Emergence of a novel hybrid mcr-1-bearing plasmid in an NDM-7-producing ST167 Escherichia coli strain of clinical origin

• Published in: Frontiers in microbiology 2022-08, Vol.13, p.950087-950087
• Main Authors: Xia, Shuang, Wang, Wei, Cheng, Jing, Zhang, Tingting, Xia, Ziwei, Zhao, Xiaoyu, Han, Yungang, Li, Yonghong, Shi, Xiufang, Qin, Shangshang
• Format: Article
• Language: English
• Subjects: cointegrate plasmid; Escherichia coli; Is26; mcr-1; Microbiology; ST167
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2022.950087

Colistin is considered as an antibiotic of ‘last resort’ for the treatment of lethal infections caused by carbapenem-resistant Enterobacterales (CRE), dissemination of plasmid-borne colistin resistance gene mcr-1 , particularly into CRE, resulting in the emergence of strains that approach pan-resistance. A wide variety of plasmid types have been reported for carrying mcr-1 . Among which, large IncHI2-type plasmids were multidrug-resistant (MDR) plasmids harbored multiple resistance determinants in addition to mcr-1 . Herein, we characterized a novel hybrid IncHI2-like mcr-1 -bearing plasmid in an NDM-7-producing ST167 Escherichia coli strain EC15-50 of clinical origin. Antimicrobial susceptibility testing showed E. coli EC15-50 exhibited an extensively drug-resistant (XDR) profile that only susceptible to amikacin and tigecycline. S1-PFGE, Southern hybridization and Whole-genome Sequencing (WGS) analysis identified a 46,161 bp bla NDM-7 -harboring IncX3 plasmid pEC50-NDM7 and a 350,179 bp mcr-1 -bearing IncHI2/HI2A/N/FII/FIA plasmid pEC15-MCR-50 in E. coli EC15-50. Sequence detail analysis revealed the type IV coupling protein (T4CP) gene was absent on pEC15-MCR-50, explaining that pEC15-MCR-50 was a non-conjugative plasmid. Comparative genetic analysis indicated the hybrid plasmid pEC15-MCR-50 was probably originated from pXGE1mcr-like IncHI2/HI2A/N plasmid and pSJ_94-like IncFII/FIA plasmid, and generated as a result of a replicative transposition process mediated by IS 26 . Currently, the prevalent mcr-1- carrying IncHI2 plasmids were rarely reported to be fused with other plasmids. The identification of the novel hybrid plasmid pEC15-MCR-50 in this study highlighted the importance of close surveillance for the emergence and dissemination of such fusion MDR plasmids, particularly in NDM-producing Enterobacterales .