Recent outbreaks of shigellosis in California caused by two distinct populations of Shigella sonnei with either increased virulence or fluoroquinolone resistance

Varvara K. Kozyreva, Guillaume Jospin, Alexander L. Greninger, James P. Watt, Jonathan A Eisen, Vishnu Chaturvedi

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Shigella sonnei has caused unusually large outbreaks of shigellosis in California in 2014 and 2015. Preliminary data indicated the involvement of two distinct bacterial populations, one from San Diego and San Joaquin (SDi/SJo) and one from the San Francisco (SFr) Bay area. Whole-genome analysis and antibiotic susceptibility testing of 68 outbreak and archival isolates of S. sonnei were performed to investigate the microbiological factors related to these outbreaks. Both SDi/SJo and SFr populations, as well as almost all of the archival S. sonnei isolates belonged to sequence type 152 (ST152). Genome-wide single nucleotide polymorphism (SNP) analysis clustered the majority of California (CA) isolates to an earlier described lineage III. Isolates in the SDi/SJo population had a novel lambdoid bacteriophage carrying genes encoding Shiga toxin (STX) that were most closely related to that found in Escherichia coli O104:H4. However, the STX genes (stx1A and stx1B) from this novel phage had sequences most similar to the phages from Shigella flexneri and S. dysenteriae. The isolates in the SFr population were resistant to ciprofloxacin due to point mutations in gyrA and parC genes and were related to the fluoroquinoloneresistant S. sonnei clade within lineage III that originated in South Asia. The emergence of a highly virulent S. sonnei strain and introduction of a fluoroquinoloneresistant strain reflect the changing traits of this pathogen in California. An enhanced monitoring is advocated for early detection of future outbreaks caused by such strains.

Original languageEnglish (US)
Article numbere00344-16
JournalmSphere
Volume1
Issue number6
DOIs
StatePublished - Nov 1 2016

Keywords

  • California
  • Shigella sonnei
  • Shigellosis

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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