FbsA, a fibrinogen-binding protein from Streptococcus agalactiae, mediates platelet aggregation

Giampiero Pietrocola, Axel Schubert, Livia Visai, Mauro Torti, J. Ross Fitzgerald, Timothy J. Foster, Dieter J. Reinscheid, Pietro Speziale

Research output: Contribution to journalArticlepeer-review


The bacterium Streptococcus agalactiae is an etiologic agent in the pathogenesis of endocarditis in humans. FbsA, a fibrinogen-binding protein produced by this pathogen, is considered an important virulence factor. In the present study we provide evidence that S agalactiae clinical isolates bearing FbsA attach to fibri nogen and elicit a fibrinogen-dependent aggregation of platelets. Mutants of S agalactiae lacking the fbsA gene lost the ability to attach to fibrinogen and to aggregate platelets. Plasmid-mediated expression of fbsA restored the capability for fibrinogen binding and platelet aggregation in S agalactiae fbsA mutants, and allowed Lactococcus lactis to interact with fibrinogen and to aggregate human platelets. Moreover, a monoclonal anti-FbsA antibody inhibited bacterial adherence to fibrinogen and S agalactiae-induced platelet aggregation. Platelet aggregation was inhibited by aspirin, prostaglandin E1, the peptide RGDS, and the antibody abciximab, demonstrating the specificity of platelet aggregation by S agalactiae and indicating an involvement of integrin glycoprotein IIb/IIIa in the induction of platelet aggregation. Aggregation was also dependent on anti-FbsA IgG and could be inhibited by an antibody against the platelet FcγRIIA receptor. These findings indicate that FbsA is a crucial factor in S agalactiae-induced platelet aggregation and may therefore play an important role in S agalactiae-induced endocarditis.

Original languageEnglish
Pages (from-to)1052-1059
Number of pages8
Issue number3
Publication statusPublished - Feb 1 2005

ASJC Scopus subject areas

  • Hematology


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