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

There is evidence to suggest that the virulence of Streptococcus strains in infective endocarditis might be due to the expression of binding sites for the extracellular matrix proteins of damaged valves. In this communication, we draw attention to one laminin-binding protein from a strain of Streptococcus gordonii isolated from a patient with human endocarditis. This 145-kDa protein was found on the cell wall of the bacterium. The level of expression of this binding protein might be regulated by the presence of extracellular matrix proteins: the protein was lacking after in vitro selection of laminin, collagen I, and fibronectin nonbinding variants, and it was recovered after growth of the variants when laminin or collagen I was added to the growth medium. It was also missing after 10 subcultures in minimal medium, indicating some positive control. Furthermore, the 145-kDa protein was recognized as a major antigen by sera from patients treated for streptococcal infective endocarditis, while sera from patients with valvulopathies gave only slight recognition, suggesting an increase of the expression of this protein during infective endocarditis. It was also shown that the 145-kDa protein carried a collagen I-like determinant detected with anti-human collagen I antibodies.
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PMID:Induction of a putative laminin-binding protein of Streptococcus gordonii in human infective endocarditis. 153 Sep 27

Human lactoferrin (HLf) is an iron-binding protein and a host-defence component at the mucosal surface. Recently, a specific receptor for HLf has been identified on a strain of Staphylococcus aureus associated with toxic shock syndrome. We have looked for the occurrence of 125I-HLf binding among 489 strains of S. aureus isolated from various clinical sources. HLf binding was common among S. aureus strains associated with furunculosis (94.3%), toxic shock syndrome (94.3%), endocarditis (83.3%) and septicaemia (82.8%) and other (nasal, vaginal or ocular) infections (96.1%) with a mean binding (in fmol) of 29.1, 21.9, 16.9, 22.2 and 29.2 respectively; the differences between mean HLf binding values of 29.1-29.2, 21.9-22.2 and 16.9 were significant. Furunculosis-associated (low-invasive or localised) isolates were high-to-moderate binders of HLf; 50% gave positive results at a threshold of greater than 31 fmol of 125I-HLf bound. In contrast, endocarditis-associated (high-invasive or systemic) isolates demonstrated low binding and did not bind 125I-HLf at the above threshold level. S. aureus recognised human or bovine Lf. However, bound 125I-HLf was more effectively inhibited in a dose-dependent manner by unlabelled bovine Lf than by homologous HLf. Binding of 125I-HLf to staphylococci was optimal with organisms grown in agar compared with those from broth cultures. The binding capacity of S. aureus was abolished when strains were grown on carbohydrate- and salt-rich agar media. HLf-binding ability of S. aureus did not correlate with fibronectin, fibrinogen, immunoglobulin G or laminin binding.
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PMID:Human lactoferrin binding in clinical isolates of Staphylococcus aureus. 205 16

Fibronectin is a large molecular weight protein that is found coating the surfaces of sites where endovascular damage has occurred. These are also the sites most commonly infected by bacteremic strains of staphylococci. Epidemiologic studies show a correlation between expression of fibronectin receptors and development of invasive infections. In vitro studies using cultured cells, artificial matrices containing fibronectin, blood clots, natural inflammatory matrices, and anti-fibronectin antibodies implicate fibronectin as an important ligand for staphylococcal attachment to host tissues and prosthetic devices. In the rat endocarditis model, S. aureus strains that lack the fibronectin receptor due to site-directed mutagenesis were unable to colonize the traumatized heart valves. These data suggest that the fibronectin receptor on staphylococci is important in the pathogenesis of endovascular infections. Because the fibronectin receptor is widely expressed on pathogenic of staphylococci, a broadly protective vaccine against S. aureus might be possible.
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PMID:Fibronectin-staphylococcal interactions in endovascular infections. 209 Jan 49

