gene. The chaperonin groES and groEL genes were identified in the bla (NDM-1) -related composite transposon, and phylogenetic analysis and guanine-cytosine content (GC) percentage showed similarities to the homologs of plant pathogens such as Pseudoxanthomonas and Xanthomonas spp. , implying that plant pathogens are the potential source of the bla (NDM-1) gene. The complete sequence of pNDM-1Dok01 suggests that the bla (NDM-1) gene was acquired by a novel composite transposon on an extensively disseminated IncA/C plasmid and transferred to the E. coli ST38 isolate.
Sekizuka et al. (Fri,) studied this question.