Emergence of coexisting blaNDM and mcr-1 genes in Escherichia coli isolates from the guts of healthy individuals.

UNLABELLED: The emergence of blaNDM/mcr-1-positive Escherichia coli poses a huge challenge to infection control. The purpose of this study was to investigate the plasmid and genomic characteristics of blaNDM/mcr-1-positive E. coli isolates from the gut of healthy individuals. This study performed drug susceptibility testing, whole-genome sequencing (WGS), analysis of resistance genes, characterization of plasmids, and single-nucleotide polymorphism (SNP) analysis on blaNDM/mcr-1-positive E. coli isolates collected from the gut of 628 healthy individuals. Our results showed that all seven isolates were extensively drug-resistant, with susceptibility only to tigecycline and streptomycin. Notably, WGS revealed that blaNDM and mcr-1 were located on transferable plasmids, and SNP analysis placed the isolates in five distinct clades. These findings underscore the need for surveillance to monitor dissemination among healthy populations.

IMPORTANCE: This study reports isolation of Escherichia coli strains coharboring the critical resistance genes blaNDM (carbapenemase) and mcr-1 (colistin resistance) from the guts of healthy individuals (rural China). All seven isolates were extensively drug resistant, susceptible only to tigecycline and streptomycin. Crucially, both resistance genes were located on transferable plasmids, demonstrating potential for horizontal spread. Genomic analysis revealed diverse strains and plasmid types carrying these genes within mobile genetic contexts. This discovery identifies healthy human carriers as a significant reservoir for pan-resistant bacteria, posing severe public health challenges and necessitating urgent surveillance in endemic areas.