Abstract
Carbapenemase-producing Klebsiella pneumoniae 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 K. pneumoniae in China. In this study, we described strain HZW25, an NDM-7-producing K. pneumoniae 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 blaNDM–7 was located on a conjugative plasmid belonging to type IncX3 designated P4. The results of conjugation and transformation experiments showed that blaNDM–7 could be horizontally transferred successfully from the donor strain, HZW25, to the recipient strains, E. coli J53 and E. coli DH5α. The NDM variant transposable elements of the blaNDM–7-harboring plasmid P4 were the ISL3 and IS3000 families. The upstream region of blaNDM–7 contained ΔISAba125, which was inserted near the IS5 or ΔIS5 sequence. Our study is the first report of metallo-β-lactamase NDM-7 in a carbapenemase-producing K. pneumoniae strain with ST34 in China. The emergence of NDM-producing K. pneumoniae would be troublesome during treatment using ceftazidime-avibactam. Therefore, the rapid and accurate identification of carbapenemase-producing K. pneumoniae is necessary.
Highlights
Clinical treatment of carbapenem-resistant Enterobacteriaceae (CRE) is a critical challenge (Lee et al, 2016)
BlaNDM-7 was located on the plasmid, while the other resistance genes were located on the chromosome. blaNDM-7 was successfully transferred to E. coli AzR J53 by conjugation and to E. coli DH5α by electroporation, and the transconjugants displayed resistance to broad-spectrum cephalosporins and carbapenems (Table 1)
The presence of the blaNDM-7 gene in transconjugants was confirmed by PCR
Summary
Clinical treatment of carbapenem-resistant Enterobacteriaceae (CRE) is a critical challenge (Lee et al, 2016). New Delhi metallo-β-lactamase (NDM) is a metalloβ-lactamase able to hydrolyze carbapenem (Khan et al, 2017). NDM-producing CRE has increased globally recently, the worldwide distribution and prevalence of NDM-positive strains appear to be variable between different countries and regions NDM-producing CRE strains have mainly spread in South Asia, the Baltans, North Africa and the Middle East (Dortet et al, 2014; Wu et al, 2019). Chinese national surveillance of carbapenem-resistant CRE in China has shown that NDM-producing CRE are less common than KPCproducing CRE, and NDM-positive strains are mainly E. coli (Zhang et al, 2017, 2018; Wang et al, 2018)
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