Low level of polymyxin resistance among nonclonal mcr-1–positive Escherichia coli from human sources in Brazil

We report 26 human isolates of mcr-1–positive Escherichia coli, most of them (65.4%) with a polymyxin B MIC of 2 mg/L. Seventeen out of the 24 mcr-1–positive E. coli proved to be nonclonal by rep-PCR which strengthens the hypothesis of environmental or animal origin of these strains and reinforces the one health context of antimicrobial resistance. •The mcr-1 gene was detected in 26/368 (7.1%) Escherichia coli isolates from 19 patients.•None of the mcr-1–positive isolates were positive for blaKPC or blaNDM genes.•A total of 65.4% of mcr-1–positive isolates were susceptible to polymyxin B.•Most mcr-1–positive strains (18/26) exhibited a positive result for ESBL.•Molecular typing of 24/26 MCR-1–Escherichia coli indicated no clonal relation.