Prevention of endocardial infection by the use of antimicrobial agents, although desirable, is not always possible. By identifying the patients at  risk, the causative bacteria and the events that induce bacteremia, strategies for prevention of some episodes of IE have been formulated and are routinely recommended even in the absence of supporting clinical trials. Rates of bacteremia are highest for events that traumatize the oral  mucosa followed by those that traumatize the genitourinary tract.The frequency of bacteremia is relatively low for gastrointestinal diagnostic procedures.