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Query: UMLS:C0014118 (endocarditis)
 15,629 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of certain strains of Streptococcus sanguis to aggregate human platelets in vitro may be related to their virulence in the pathogenesis of infective endocarditis. We have studied the mechanisms of aggregation of human platelets by S. sanguis strain NCTC 7863. Platelet aggregation follows incubation of S. sanguis cells with platelet-rich plasma from normal, healthy adults, after a lag of 7-19 min. Platelet aggregation was accompanied by 5-hydroxytryptamine release and thromboxane B2 production. Aggregation was prevented by aspirin and by EDTA. Platelets from two patients with Glanzmann's thrombasthenia did not respond to bacteria. Fixed, washed platelets resuspended in normal plasma were not agglutinated by S. sanguis. Blocking the glycoprotein Ib receptor with a monoclonal antibody inhibited aggregation of PRP. However, S. sanguis did not induce von Willebrand factor (vWF) binding to platelets; nor did the bacteria prevent ristocetin-induced platelet agglutination or vWF binding. The aggregation response was not related to plasma vWF activity levels in normal subjects or in patients with von Willebrand's disease. The platelet response to S. sanguis therefore resembles true aggregation, requiring the cyclo-oxygenase pathway and the presence of glycoprotein IIb/IIIa. The mechanism also involves glycoprotein Ib, but not apparently through irreversible binding of vWF.
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PMID:Mechanisms of platelet aggregation by Streptococcus sanguis, a causative organism in infective endocarditis. 833 84

Immunological complications of staphylococcal endocarditis are rare but represent a serious event in this condition. The authors report the case of acute tricuspid valve endocarditis in a 38 year old drug addict. The diagnosis was suggested by the presentation of bilateral bacterial lung abscesses with a murmur of tricuspid regurgitation, and confirmed by transthoracic and transoesophageal echocardiography. Bacteriological cultures isolated a methicillin-sensitive staphylococcal aureus. The outcome was complicated by a nephrotic syndrome associated with a glomerulonephritis by deposition of immune complexes and an autoimmune thrombocytopaenic purpura due to acquired anti-glycoprotein IIb IIIa antibodies. Antibiotic therapy led to cure without sequellae of the endocarditis, the nephrotic syndrome and the thrombocytopaenia. This case illustrates the risk of immunological complications during acute staphylococcal tricuspid valve endocarditis and also illustrates the possibility of a favourable outcome with antibiotic therapy alone. However, the potential severity of these complications indicates the need for early diagnosis and strict surveillance of this condition.
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PMID:[Systemic manifestations and development of GPIIbIIIa antibodies in the course of staphylococcal endocarditis. Report of a case]. 1022 Nov 48

The direct binding of bacteria to platelets may be an important virulence mechanism in the pathogenesis of infective endocarditis. We have previously described Staphylococcus aureus strain PS12, a Tn551-derived mutant of strain ISP479, with reduced ability to bind human platelets in vitro. When tested in an animal model of endocarditis, the PS12 strain was less virulent than its parental strain, as measured by bacterial densities in endocardial vegetations and incidence of systemic embolization. We have now characterized the gene disrupted in PS12 and its function in platelet binding. DNA sequencing, Southern blotting, and PCR analysis indicate that PS12 contained two Tn551 insertions within the clumping factor A (ClfA) locus (clfA). The first copy was upstream from the clfA start codon and appeared to have no effect on ClfA production. The second insertion was within the region encoding the serine aspartate repeat of ClfA and resulted in the production of a truncated ClfA protein that was secreted from the cell. A purified, recombinant form of the ClfA A region, encompassing amino acids 40 through 559, significantly reduced the binding of ISP479C to human platelets by 44% (P = 0.0001). Immunoprecipitation of recombinant ClfA that had been incubated with solubilized platelet membranes coprecipitated a 118-kDa platelet membrane protein. This protein does not appear to be glycoprotein IIb. These results indicate that platelet binding by S. aureus is mediated in part by the direct binding of ClfA to a novel 118-kDa platelet membrane receptor.
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PMID:Clumping factor A mediates binding of Staphylococcus aureus to human platelets. 1129 31

Numerous studies have implicated bacteria in cardiovascular disease, but there is a paucity of information on the mechanism involved. In this study we show how the common oral bacterium Streptococcus sanguis can directly interact with platelets, resulting in activation and aggregate formation. Platelet aggregation was dependent on glycoprotein IIb/IIIa (GPIIb/IIIa) and thromboxane. Platelets could also directly bind to S sanguis, but this interaction was not inhibited by GPIIb/IIIa antagonists. Antibodies to GPIb could inhibit both platelet aggregation and platelet adhesion to bacteria. This suggested a direct interaction between GPIb and S sanguis; however, this interaction did not require von Willebrand factor, the normal ligand for GPIb. By use of a range of monoclonal antibodies to GPIb and the enzyme mocharagin, which cleaves GPIb at amino acid 282, the interaction was localized to a region within the N-terminal 1-225 portion of GPIbalpha. Furthermore S sanguis failed to induce aggregation of platelets from a patient with Bernard-Soulier disease, the organism bound to Chinese hamster ovary cells transfected with the GPIbalpha gene but did not bind to mock-transfected cells and biotin-labeled S sanguis cells bound to purified GPIb in ligand blots. It is suggested that the interaction between S sanguis and GPIb is important in the pathogenesis of infective endocarditis and may also play a contributory role in some cases of myocardial infarction.
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PMID:A role for glycoprotein Ib in Streptococcus sanguis-induced platelet aggregation. 1209 42

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 fibrinogen 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 E(1,) 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 FcgammaRIIA 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.
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PMID:FbsA, a fibrinogen-binding protein from Streptococcus agalactiae, mediates platelet aggregation. 1538 64

Aggregation of human platelets by Streptococcus gordonii DL1, an interaction implicated in the pathogenesis of infective endocarditis, requires the expression of hsa, the gene encoding the sialic acid-binding adhesin (Hsa) of this organism. To identify the sialoglycoproteins on the platelet surface as the receptors for Hsa, intrinsic membrane proteins were assessed by bacterial overlay assay. S. gordonii DL1 adhered to 130-140-kDa proteins, a reaction that was abolished by neuraminidase treatment of immobilized platelet surface proteins. These sialoglycoproteins were identified as platelet glycoprotein Ib alpha (GPIbalpha ) and glycoprotein IIb (GPIIb) by immunoprecipitation with specific monoclonal antibody against each glycoprotein.
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PMID:Identification of platelet receptors for the Streptococcus gordonii DL1 sialic acid-binding adhesin. 1611 9