title: Hyaluronate lyase activity of Streptococcus suis serotype 2 and modulatory effects of hyaluronic acid on the bacterium's virulence properties.
abstract: BACKGROUND
  Streptococcus suis serotype 2 is a major swine pathogen and zoonotic agent worldwide causing mainly meningitis and septicemia. Hyaluronate lyases are enzymes that degrade hyaluronic acid, a major constituent of animal tissues, and have been reported as virulence factors in various bacterial species. Since the hyaluronate lyase of S. suis has been considered ambiguously as a virulence factor, we screened 50 isolates from the three major clonal complexes found in North America (sequence type [ST] 1, ST25, and ST28) known to differ in their degree of virulence in order to link the presence or absence of this activity with the degree of virulence. Moreover, the effect of exogenous hyaluronic acid on S. suis virulence factor gene expression and the pro-inflammatory response of brain macrovascular endothelial cells (BMEC) was also investigated.
  
  
  RESULTS
  We found that all but one ST1 isolates (high virulence) were devoid of hyaluronate lyase activity whereas all ST25 (intermediate virulence) and ST28 (low virulence) isolates possessed the activity. A 2 bp insertion was responsible for the lack of activity in ST1 strains. Since the most virulent isolates did not degrade hyaluronic acid, this tissue component may be found during the infectious process. Therefore, we investigated its effect on S. suis and host cells. Hyaluronic acid was found to modulate S. suis adhesion to BMEC, to increase S. suis virulence factor expression, and to enhance pro-inflammatory cytokine secretion by BMEC.
  
  
  CONCLUSIONS
  These findings suggest that S. suis hyaluronate lyase does not represent a critical virulence factor in its active form. However, exogenous hyaluronic acid that is likely to interact with S. suis and host cells during the course of infection appears to modulate several virulence determinants of the bacterium, in addition to promote inflammation.
authors.affiliation: Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, 2420 Rue de la Terrasse, Quebec City, QC, G1V 0A6, Canada. bruno.haas.1@ulaval.ca.
authors.forename: Bruno
authors.initials: B
authors.lastname: Haas
authors.affiliation: Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, 2420 Rue de la Terrasse, Quebec City, QC, G1V 0A6, Canada. katy.vaillancourt@greb.ulaval.ca.
authors.forename: Katy
authors.initials: K
authors.lastname: Vaillancourt
authors.affiliation: Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, 2420 Rue de la Terrasse, Quebec City, QC, G1V 0A6, Canada. laetitia.bonifait@criucpq.ulaval.ca.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Bonifait
authors.affiliation: Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Fonds de Recherche du Québec-Nature et Technologies (FRQNT), Saint-Hyacinthe, QC, Canada. marcelo.gottschalk@umontreal.ca.|Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, QC, Canada. marcelo.gottschalk@umontreal.ca.
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, QC, G1V 0A6, Canada. daniel.grenier@greb.ulaval.ca.|Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Fonds de Recherche du Québec-Nature et Technologies (FRQNT), Saint-Hyacinthe, QC, Canada. daniel.grenier@greb.ulaval.ca.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grenier
mesh_terms: D001422:Bacterial Adhesion; D001483:Base Sequence; D018441:Biofilms; D005798:Genes, Bacterial; D006820:Hyaluronic Acid / Q000494:pharmacology*; D008969:Molecular Sequence Data; D011133:Polysaccharide-Lyases / Q000235:genetics / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D017011:Streptococcus suis / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity; D014774:Virulence / Q000187:drug effects* / Q000235:genetics
chemical_list: D006820:Hyaluronic Acid; D011133:Polysaccharide-Lyases; C100002:hyaluronate lyase