Occurrence and characterization of mcr-1-harbouring Escherichia coli isolated from pigs in Great Britain from 2013 to 2015

Nicholas A. Duggett, Ellie Sayers, Manal Abuoun, Richard J. Ellis, Javier Nunez-Garcia, Luke Randall, Robert Horton, Jon Rogers, Francesca Martelli, Richard P. Smith, Camilla Brena, Susanna Williamson, Miranda Kirchner, Robert Davies, Derrick Crook, Sarah Evans, Chris Teale, Muna F. Anjum

Research output: Contribution to journalArticlepeer-review


Objectives: To determine the occurrence of mcr-1-harbouring Escherichia coli in archived pig material originating in Great Britain (GB) from 2013 to 2015 and characterize mcr-1 plasmids.

Methods: Enrichment and selective culture of 387 archived porcine caecal contents and recovery from archive of 1109 E. coli isolates to identify colistin-resistant bacteria by testing for the presence of mcr-1 by PCR and RT–PCR. mcr-1-harbouring E. coli were characterized by WGS and compared with other available mcr-1 WGS.

Results: Using selective isolation following enrichment, the occurrence of mcr-1 E. coli in caeca from healthy pigs at slaughter from unique farms in GB was 0.6% (95% CI 0%–1.5%) in 2015. mcr-1 E. coli were also detected in isolates from two porcine veterinary diagnostic submissions in 2015. All isolates prior to 2015 were negative. WGS analysis of the four mcr-1-positive E. coli indicated no other antimicrobial resistance (AMR) genes were linked to mcr-1-plasmid-bearing contigs, despite all harbouring multiple AMR genes. The sequence similarity between mcr-1-plasmid-bearing contigs identified and those found in GB, Chinese and South African human isolates and Danish, French and Estonian livestock-associated isolates was 90%–99%.

Conclusions:mcr-1-harbouring plasmids were diverse, implying transposable elements are involved in mcr-1 transmission in GB. The low number of mcr-1-positive E. coli isolates identified suggested mcr-1 is currently uncommon in E. coli from pigs within GB. The high sequence similarity between mcr-1 plasmid draft genomes identified in pig E. coli and plasmids found in human and livestock-associated isolates globally requires further investigation to understand the full implications.
Original languageEnglish
Pages (from-to)691-695
JournalJournal of Antimicrobial Chemotherapy
Issue number3
Publication statusPublished - 15 Dec 2016


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