Effect of thrombocytopenia on the early course of streptococcal endocarditis

J Infect Dis. 1993 Oct;168(4):910-4. doi: 10.1093/infdis/168.4.910.


Although platelets are a major factor in the pathogenesis of endocarditis, it is unclear if these cells promote or limit disease progression. To address this issue, the effects of thrombocytopenia on the early course of endovascular infection were examined. Aortic valve endocarditis was produced in rabbits by using Streptococcus sanguis M99. Thrombocytopenia was induced by intravenous administration of antiplatelet serum. Compared with controls (infected rabbits given nonimmune serum), thrombocytopenic rabbits had higher densities of streptococci within vegetations (mean log10 cfu/g, 9.78 vs. 8.11, P < .002) and a higher total number of bacteria per valve (mean log10 total cfu/valve, 8.96 vs. 7.43, P < .004). When tested for its interactions with platelets in vitro, strain M99 bound, activated, and aggregated rabbit platelets extensively and was rapidly killed by platelet microbicidal protein. These results indicate that platelets can limit disease progression in endocarditis. The host defense properties of platelets may in part be mediated by platelet microbicidal protein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Adhesion
  • Blood Platelets / drug effects
  • Blood Platelets / microbiology
  • Blood Platelets / physiology*
  • Blood Proteins / biosynthesis
  • Blood Proteins / isolation & purification
  • Blood Proteins / pharmacology
  • Chemokines*
  • Endocarditis, Bacterial / blood
  • Endocarditis, Bacterial / complications*
  • Humans
  • Platelet Aggregation*
  • Rabbits
  • Streptococcal Infections / blood
  • Streptococcal Infections / complications*
  • Streptococcus sanguis / drug effects
  • Streptococcus sanguis / isolation & purification*
  • Streptococcus sanguis / physiology
  • Thrombin / pharmacology
  • Thrombocytopenia / complications*
  • beta-Thromboglobulin


  • Blood Proteins
  • Chemokines
  • PPBP protein, human
  • beta-Thromboglobulin
  • platelet microbicidal protein, Oryctolagus cuniculus
  • Thrombin