Characterization of the IncX3 Plasmid Producing From ST34.

Carbapenemase-producing has been a major clinical threat worldwide because therapeutic options are limited. Although New Delhi metallo-β-lactamase (NDM) is an important carbapenemase responsible for carbapenem resistance, it is uncommon in carbapenemase-producing in China. In this study, we described strain HZW25, an NDM-7-producing strain belonging to sequence type 34 (ST34). HZW25 exhibited resistance to all β-lactams tested but was susceptible to aminoglycosides and fluoroquinolones. The whole genome of HZW25 was sequenced with Pacific Biosciences RSII SMRT technology. HZW25 was composed of one chromosomal DNA and four plasmids, and the resistance genes of HZW25 were all located on the chromosome, except was located on a conjugative plasmid belonging to type IncX3 designated P4. The results of conjugation and transformation experiments showed that could be horizontally transferred successfully from the donor strain, HZW25, to the recipient strains, and α. The NDM variant transposable elements of the -harboring plasmid P4 were the and families. The upstream region of contained Δ, which was inserted near the or Δ sequence. Our study is the first report of metallo-β-lactamase NDM-7 in a carbapenemase-producing strain with ST34 in China. The emergence of NDM-producing would be troublesome during treatment using ceftazidime-avibactam. Therefore, the rapid and accurate identification of carbapenemase-producing is necessary.