Inactivation of fibronectin (Fn) binding by insertional mutagenesis of Streptococcus sanguis with Tn916 reduces virulence of this bacterium in the rat model of infective endocarditis (IE). Transconjugants were screened for Fn adherence using an ELISA adherence test. One transconjugant had a decreased adherence to immobilized Fn. Southern hybridization demonstrated that the insertion occurred only once in this mutant. The parent strain and mutant strain JL113 were used as challenge strains in a rat endocarditis model. These experiments demonstrated that the mutant had a reduced ability (P less than 0.05) to produce IE. Spontaneous excision of Tn916 from JL113 produced strains identical to both the parental and mutant phenotypes. One strain (JLR-19) that retained the mutant phenotype and one (JLR-15) that regained the parental phenotype for Fn binding were tested for their ability to produce IE. These strains demonstrated that the ability to bind Fn and to produce IE were correlated after Tn916 excision. The reduced virulence of the mutant suggested that adherence of S. sanguis to immobilized Fn plays an important role in the production of IE.
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PMID:The role of fibronectin binding in the rat model of experimental endocarditis caused by Streptococcus sanguis. 216 50

Infective endocarditis caused by Staphylococcus aureus may be initiated by bacterial binding to cardiac valve cells. We investigated binding of whole S. aureus organisms to preparations of isolated porcine cardiac valve proteins. Cultured endothelial and subendothelial cells were surface labeled with iodine 125. After preabsorption with Escherichia coli, an organism that only rarely causes infective endocarditis, binding of surface proteins to S. aureus was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and subsequent autoradiography. The results showed that cardiac valve endothelial cells expressed a major S. aureus-binding protein with an approximate apparent molecular weight of 120,000. In contrast, cardiac valve subendothelial cells expressed on their surface a single species of binding protein with an approximate apparent molecular weight of 220,000; immunoblot analysis suggested that this protein was fibronectin. We also used radiolabeled S. aureus to probe cellular proteins transferred to nitrocellulose membranes. This technique identified a 125,000 molecular weight protein that bound S. aureus in endothelial cell extracts. We conclude that specific S. aureus binding to cardiac valve cells is mediated by different receptors for endothelial and subendothelial cells.
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PMID:Identification of Staphylococcus aureus binding proteins on isolated porcine cardiac valve cells. 229 65

Isogenic strains of Staphylococcus aureus, differing in fibronectin binding, were constructed for studies of the contribution of fibronectin binding to the in vivo pathogenesis of staphylococcal disease. Mutagenesis of S. aureus 879R4S was accomplished by mating with Enterococcus faecalis FA378 that carried the transposon Tn918. Four low-fibronectin-binding mutants were identified that bound 24- to 35-fold less fibronectin than the parent strain did. A spectinomycin-resistant strain, R4SSp, was transduced by a bacteriophage (80 alpha) lysate propagated on a low-binding mutant of 879R4S to produce R4SSp/1536, which bound less fibronectin, contained a single copy of the transposon, and grew on spectinomycin-containing medium. Using a rat model of endocarditis, we determined the distribution of S. aureus R4SSp and its transductant in normal and cardiac catheterized rats. Cultures of heart tissue showed that catheterized rats challenged with the fibronectin-binding parent strain had over 250-fold more organisms in the left heart than did rats challenged with the low-binding transductant. The ability to bind fibronectin had no effect on the number of S. aureus cells cultured from other tissues. These data suggest that the ability of S. aureus to bind fibronectin is an important factor in establishing adherence to damaged heart valves in vivo.
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PMID:Reduced adherence to traumatized rat heart valves by a low-fibronectin-binding mutant of Staphylococcus aureus. 254 22

Fibronectin binds to Staphylococcus aureus and may have a role in mediating its adherence to host tissue. Fibronectin was localized ultrastructurally on S. aureus in suspension and in interactions with cultured bovine endothelial cells. Probes were constructed by adsorbing fibronectin or its antibodies to colloidal gold beads (FN-Au or aFN-Au, respectively). Sites of fibronectin binding to S. aureus were demonstrated by reacting FN-Au with S. aureus in suspension. Transmission electron microscopy showed that FN-Au localized uniformly over the surface of S. aureus in suspension; most localized within 65 nm of the cell wall. The distribution of aFN-Au on S. aureus adherent to endothelial cells was concentrated in areas between S. aureus and endothelial cells. Areas of S. aureus not facing endothelial cells bound few aFN-Au. This suggests that the fibronectin labeled by aFN-Au in areas between S. aureus and endothelial cells was involved in adherence of the S. aureus, consistent with a role for fibronectin in endocarditis.
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PMID:Immunoelectron microscopic localization of fibronectin in adherence of Staphylococcus aureus to cultured bovine endothelial cells. 276 May 4

