title: Rapid evolution of virulence and drug resistance in the emerging zoonotic pathogen Streptococcus suis.
abstract: BACKGROUND
  Streptococcus suis is a zoonotic pathogen that infects pigs and can occasionally cause serious infections in humans. S. suis infections occur sporadically in human Europe and North America, but a recent major outbreak has been described in China with high levels of mortality. The mechanisms of S. suis pathogenesis in humans and pigs are poorly understood.
  
  
  RESULTS
  The sequencing of whole genomes of S. suis isolates provides opportunities to investigate the genetic basis of infection. Here we describe whole genome sequences of three S. suis strains from the same lineage: one from European pigs, and two from human cases from China and Vietnam. Comparative genomic analysis was used to investigate the variability of these strains. S. suis is phylogenetically distinct from other Streptococcus species for which genome sequences are currently available. Accordingly, approximately 40% of the approximately 2 Mb genome is unique in comparison to other Streptococcus species. Finer genomic comparisons within the species showed a high level of sequence conservation; virtually all of the genome is common to the S. suis strains. The only exceptions are three approximately 90 kb regions, present in the two isolates from humans, composed of integrative conjugative elements and transposons. Carried in these regions are coding sequences associated with drug resistance. In addition, small-scale sequence variation has generated pseudogenes in putative virulence and colonization factors.
  
  
  CONCLUSIONS
  The genomic inventories of genetically related S. suis strains, isolated from distinct hosts and diseases, exhibit high levels of conservation. However, the genomes provide evidence that horizontal gene transfer has contributed to the evolution of drug resistance.
authors: The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom. mh3@sanger.ac.uk
authors: Matthew T G
authors: MT
authors: Holden
authors: Heidi
authors: H
authors: Hauser
authors: Mandy
authors: M
authors: Sanders
authors: Thi Hoa
authors: TH
authors: Ngo
authors: Inna
authors: I
authors: Cherevach
authors: Ann
authors: A
authors: Cronin
authors: Ian
authors: I
authors: Goodhead
authors: Karen
authors: K
authors: Mungall
authors: Michael A
authors: MA
authors: Quail
authors: Claire
authors: C
authors: Price
authors: Ester
authors: E
authors: Rabbinowitsch
authors: Sarah
authors: S
authors: Sharp
authors: Nicholas J
authors: NJ
authors: Croucher
authors: Tran Bich
authors: TB
authors: Chieu
authors: Nguyen Thi Hoang
authors: NT
authors: Mai
authors: To Song
authors: TS
authors: Diep
authors: Nguyen Tran
authors: NT
authors: Chinh
authors: Michael
authors: M
authors: Kehoe
authors: James A
authors: JA
authors: Leigh
authors: Philip N
authors: PN
authors: Ward
authors: Christopher G
authors: CG
authors: Dowson
authors: Adrian M
authors: AM
authors: Whatmore
authors: Neil
authors: N
authors: Chanter
authors: Pernille
authors: P
authors: Iversen
authors: Marcelo
authors: M
authors: Gottschalk
authors: Josh D
authors: JD
authors: Slater
authors: Hilde E
authors: HE
authors: Smith
authors: Brian G
authors: BG
authors: Spratt
authors: Jianguo
authors: J
authors: Xu
authors: Changyun
authors: C
authors: Ye
authors: Stephen
authors: S
authors: Bentley
authors: Barclay G
authors: BG
authors: Barrell
authors: Constance
authors: C
authors: Schultsz
authors: Duncan J
authors: DJ
authors: Maskell
authors: Julian
authors: J
authors: Parkhill
mesh_terms: D000818:Animals; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial / Q000235:genetics*; D016680:Genome, Bacterial; D006801:Humans; D010802:Phylogeny; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology; D017011:Streptococcus suis / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics*; D015047:Zoonoses / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial