Contribution of cell surface protein antigen c of Streptococcus mutans to platelet aggregation.
BACKGROUND
Streptococcus mutans is considered to be one of the pathogens that cause infective endocarditis. The purpose of the present study was to examine the properties of S. mutans with regard to platelet aggregation by focusing on its high molecular protein antigen c (PAc).


METHODS
The platelet aggregation properties of six clinical strains and one isogenic mutant strain of S. mutans were analysed using an aggregometer and confocal microscopy, as well as with an inhibition assay of platelet aggregation using anti-PAc serum.


RESULTS
S. mutans strains with PAc expression induced platelet aggregation, while a PAc-deficient mutant and two clinical isolates with no PAc expression did not. When platelets were pretreated with higher amounts of anti-PAc serum, the platelet aggregation rate was reduced in a dose-dependent manner, indicating that PAc binds directly to platelets.


CONCLUSIONS
S. mutans PAc is involved in human platelet aggregation and may be one of the virulence factors in the pathogenesis of infective endocarditis.
Matsumoto-Nakano
M
M
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Osaka, Japan.
Tsuji
M
M
Inagaki
S
S
Fujita
K
K
Nagayama
K
K
Nomura
R
R
Ooshima
T
T
D000907:Antibodies, Bacterial / Q000502:physiology; D000942:Antigens, Bacterial / Q000235:genetics / Q000502:physiology*; D000954:Antigens, Surface / Q000235:genetics / Q000502:physiology*; D016470:Bacteremia / Q000382:microbiology; D001422:Bacterial Adhesion / Q000276:immunology; D004697:Endocarditis, Bacterial / Q000382:microbiology; D006801:Humans; D007106:Immune Sera; D018613:Microscopy, Confocal; D009154:Mutation / Q000235:genetics; D010974:Platelet Aggregation / Q000276:immunology*; D013290:Streptococcal Infections / Q000382:microbiology; D013295:Streptococcus mutans / Q000235:genetics / Q000276:immunology*; D014774:Virulence
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D007106:Immune Sera