Infective endocarditis (IE) usually is studied using animals with catheters inserted into the heart, which causes formation of platelet-fibrin thrombi (vegetations, VGs). We used two rabbit models to study the respective roles of the catheter and the VGs in the development of IE. The influence of the catheter was studied by either removing the catheter before bacterial challenge, or leaving the catheter in place. In all cases, removal of the catheter caused a strong decrease in the frequency of IE. The presence of the catheter stimulated population increase of streptococci within 4 h after challenge. As most catheters were sterile 4 h after challenge, they did not serve as a reservoir of bacteria. To study the requirement of a preformed VG catheters were inserted either 24 h or 30 min before bacterial challenge. In the former model VGs were present, in the latter VGs were not yet formed when bacteria were injected. The frequencies of IE due to 2 S. sanguis and 2 S.epidermidis strains in the 24 h model or 30 min model were similar, indicating that a preformed VG is not necessary for development of IE. Five coagulase-negative stains were shown to vary in their capacity to cause IE in the 30 min model. Variation was not caused by differences in early adhesion or colonization of the aortic valve, but reflects differences in persistence after initial colonization. Like in the 24 h model, persistence of the bacteria was greatly enhanced by the continuous presence of the catheter. Possible mechanisms of the infection-potentiating effect of the catheters are discussed.
|Journal of Materials Science: Materials in Medicine
|Published - 1995