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Microbial adhesion to fibronectin in vitro correlates with production of endocarditis in rabbits
Abstract:
Microbial adhesion to the constituents of nonbacterial thrombotic endocarditis (NBTE) is an important early event in the pathogenesis of infective endocarditis. Fibronectin is a ubiquitous mammalian glycoprotein with diverse functions which binds to certain bacteria but not to others. In this study, we determined that fibronectin is present on the surface of NBTE (after catheter-induced aortic valve trauma) but not on normal rabbit cardiac valvular endothelium. The adhesion of various bacteria and yeasts to human fibronectin in tissue culture wells was then measured. Microorganisms with a high isolation frequency from endocarditis cases (Staphylococcus aureus, Candida tropicalis, C. albicans, Streptococcus faecalis, S. sanguis) bound significantly better (P less than 0.01) to fibronectin in vitro than other organisms (Escherichia coli, C. krusei, Pseudomonas aeruginosa) rarely implicated in this disease. Microbial adhesion to fibronectin correlated closely with the propensity of each organism to produce endocarditis in rabbits (e.g., ID50) with preexistent NBTE. A similar distribution was noted after binding of soluble radiolabeled fibronectin to bacteria in suspension. The results suggest that fibronectin, expressed on the surface of NBTE, may mediate microbial adhesion of circulating organisms to initiate colonization during the early pathogenesis of infective endocarditis.
Insights
Fibronectin on nonbacterial thrombotic endocarditis (NBTE) surfaces promotes adhesion of disease-causing microbes. This binding mechanism is crucial for initiating infective endocarditis, particularly in rabbits with NBTE.
Area of Science:
- Microbiology
- Pathogenesis
- Biochemistry
Background:
- Microbial adhesion to nonbacterial thrombotic endocarditis (NBTE) is a key step in infective endocarditis development.
- Fibronectin, a mammalian glycoprotein, binds to specific bacteria but not all.
- Understanding fibronectin's role in microbial adhesion is vital for studying endocarditis.
Purpose of the Study:
- To investigate the presence of fibronectin on NBTE.
- To quantify the adhesion of various microorganisms to fibronectin.
- To correlate microbial adhesion to fibronectin with endocarditis-causing potential.
Main Methods:
- NBTE was induced in rabbits via catheter-induced aortic valve trauma.
- Fibronectin presence on normal and NBTE-affected valves was assessed.
- Microbial adhesion assays were performed using fibronectin in tissue culture wells.
- Radiolabeled fibronectin binding to bacteria in suspension was measured.
Main Results:
- Fibronectin was detected on NBTE surfaces but not on normal cardiac endothelium.
- Bacteria frequently isolated from endocarditis cases (e.g., Staphylococcus aureus, Candida species) showed significantly higher adhesion to fibronectin.
- Microorganisms rarely implicated in endocarditis (e.g., Escherichia coli, Pseudomonas aeruginosa) exhibited lower fibronectin binding.
- Microbial adhesion to fibronectin correlated with their ability to cause endocarditis in a rabbit model.
Conclusions:
- Fibronectin is expressed on NBTE and facilitates microbial adhesion.
- This fibronectin-mediated adhesion is an important mechanism in the early pathogenesis of infective endocarditis.
- Fibronectin may serve as a crucial link for circulating microbes to colonize heart valves, initiating infection.