First environmental sample containing plasmid-mediated colistin-resistant ESBL-producing Escherichia coli detected in Norway.

We hereby report the detection of the plasmid borne mcr-1 gene conferring colistin resistance in an extended-spectrum β-lactamase (ESBL) producing Escherichia coli ST10 strain retrieved from seawater at a public beach in Norway. The sample was collected in September 2010 and was investigated by whole-genome sequencing in 2016. This report illustrates that E. coli strains carrying plasmid-mediated colistin resistance genes have also reached areas where this drug is hardly used at all. Surveillance of colistin resistance in environmental, veterinary, and human strains is warranted also in countries where colistin resistance is rare in clinical settings.