Carbapenem-resistant and colistin-resistant Escherichia coli co-producing NDM-9 and MCR-1

Abstract

288 www.thelancet.com/infection Vol 16 March 2016 global public health concern, is that the antibiotic susceptibility results showed that the two K pneumoniae isolates were non-susceptible to nearly all antimicrobial drugs tested, including imipenem and meropenem (table). Additional PCR and sequencing analysis for the carbapenemase genes showed that the two K pneumoniae isolates carry the gene for NDM-5, a variant that has increased carba penemase activity by comparison with NDM-1. Carbapenem and colistin resistance were successfully trans ferred to E coli DH5α strains via electro poration individually, suggesting that the mcr-1 and blaNDM-5 genes are located on diff erent transferable plasmids. Complete sequencing of mcr-1-harbouring and blaNDM-5-harbouring plasmids, and whole genome sequencing, are underway. Our retrospective study documents that the mcr-1 gene has already established itself in highly drugresistant Enterobacteriaceae species, including its movement into carbapenem-resistant strains carrying an NDM-5 resistance plasmid. The coexistence of MCR-1 resistance and the NDM-5 approaches a pandrugresistant phenotype for which the use of colistin and the new β-lactam–βlactamase inhibitor, ceftazidime– avibactam, is ineffective. These findings stress the need to monitor the use of colistin in treatment of both human beings and animals, and the need for active surveillance to identify colistin resistance and for heightened infection control practices to restrict its further dissemination.