PRESENCE OF A BIOMATERIAL IMPLANT FACILITATES INDUCTION OF EXPERIMENTAL INFECTIVE ENDOCARDITIS DUE TO STREPTOCOCCI AND STAPHYLOCOCCI

Infective endocarditis (IE) usually is studied using animals with cath eters inserted into the heart, which causes formation of platelet-fibr in 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 cath eter before bacterial challenge, or leaving the catheter in place. In all cases, removal of the catheter caused a strong decrease in the fre quency of IE. The presence of the catheter stimulated population incre ase of streptococci within 4 h after challenge. As most catheters were sterile 4 h after challenge, they did not serve as a reservoir of bac teria. To study the requirement of a preformed VG catheters were inser ted either 24 h or 30 min before bacterial challenge. In the former mo del VGs were present, in the latter VGs were not yet formed when bacte ria 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, in dicating that a preformed VG is not necessary for development of IE. F ive 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 br colonization of the aortic valve, but reflects di fferences in persistence after initial colonization. Like in the 24 h model, persistence of the bacteria was greatly enhanced by the continu ous presence of the catheter. Possible mechanisms of the infection-pot entiating effect of the catheters are discussed.