Fifteen bacterial isolates (12 streptococcal and 3 staphylococcal strains) from patients with bacterial endocarditis were screened for a variety of surface receptors, in an attempt to identify a common feature that might contribute to their ability to attach to and colonize damaged heart tissue. The bacterial receptors screened for, using a dot-blot autoradiographic procedure, included those for the Fc region of human IgG, fibrinogen, fibronectin and human C1q. Bacteria with receptors for each of the probes used could be identified, but no common receptor was present on all endocarditis-causing strains.
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PMID:Analysis of surface receptor expression on bacteria isolated from patients with endocarditis. 294 70

It is now generally accepted that adherence of microorganisms to various components of cardiac valve surfaces is an important early event in the pathogenesis of infective endocarditis. Several lines of evidence suggest that fibronectin may have a role in this adherence process. Fibronectin is an important component of the extracellular matrix of endothelium and fibroblasts and is exposed when these tissues are injured. Fibronectin binds to platelets and fibrin and thereby contributes to the thrombogenicity of surfaces. Because the structure of fibronectin consists of multiple functional domains, fibronectin can bind simultaneously and specifically to microorganisms and various tissue elements such as collagen and cells and may facilitate the uptake of microorganisms by endothelial cells and fibroblasts. Subinhibitory concentrations of certain antibiotics interfere with the expression of bacterial fibronectin receptors and inhibit the binding of Staphylococcus aureus to collagen matrices; this interaction may have implications for antibiotic prophylaxis of infective endocarditis.
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PMID:Role of fibronectin in infective endocarditis. 296 78

The adherence of Streptococcus sanguis to specific receptors exposed or deposited at the site of endothelial damage may play an important role in the development of infective endocarditis. Adherence of the Challis strain of S. sanguis to gelatin (or collagen) and gelatin-binding components of plasma was examined with an enzyme-linked immunosorbent assay. S. sanguis adhered poorly to immobilized gelatin and to molecular or fibrillar collagen. However, in the presence of fresh human plasma, the adherence of S. sanguis to all three substrates increased as much as eightfold. Removal of gelatin-binding proteins eliminates the ability of plasma to enhance adherence of S. sanguis to the substrates. Addition of purified human plasma fibronectin (Fn) to the absorbed plasma restored the adherence-promoting ability in a dose-dependent manner. A similar dose-dependent increase in S. sanguis adherence was observed when increasing concentrations of Fn alone were added to the gelatin-coated assay wells. S. sanguis adherence to immobilized fibronectin could not be inhibited by preincubating either the bacteria or the gelatin-coated assay wells with Fn or by including excess soluble Fn in the assay mixture. Studies with peptides purified from trypsin digests of Fn indicated that the 160- to 180-kilodalton (kDa) fragments which retain both the gelatin-binding and the cell-binding regions of the intact molecule support adherence of S. sanguis to gelatin. The 160- to 180-kDa fragments inhibited the interaction of S. sanguis with immobilized Fn. In contrast, intact Fn and the 31-kDa amino-terminal fragment were unable to inhibit the adherence when used in equivalent or greater molar amounts. These in vitro results suggest that in the presence of whole plasma, S. sanguis binds to immobilized gelatin or collagen via Fn bound to the immobilized substrates. Our finding that adherence of S. sanguis to immobilized Fn can occur in the presence of large concentrations of Fn, whether in plasma or purified, indicates that a S. sanguis-binding domain is cryptic in the Fn molecule while in solution and is exposed by a conformational change when the Fn becomes bound to gelatin-coated plastic. The ability of peptide fragments of Fn to inhibit S. sanguis adherence is consistent with this hypothesis.
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PMID:Adherence of Streptococcus sanguis to conformationally specific determinants in fibronectin. 297 Apr 35


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