Bacteremia may be caused by entry of organisms at the skin site of percutaneous catheters or leads, via the catheter lumen, or in contaminated infusate. Microorganisms carried by the bloodstream enter the right side of the heart, poten- tially causing IE on preexisting NBTE. IE can also occur as a result of direct infection of an indwelling device. This occurs at the time of device placement into a cardiac locus (eg, valves, leads, other types of devices) and is an example of surgical site infection. These infections can occur despite the administration of antibiotic prophylaxis at the time of placement of cardiovascular devices such as heart valves, pacemaker leads, or left ventricular devices. Adhesins Virulence factors that are involved in bacterial adherence, so- called adhesins, have received the bulk of recent investigative attention. Advances in molecular biological techniques have been crucial in characterizing these cell surface structures, with attention specifically to staphylococcal, streptococcal, and enterococcal species, which account for the large majority of IE cases. These adhesins attach to either host cell structures or extracellular molecules that bind to host cells or to extracel- lular matrix. The availability of an experimental animal model of endocarditis has been a pivotal aspect of these pathogenesis investigations. It has served as the ultimate evaluation of in vitro molecular techniques to obtain mutant and recombinant isolates that are developed to examine the effects of a single purported virulence factor expressed by a wild-type strain. Considering the fact that Gram-positive cocci typically express multiple adhesins, the ability to demonstrate the role of a single adhesin in infection pathogenesis is remarkable. For example, this approach demonstrated pilus involvement in attachment to collagen by Streptococcus gallolyticus. 