title: Streptococcus tigurinus is highly virulent in a rat model of experimental endocarditis.
abstract: Streptococcus tigurinus is responsible for systemic infections in humans including infective endocarditis. We investigated whether the invasive trait of S. tigurinus in humans correlated with an increased ability to induce IE in rats. Rats with catheter-induced aortic vegetations were inoculated with 10⁴ CFU/ml of either of four S. tigurinus strains AZ_3a(T), AZ_4a, AZ_8 and AZ_14, isolated from patients with infective endocarditis or with the well known IE pathogen Streptococcus gordonii (Challis). Aortic infection was assessed after 24 h. S. tigurinus AZ_3a(T), AZ_4a and AZ_14 produced endocarditis in ≥80% of rats whereas S. gordonii produced endocarditis in only 33% of animals (P<0.05). S. tigurinus AZ_8 caused vegetation infection in 56% of the animals. The capacity of S. tigurinus to induce aortic infection was not related to their ability to bind extracellular matrix proteins (fibrinogen, fibronectin or collagen) or to trigger platelet aggregation. However, all S. tigurinus isolates showed an enhanced resistance to phagocytosis by macrophages and two of them had an increased ability to enter endothelial cells, key attributes of invasive streptococcal species.
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Tiago Rafael
authors.initials: TR
authors.lastname: Veloso
authors.forename: Andrea
authors.initials: A
authors.lastname: Zbinden
authors.forename: Federica
authors.initials: F
authors.lastname: Andreoni
authors.forename: Marlyse
authors.initials: M
authors.lastname: Giddey
authors.forename: Jacques
authors.initials: J
authors.lastname: Vouillamoz
authors.forename: Philippe
authors.initials: P
authors.lastname: Moreillon
authors.forename: Annelies Sophie
authors.initials: AS
authors.lastname: Zinkernagel
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Entenza
mesh_terms: D000818:Animals; D001011:Aorta / Q000382:microbiology / Q000473:pathology; D004195:Disease Models, Animal; D004697:Endocarditis, Bacterial / Q000382:microbiology* / Q000473:pathology*; D042783:Endothelial Cells / Q000382:microbiology; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D010587:Phagocytosis; D051381:Rats; D013290:Streptococcal Infections / Q000382:microbiology* / Q000473:pathology*; D013291:Streptococcus / Q000276:immunology / Q000472:pathogenicity*
keywords: Cell invasion; Experimental endocarditis; Phagocytosis; Platelet aggregation; Streptococcus tigurinus; Virulence