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J Antimicrob Chemother. 2014 Oct;69(10):2658-68. doi: 10.1093/jac/dku206. Epub 2014 Jun 11.

Nucleotide sequences of 16 transmissible plasmids identified in nine multidrug-resistant Escherichia coli isolates expressing an ESBL phenotype isolated from food-producing animals and healthy humans.

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UCD Centre for Food Safety, School of Public Health, Physiotherapy & Population Science, University College Dublin, Belfield, Dublin 4, Ireland.
Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 272, CH-8057 Zurich, Switzerland.
UCD Centre for Food Safety, School of Public Health, Physiotherapy & Population Science, University College Dublin, Belfield, Dublin 4, Ireland Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Stranmillis Road, Belfast BT9 5AG, Northern Ireland



Nine extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolated from healthy humans and food-producing animals were found to transfer their cefotaxime resistance marker at high frequency in laboratory conjugation experiments. The objective of this study was to completely characterize 16 transmissible plasmids that were detected in these bacterial isolates.


The nucleotide sequences of all 16 plasmids were determined from transconjugants using next-generation sequencing technology. Open reading frames were assigned using Rapid Annotation using Subsystem Technology and analysed by BLASTn and BLASTp. The standard method was used for plasmid multilocus sequence typing (pMLST) analysis. Plasmid structures were subsequently confirmed by PCR amplification of selected regions.


The complete circularized nucleotide sequence of 14 plasmids was determined, along with that of a further two plasmids that could not be confirmed as closed. These ranged in size from 1.8 to 166.6 kb. Incompatibility groups and pMLSTs identified included IncI1/ST3, IncI1/ST36, IncN/ST1, IncF and IncB/O, and those of the same Inc types presented a similar backbone structure despite being isolated from different sources. Eight plasmids contained bla(CTX-M-1) genes that were associated with either ISEcp1 or IS26 insertion sequence elements. Six plasmids isolated from humans and chickens were identical or closely related to the IncI1 reference plasmid, R64.


These data, based on comparative sequence analysis, highlight the successful spread of blaESBL-harbouring plasmids of different Inc types among isolates of human and food-producing animal origin and provide further evidence for potential dissemination routes.


CTX-M; IncI1; TEM; conjugation; resistance genes

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