Characterization of a pESI-like plasmid and analysis of multidrug-resistant Salmonella enterica infantis isolates in England and Wales

Winnie W.Y. Lee, Jennifer Mattock, David R. Greig, Gemma C. Langridge, David Baker, Samuel Bloomfield, Alison E. Mather, John R. Wain, Andrew M. Edwards, Hassan Hartman, Timothy J. Dallman, Marie A. Chattaway*, Satheesh Nair

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Salmonella enterica serovar Infantis is the fifth most common Salmonella serovar isolated in England and Wales. Epidemio-logical, genotyping and antimicrobial-resistance data for S. enterica Infantis isolates were used to analyse English and Welsh demographics over a 5 year period. Travel cases associated with S. enterica Infantis were mainly from Asia, followed by cases from Europe and North America. Since 2000, increasing numbers of S. enterica Infantis had multidrug resistance determinants harboured on a large plasmid termed ‘plasmid of emerging S. enterica Infantis’ (pESI). Between 2013 and 2018, 42 S. enterica Infantis isolates were isolated from humans and food that harboured resistance determinants to multiple antimicrobial classes present on a pESI-like plasmid, including extended-spectrum β-lactamases (ESBLs; blaCTX-M-65). Nanopore sequencing of an ESBL-producing human S. enterica Infantis isolate indicated the presence of two regions on an IncFIB pESI-like plasmid harbouring multiple resistance genes. Phylogenetic analysis of the English and Welsh S. enterica Infantis population indicated that the majority of multidrug-resistant isolates harbouring the pESI-like plasmid belonged to a single clade maintained within the population. The blaCTX-M-65 ESBL isolates first isolated in 2013 comprise a lineage within this clade, which was mainly associated with South America. Our data, therefore, show the emergence of a stable resistant clone that has been in circulation for some time in the human population in England and Wales, highlighting the necessity of monitoring resistance in this serovar.

Original languageEnglish
Article number000658
JournalMicrobial Genomics
Issue number10
Publication statusPublished - 2021

Bibliographical note

Funding Information:
A.E.M. acknowledges support from the National Institute for Health Research (NIHR) Imperial Biomedical Research Centre (BRC), and declares funding from Shionogi & Co., Ltd, for an unrelated project. The authors would like to thank Anaïs Painset in GBRU, PHE, for assisting in submitting sequence data to the NCBI Sequence Read Archive (SRA).

Funding Information:
T.J.D. and D.R.G. are affiliated to (and J.M. was supported by) the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Gastrointestinal Infections at the University of Liverpool in partnership with PHE, in collaboration with the University of Warwick, and are based at PHE. The views expressed are those of the author(s) and not necessarily those of the National Health Service (NHS), the NIHR, the Department of Health and Social Care nor PHE. G.C.L., A.E.M., J.R.W. and S.B. are supported by the Biotechnology and Biological Sciences Research Council (BBSRC) institute strategic programme Microbes in the Food Chain, BB/R012504/1, and its constituent project, BBS/E/F/000PR10348.

Publisher Copyright:
© 2021 The Authors.


  • Bla
  • ESBL
  • MDR
  • PESI and pESI-like plasmids
  • S. Infantis


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