Acquisition and loss of ctx-m plasmids in shigella species associated with msm transmission in the uk

Rebecca K. Locke, David R. Greig, Claire Jenkins, Tim J. Dallman, Lauren A. Cowley

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12 Citations (SciVal)


Shigellosis in men who have sex with men (MSM) is caused by multidrug resistant Shigellae, exhibiting resistance to anti-microbials including azithromycin, ciprofloxacin and more recently the third-generation cephalosporins. We sequenced four blaCTX-M-27-positive MSM Shigella isolates (2018–20) using Oxford Nanopore Technologies; three S. sonnei (identified as two MSM clade 2, one MSM clade 5) and one S. flexneri 3a, to explore AMR context. All S. sonnei isolates harboured Tn7/ Int2 chromosomal integrons, whereas S. flexneri 3a contained the Shigella Resistance Locus. All strains harboured IncFII pKSR100-like plasmids (67-83kbp); where present blaCTX-M-27 was located on these plasmids flanked by IS26 and IS903B, however blaCTX-M-27 was lost in S. flexneri 3a during storage between Illumina and Nanopore sequencing. IncFII AMR regions were mosaic and likely reorganised by IS26; three of the four plasmids contained azithromycin-resistance genes erm(B) and mph(A) and one harboured the pKSR100 integron. Additionally, all S. sonnei isolates possessed a large IncB/O/K/Z plasmid, two of which carried aph(3’)-Ib/aph(6)-Id/sul2 and tet(A). Monitoring the transmission of mobile genetic elements with co-located AMR determinants is necessary to inform empirical treatment guidance and clinical management of MSM-associated shigellosis.

Original languageEnglish
Article number000644
JournalMicrobial Genomics
Issue number8
Early online date24 Aug 2021
Publication statusPublished - 31 Aug 2021


  • Antimicrobial resistance
  • CTX-M
  • ESBL
  • MSM
  • Public health
  • Shigella

ASJC Scopus subject areas

  • Epidemiology
  • Microbiology
  • Molecular Biology
  • Genetics


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