Effects of monocytopenia and anticoagulation in experimental Streptococcus sanguis endocarditis

The role of blood monocytes in the attachment of streptococci to endocardial vegetations was investigated in an experimental Streptococcus sanguis endocarditis by depletion of blood monocytes with the cytostatic drug VP 16-213 alone and combined with anticoagulant treatment with warfarin sodium. The numbers of streptococci in the vegetations of control, monocytopenic, and monocytopenic/anticoagulated rabbits were comparable. In the vegetations streptococci were found mainly in areas free of phagocytic cells. It is concluded that streptococci do not have to be phagocytosed by monocytes in the circulation before being deposited on the surface of endocardial vegetations. Even the vegetations of intensively anticoagulated/monocytopenic rabbits showed colonies of streptococci embedded in polymerized fibrin and cellular material, this matrix possibly being held together by streptococcal dextran.