Characterization of the IncX3 Plasmid Producing bla NDM-7 From Klebsiella pneumoniae ST34.

Carbapenemase-producingKlebsiella pneumoniaehas been a major clinical threat worldwide because therapeutic options are limited. Although New Delhi metallo-beta-lactamase (NDM) is an important carbapenemase responsible for carbapenem resistance, it is uncommon in carbapenemase-producingK. pneumoniaein China. In this study, we described strain HZW25, an NDM-7-producingK. pneumoniaestrain belonging to sequence type 34 (ST34). HZW25 exhibited resistance to all beta-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, exceptbla(NDM-7)was located on a conjugative plasmid belonging to type IncX3 designated P4. The results of conjugation and transformation experiments showed thatbla(NDM-7)could be horizontally transferred successfully from the donor strain, HZW25, to the recipient strains,E. coli J53andE. coli DH5 alpha. The NDM variant transposable elements of thebla(NDM-7)-harboring plasmid P4 were theISL3andIS3000families. The upstream region ofbla(NDM-7)contained Delta ISAba125, which was inserted near theIS5or Delta IS5sequence. Our study is the first report of metallo-beta-lactamase NDM-7 in a carbapenemase-producingK. pneumoniaestrain with ST34 in China. The emergence of NDM-producingK. pneumoniaewould be troublesome during treatment using ceftazidime-avibactam. Therefore, the rapid and accurate identification of carbapenemase-producingK. pneumoniaeis necessary.