Comparative genomic and phylogenetic analysis of a shiga toxin producing Shigella sonnei (STSS) strain

Domonkos Sváb, Balázs Bálint, Bálint Vásárhelyi, Gergely Maróti, I. Tóth

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Shigella strains are important agents of bacillary dysentery, and in recent years Shigella sonnei has emerged as the leading cause of shigellosis in industrialized and rapidly developing countries. More recently, several S. sonnei and Shigella flexneri strains producing Shiga toxin (Stx) have been reported from sporadic cases and from an outbreak in America. In the present study we aimed to shed light on the evolution of a recently identified Shiga toxin producing S. sonnei (STSS) isolated in Europe. Here we report the first completely assembled whole genome sequence of a multidrug resistant (MDR) Stx-producing S. sonnei (STSS) clinical strain and reveal its phylogenetic relations. STSS 75/02 proved to be resistant to ampicillin, streptomycin, tetracycline, chloramphenicol, thrimetoprim, and sulfomethoxazol. The genome of STSS 75/02 contains a 4,891,717 nt chromosome and seven plasmids including the 214 kb invasion plasmid (pInv) harboring type III secretion system genes and associated effectors. The chromosome harbors 23 prophage regions including the Stx1 converting prophage. The genome carries all virulence determinants necessary for an enteroinvasive lifestyle, as well as the Stx1 encoding gene cluster within an earlier described inducible converting prophage. In silico SNP genotyping of the assembled genome as well as 438 complete or draft S. sonnei genomes downloaded from NCBI GenBank revealed that S. sonnei 75/02 belongs to the more recently diverged global MDR lineage (IIIc). Targeted screening of 1131 next-generation sequencing projects taken from NCBI Short Read Archive of confirms that only a few S. sonnei isolates are Stx positive. Our results suggest that the acquisition of Stx phages could have occurred in different environments as independent events and that multiple horizontal transfers are responsible for the appearance of Stx phages in S. sonnei strains.

Original languageEnglish
Article number229
JournalFrontiers in cellular and infection microbiology
Volume7
Issue numberMAY
DOIs
Publication statusPublished - May 30 2017

Keywords

  • Genomics
  • Phylogeny
  • Plasmids
  • Prophages
  • Shiga toxigenic S. sonnei (STSS)
  • Shiga toxin (Stx)
  • Shigella sonnei
  • Whole genome

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Microbiology (medical)
  • Infectious Diseases

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