Experimental Endocarditis in Calf after Tricuspid Valve Replacement

A calf model for reproducible, prosthetic tricuspid valve endocarditis was developed using Staphylococcus aureus. The course of late prosthetic valve endocarditis was characterized as a fulminant disease when untreated with antibiotics. The earliest sign of a colonized valve prosthesis was an elevation of body temperature, which correlated with occurrence of positive blood cultures. The dose required to colonize an endothelialized tricuspid prosthetic valve in the calf model was 10⁷ to 10⁸S. aureus organisms. In the model for late prosthetic valve endocarditis, silver-allantoin-heparin (SAH) treatment of the prosthetic valve gave no protection from inoculums of 10⁸S. aureus injected 60 days after operation. SAH treatment may be beneficial in early stages of prosthetic valve endocarditis, but this requires further study. Simultaneous cultures from the right atrium, the right ventricle, and the aorta of 2 animals showed that there was a 1,000- to 10,000-fold decrease in the bacterial titers across the combined pulmonary and systemic capillary beds. Bacterial titers drawn from the jugular vein had a 46% false negative result, and positive cultures from the external jugular vein showed only 1.3 S. aureus organisms per milliliter of blood. These bacteriological findings point out the risks of depending on sampling from the peripheral venous system when culturing for right heart endocarditis.