Occurrence of Highly Conjugative IncX3 Epidemic Plasmid Carrying blaNDM in Enterobacteriaceae Isolates in Geographically Widespread Areas

Abstract

The emergence of New Delhi metallo-β-lactamase (NDM) in common enterobacterial species is a major concern for healthcare. Early reports have revealed that the spread of NDM involved diverse and heterogeneous plasmids. Recently, the involvement of a rare, IncX3 subtype plasmid has been increasingly recognized. Here, we studied the prevalence of IncX plasmid subtypes in 198 carbapenem-resistant Enterobacteriaceae, originating from a territory-wide active surveillance in Hong Kong in 2016. The complete sequences and biological features of the blaNDM-carrying plasmids were investigated. A total of 62 NDM-type, 21 OXA-48 type, 14 IMP-type, 8 KPC-type, 4 IMI-type producers, and 89 non-carbapenemase-producers were tested for presence of IncX subtypes. IncX3 (n = 60) was the most common subtype, followed by IncX4 (n = 6) and IncX1 (n = 2). The prevalence of IncX3 subtype in isolates producing NDM, other carbapenemase types and non-carbapenemase producers were 75.8, 21.3, and 3.4%, respectively (P < 0.001). An IncX3 plasmid (size ∼50 kb) was confirmed to carry blaNDM in 47 isolates of different enterobacterial species. Thirteen IncX3 plasmids originating from six healthcare regions in Hong Kong were completely sequenced. The results showed that the IncX3 plasmids carrying blaNDM share a high degree of sequence identity with a previously reported plasmid, pNDM-HN380 (GenBank accession JX104760), over the backbone and genetic load regions. A blast search further revealed the occurrence of identical or nearly identical IncX3 plasmids carrying blaNDM in other part of China, Korea, Myanmar, India, Oman, Kuwait, Italy, and Canada. Two IncX3 carrying blaNDM were investigated further. Conjugation experiments demonstrated that the IncX3 plasmids could be efficiently transferred to multiple enterobacterial species at frequencies that are comparable or higher than the epidemic IncFII plasmid carrying blaCTX-M (pHK01). In addition, efficient transfer of the NDM plasmids occurred over a range of temperatures. In conclusion, this study demonstrated the important role played by IncX3 in the dissemination of NDM and the occurrence of pNDM-HN380-like plasmids in geographically widespread areas. The high mobility of IncX3 plasmid across different enterobacterial species highlights the ability of this plasmid replicon to be an important vehicle in worldwide dissemination of NDM.

Rapid Increase in Carbapenemase-Producing Enterobacteriaceae in Retail Meat Driven by the Spread of the bla NDM-5 -Carrying IncX3 Plasmid in China from 2016 to 2018

“…The ϳ50-kb plasmids carrying bla NDM were confirmed to be IncX3 type by using primers covering both the backbone of IncX3 plasmid and bla NDM genes. Totally, among the 110 NDM producers, 87 (79.1%) bla NDM genes were carried by IncX3 plasmids (Table S2), which was consistent with previous reports that the IncX3 plasmid was a major vector driving the transmission of bla NDM (7,12,13,18). IncX3 plasmid was first associated with the dissemination of bla NDM-1 among clinical CRE strains (19).…”

“…Most of the characterized STs were different from those of human sources in China. Yet, there were clones shared by isolates from humans and retail meat, such as E. coli ST10, ST167, ST410, ST641, ST744, and ST5229 and K. pneumoniae ST1, ST11, ST35, and ST45 (12)(13)(14). Conjugation and transformation experiments were performed on 52 NDM producers collected in 2016 to 2017.…”

“…Nowadays, it has disseminated in 23 countries, mostly in Asian countries, and was harbored by diverse Enterobacteriaceae species (see Fig. S5) (13). The wide distribution of bla NDM -carrying IncX3 plasmids might be explained by their ability to transfer among different bacterial species at a wide range of temperatures (30°C to 37°C) (13).…”

“…S5) (13). The wide distribution of bla NDM -carrying IncX3 plasmids might be explained by their ability to transfer among different bacterial species at a wide range of temperatures (30°C to 37°C) (13). However, further studies are needed to investigate the underlying mechanism and driving force.…”

<p>Emergence of Almost Identical F36:A-:B32 Plasmids Carrying <em>bla</em>_NDM-5 and <em>qepA</em> in <em>Escherichia coli </em>from Both Pakistan and Canada</p>

“…IncX3 has dominated the spread of bla NDM in many countries, particularly in Asian countries, such as China, 9 Korea, 20 Myanmar, 21 and India. 22 To the best of our knowledge, this study was the first to identify bla NDM -positive IncX3 plasmid in Pakistan. Similar to other reports, bla NDM-7 was embedded in an IS26bla NDM -ΔTn2 transposition unit which inserted into umuD gene in pHN4109c.…”