What Does Infective Endocarditis Look Like?
When endocarditis occurs, small masses called vegetations form at the site of infection (Figure 1 and Figure 2). When vegetations are viewed under a microscope, generally one sees the microorganism that causes the infection embedded in a meshwork of fibrin and other cellular material similar to that used by the body to form blood clots. White blood cells that the body uses to fight infection are uncommon, a finding which explains the need to give antibiotics over many weeks to kill the infecting organism and cure endocarditis. The absence of white blood cells in vegetations is not fully explained but likely relates in part to the dense nature of the vegetation tissue, which in turn restricts the migration of these cells. Also, the bacteria causing endocarditis are buried in a nongrowing state deep in the vegetation. In this state they do not generate the intense chemical signals that usually promote the migration of white cells to a site of infection.
