title: Characterization of DNase activity and gene in Streptococcus suis and evidence for a role as virulence factor.
abstract: BACKGROUND
  The Gram-positive bacterium Streptococcus suis serotype 2 is an important swine pathogen and emerging zoonotic agent. Multilocus sequence typing allowed dividing S. suis serotype 2 into sequence types (STs). The three major STs of S. suis serotype 2 from North America are 1 (most virulent), 25 (intermediate virulence) and 28 (less virulent). Although the presence of DNase activity in S. suis has been previously reported, little data is available. The aim of this study was to investigate DNase activity in S. suis according to STs, to characterize the activity and gene, and to provide evidence for a potential role in virulence.
  
  
  RESULTS
  We showed that ST1 and ST28 strains exhibited DNase activity that was absent in ST25 strains. The lack of activity in ST25 isolates was associated with a 14-bp deletion resulting in a shifted reading frame and a premature stop codon. The DNase of S. suis P1/7 (ST1) was cell-associated and active on linear DNA. A DNase-deficient mutant of S. suis P1/7 was found to be less virulent in an amoeba model. Stimulation of macrophages with the DNase mutant showed a decreased secretion of pro-inflammatory cytokines and matrix metalloproteinase-9 compared to the parental strain.
  
  
  CONCLUSIONS
  This study further expands our knowledge of S. suis DNase and its potential role in virulence.
authors.forename: Bruno
authors.initials: B
authors.lastname: Haas
authors.forename: Laetitia
authors.initials: L
authors.lastname: Bonifait
authors.forename: Katy
authors.initials: K
authors.lastname: Vaillancourt
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Charette
authors.forename: Marcelo
authors.initials: M
authors.lastname: Gottschalk
authors.affiliation: Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, 2420 Rue de la Terrasse, Quebec City, Quebec G1V 0A6, Canada. daniel.grenier@greb.ulaval.ca.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grenier
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D016207:Cytokines / Q000378:metabolism; D003851:Deoxyribonucleases / Q000235:genetics* / Q000378:metabolism; D004023:Dictyostelium / Q000382:microbiology; D004797:Enzyme-Linked Immunosorbent Assay; D005838:Genotype; D006801:Humans; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D009154:Mutation; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D012703:Serotyping; D013045:Species Specificity; D013290:Streptococcal Infections / Q000382:microbiology; D017011:Streptococcus suis / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D020298:U937 Cells; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines; D037521:Virulence Factors; D003851:Deoxyribonucleases; D020780:Matrix Metalloproteinase 9