Genomic Characterization of mcr-1-Carrying E. coli Isolated from Food Handlers

The emergence of colistin-resistant Escherichai coli harboring the mcr-1 gene poses a significant public health concern, particularly due to colistin’s status as a last-resort antibiotic against multidrug-resistant Gram-negative infections. We provide the first identification of mcr-1-positive E. coli that was isolated from the hands of asymptomatic northern Thai restaurant employees. Twenty E. coli isolates were found from 150 hand swab samples; strain EC16 was shown to be colistin-resistant and to carry the mcr-1 gene. By hybrid-based complete genome sequencing, a 4.76 Mb chromosome and 2 plasmids (2 and 239 kb) were identified, the latter carrying multiple resistance genes including mcr-1. EC16 was shown to be clustered within ST1079 by core genome MLST and pangenome analysis, and it is closely connected to strains that are associated with humans and the environment. A varied resistome and virulome, comprising genes for adhesion and antibiotic inactivation, were revealed by LS-BSR analysis. pEcoEC16b was determined by plasmid typing to be an IncHI1A plasmid that is closely linked to p7PM1-IncHI1-mcr-1. Comparative study verified structural commonalities and shared resistance genes (mcr-1, tetA and cmlA1). These results underline the significance of One Health surveillance by demonstrating the potential of IncHI1A plasmids to spread multidrug resistance across species and environments. HIGHLIGHTS First report of mcr-1 positive E. coli isolated from the hands of restaurant workers New insights into potential human-associated reservoirs of colistin resistance. Our study highlights a new route of transmission via the hands of food handlers. GRAPHICAL ABSTRACT