Nationwide Surveillance of Clinical Carbapenem-resistant Enterobacteriaceae (CRE) Strains in China

The increasing incidence of carbapenem-resistant Enterobacteriaceae (CRE) - mediated hospital infections in China prompted a need to investigate the genetic basis of emergence of such strains. A nationwide survey was conducted in China covering a total of 1105 CRE strains collected from 25 geographical locales with results showing that acquisition of two carbapenemase genes, blaKPC-2 and blaNDM, was responsible for phenotypic resistance in 90% of the CRE strains tested (58% and 32% respectively), among which several major strain types, such as ST11 of K. pneumoniae and ST131/ST167 of E. coli, were identified, suggesting that dissemination of specific resistant clones is mainly responsible for emergence of new CRE strains. Prevalence of the fosA3 gene which mediates fosfomycin resistance, was high, while the colistin resistance determinant mcr-1 was rarely present in these isolates. Consistently, the majority of the blaNDM-bearing plasmids recoverable from the test strains belonged to IncX3, which contained a common core structure, blaNDM-blaMBL-trpF. Likewise, the core structure of ISKpn27-blaKPC-2-ISKpn2 was observed among plasmids harboring the blaKPC-2 gene, although they were genetically more divergent. In conclusion, the increasing prevalence of CRE strains in China is attributed to dissemination of conservative mobile elements carrying blaNDM or blaKPC-2 on conjugative and non-conjugative plasmids. •Over 90% of CRE strains in China harbored the blaNDM or blaKPC-2 gene.•The predominant types of carbapenem-resistant K. pneumoniae and E. coli were ST11 and ST131/ST167 respectively.•Conservative mobile elements carrying blaNDM and blaKPC-2 contributed to transmission of carbapenemase genes in CRE. Large scale surveillance of CRE was rarely reported worldwide except for a recent survey reported in European countries. A nationwide survey was conducted in this study to depict the epidemiological features of CRE strains in China and the types of resistance elements that they harbored. We showed that the increasing prevalence of CRE strains in China was due to dissemination of major resistant clones that harbor several major types of blaNDM or blaKPC-2 – bearing conjugative plasmids, and that infections caused by such strains remain treatable by various non-β-lactam antibiotics, including colistin.