First Detection of the Plasmid-Mediated Colistin Resistance Gene, mcr-1, in Multidrug Resistant E. coli, in Backyard Animals in Lebanon

Abstract

The increase in antibiotic resistance has jeopardized the use of what is dubbed as last resort antibiotic, Polymyxin E. Specifically, the dissemination of mobile colistin resistance (mcr-1) gene has imperiled the effectiveness of this drug; posing a serious challenge worldwide. Previous studies documented the occurrence of the mobile colistin resistance gene, mcr-1, that encodes colistin (Polymyxin E) resistance in Escherichia coli isolated from vital matrices such as irrigation, sea water, aquaculture, drinking water and broiler chickens in Lebanon. To investigate the spread of mcr-1 gene to new matrices, we targeted backyard farms that have become a main food source for a large number of people in the country during the on-going economic crisis. In this study, 15 fecal samples were collected from a backyard farm in South Lebanon; 3 samples were collected from different animal species on the farm. All the samples were analyzed on agar media that was supplemented with 4 μg/ml colistin, and media without colistin to detect colistin and non- colistin resistant E. coli. Forty-five colonies were selected and purified from non-colistin plates, and twenty-seven colonies were selected and purified from colistin-containing plates. And all these colonies were selected for further analyses that included antimicrobial resistance phenotypes and gene-specific PCR analyses among others. All the colonies that grew on colistin plates were mcr-1 positive and were multidrug-resistant and the minimum inhibitory concertation of colistin varied between 4 and 1024 μg/ml. E. coli isolates (75%, 71%, and 44 %) carried blaTEM , isolated from chickens, pigeons and sheep respectively, and only 25% isolates of the chickens carried blaCTX-M. Plasmid transformation experiments and sequencing for mcr-1 gene were performed the transformants were colistin resistant and mcr-1 positive, indicating that the gene was plasmid-borne. Detecting mcr-1 positive E. coli and other resistant genes is a serious issue and can threaten the therapy of infectious diseases in the human and animal population. Our findings emphasize the absolute need to tackle the surge of colistin resistance in Lebanon through a One Health approach.