Emergence of an ST1326 (CG258) Multi-Drug Resistant Klebsiella pneumoniae Co-harboring mcr-8.2, ESBL Genes, and the Resistance-Nodulation-Division Efflux Pump Gene Cluster tmexCD1-toprJ1 in China
Congcong Liu, Yuchen Wu, Yinfei Fang, Zi Sang, Ling Huang, Ning Dong, Yu Zeng, Jiayue Lu, Rong Zhang, Gongxiang Chen
Abstract
CG258 is the dominant carbapenemase-producing Klebsiella pneumoniae clone worldwide and treatment of infections caused by this clone relies largely on the last-line antibiotics, colistin, and tigecycline. However, the emergence and global dissemination of mcr and tmexCD1 - toprJ1 genes have significantly compromised their clinical applications. CG258 K. pneumoniae carrying both mcr and tmexCD1 - toprJ1 have not been reported. A colistin-resistant strain T698-1 belonging to ST1326, a member of CG258, was isolated from the intestinal sample of a patient and characterized by the antimicrobial susceptibility testing, conjugation assay, WGS and bioinformatics analysis. It was resistant to colistin, tetracycline, aminoglycoside, fluoroqinolone, phenicols, sulfonamide, and some β-lactams, and positive for mcr-8.2 , tmexCD1 - toprJ1 , and ESBL genes ( bla DHA– 1 and bla CTX–M– 15 ). The tmexCD1 - toprJ1 gene cluster was located in an multi-drug resistant (MDR) region flanked by Tn As1 elements on an IncHI1B/FIB plasmid. The genetic context of tmexCD1 - toprJ1 was slightly distinct from previously reported Tn 5393 -like structures, with an IS 26 element disrupting the upstream Tn 5393 and its adjacent genetic elements. The mcr-8.2 gene was inserted into the backbone of an IncFII/FIA plasmid with the genetic context of IS Ecl1 - mcr-8.2 - orf -IS Kpn26 . To our knowledge, this is the first report of co-occurrence of mcr-8.2 and tmexCD1 - toprJ1 in a CG258 K. pneumoniae strain. Though this strain is tigecycline sensitive, the acquisition of colistin and tigecycline resistance determinants by the endemic CG258 K. pneumoniae clone still poses a serious public health concern. CG258, which became resistant to multiple last resort antibiotics, would be the next emerging superbug.