title: Molecular basis of virulence in Staphylococcus aureus mastitis.
abstract: BACKGROUND
  S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection.
  
  
  RESULTS
  We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that reproducibly induce severe (strain O11) and milder (strain O46) mastitis in ewes. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. A characteristic we observed in other S. aureus strains isolated from clinical mastitis cases.
  
  
  CONCLUSIONS
  Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity.
authors.affiliation: INRA, UMR1253, Science et Technologie du Lait et de l'Œuf, Rennes, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Le Maréchal
authors.forename: Nubia
authors.initials: N
authors.lastname: Seyffert
authors.forename: Julien
authors.initials: J
authors.lastname: Jardin
authors.forename: David
authors.initials: D
authors.lastname: Hernandez
authors.forename: Gwenaël
authors.initials: G
authors.lastname: Jan
authors.forename: Lucie
authors.initials: L
authors.lastname: Rault
authors.forename: Vasco
authors.initials: V
authors.lastname: Azevedo
authors.forename: Patrice
authors.initials: P
authors.lastname: François
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Maarten
authors.initials: M
authors.lastname: van de Guchte
authors.forename: Sergine
authors.initials: S
authors.lastname: Even
authors.forename: Nadia
authors.initials: N
authors.lastname: Berkova
authors.forename: Richard
authors.initials: R
authors.lastname: Thiéry
authors.forename: J Ross
authors.initials: JR
authors.lastname: Fitzgerald
authors.forename: Eric
authors.initials: E
authors.lastname: Vautor
authors.forename: Yves
authors.initials: Y
authors.lastname: Le Loir
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D008413:Mastitis / Q000382:microbiology*; D012756:Sheep; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins
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