Promoter variation and gene expression of mcr-1-harboring plasmids in clinical isolates of Escherichia coli and Klebsiella pneumoniae from a Chinese hospital

Next-generation sequencing of 6 mcr-1-harboring Escherichia coli and Klebsiella pneumoniae isolates collected from a tertiary care hospital in China revealed significant sequence variations in the regions flanking the mcr-1 gene. While sequence variations significantly affected the expression and promoter activity of mcr-1, the mcr-1 gene expression levels did not correlate with the in vitro colistin resistance levels, which warrants further in-depth investigations.