Co-carrying of KPC-2, NDM-5, CTX-M-3 and CTX-M-65 in three plasmids with serotype O89: H10 Escherichia coli strain belonging to the ST2 clone in China.

Carbapenem-resistant Enterobacteriaceae strains as a new serious threat for the public health have been increasingly reported worldwide. In this study, one multi-resistant Escherichia coli strain ZSH6 which co-carried blaKPC-2, blaNDM-5 and blaCTX-M, was isolated from human blood sample. By using plasmid conjugation experiments, ZSH6 was found to harbor three plasmids carrying the blaNDM-5 gene, the blaKPC-2 and blaCTX-M gene, respectively. Whole-genome sequencing of ZSH6 yielded 122 scaffolds of chromosomal DNA and three circular plasmids including pZSH6-blaKPC-2 (46,319 bp), pZSH6-blaNDM-5 (46,161bp) and pZSH6-blaCTX-M (184,723). The isolate was classified to Sequence Type 2 and to the O89: H10 serotype. The results of genome analyses revealed that ZSH6 carried three virulence factors (capU, gad and iss) and twenty resistance genes [blaKPC-2blaNDM-5, blaCTX-M-3, blaCTX-M-65, blaTEM-1, floR, tet(A), tet(B), dfrA17, aadA5, sul1, mdf(A), mph(A), erm(B), aph(3')-Ia, aph(3')-Ib, aph(4)-Ia, aph(6)-Id, aac(3)-Iva, aac(3)-IId]. Therefore, the co-existence of such a large number of resistance genes in multiple plasmids making ZSH6 highly resistant to almost all kinds of commonly used antibiotics, and brings a serious challenge for resistance control and clinical treatment of infections caused by this bacterium.