Characterization of the genetic structure of mcr-1 gene among Escherichia coli isolates recovered from surface waters and sediments from Ecuador

Although anthropogenic activities contribute to the selection and spread of antibiotic resistance in aquatic environments, limited information is available from countries with absent or incomplete sewage treatment systems and the impact of their discharges onto water bodies. This study therefore aimed to characterize the genetic structure of colistin resistance (mcr) genes among Escherichia coli isolates recovered from surface waters and sediments in Ecuador. Out of 459 isolates, four Escherichia coli showed multidrug-resistant phenotypes, which harbored the mcr-1 gene and β-lactamases, such as blaTEM, blaCTX-M-15, blaCTX-M-55, or blaCTX-M-65 genes. Three E. coli isolates (U20, U30 and U144) shared a similar genetic environment surrounding the mcr-1 gene, which was located on plasmids. Only one E. coli isolate (U175) showed that the mcr-1 gene was chromosomally located. Moreover, the core genome multilocus sequence typing (cgMLST) analysis revealed that these isolates belong to different lineages. This study represents the first detection of the mcr-1 gene in multidrug-resistant E. coli isolates from environmental samples in Ecuador. [Display omitted] •First report of mcr-1 gene in E. coli from environmental samples in Ecuador•The isolates were obtained from irrigation channels used for agricultural purposes.•The lack of sewage treatment coverage could favor the spread of resistant bacteria.•cgMLST showed a great diversity among the evaluated isolates.