Detection of bacterial endocarditis with technetium-99m-labeled antistaphylococcal antibody

The reliable diagnosis of bacterial endocarditis is an important but difficult clinical problem. The potential ability of technetium-99m-labeled antistaphylococcal antibody to detect infective endocarditis was investigated in a rabbit model. Radiolabeling of the purified antibody was effected by a mild electrolytic procedure, with full retention of immunologic activity. Infective endocarditis was induced in rabbits by placing a catheter through the carotid artery into the left ventricle, followed by i.v. injection of Staphylococcus aureus. The labeled antistaphylococcal antibody was subsequently injected, and its clearance and distribution were studied in the infected rabbits and in normal controls. The ratio of radioactivity on the aortic valve to that in the surrounding heart tissue or blood pool was significantly higher for the infected animals (> 10:1) than for the normals, and should permit visualization of the infection site. This radiolabeled antibody technique may provide a feasible approach to detection of infective endocardial lesions.