Genomic characterization of plasmid-borne colistin resistance variants, mcr-1.1 and mcr-1.26, in multidrug-resistant Escherichia coli isolated from backyard farm animals

Abstract

Colistin remains a high-priority, critically important antimicrobial that is used for treating severe infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, colistin resistance and the emergence of the mobile colistin resistance (mcr) genes have been increasingly documented in clinical and community settings, including in humans, animals, and the environment [ [1] , [2] , [3] ], which severely limits available antimicrobial options for addressing critical infections. Previous studies have reported that the wide dissemination of mcr-1 across Lebanon, an East Mediterranean country, is a major concern, especially in agricultural areas. Recently, we have identified a novel mcr variant, mcr-1.26, which appears to be spreading in Lebanon and is rarely reported abroad. This variant has been detected in hospitalised patients [ 4 ], otherwise healthy people [ 2 ], and birds [ 3 , 5 ] in Lebanon. Mcr-1.26–harbouring bacteria appear to concurrently exhibit resistance to other clinically and agriculturally important antimicrobials. Subsequently, we aimed to assess the faecal carriage and antimicrobial susceptibility patterns of colistin-resistant E. coli in backyard food animals in largely disenfranchised areas of North and South Lebanon.