Pathogenesis of implant-associated infection: the role of the host.

Implanted devices are mainly used to improve impaired function or to replace missing anatomic structures. They are made of synthetic material or devitalized biological structures. In contrast to vital transplants, they are not rejected by the body. However, the host reacts against these foreign bodies, a process which can be designated as biocompatibility. The interaction of the device with adjacent granulocytes and complement not only induces various degrees of inflammation but also impairs local microbial clearance. Foreign surfaces are a preferred target for bacterial adherence. While adhering bacteria are highly resistant to the bactericidal activity of phagocytes, they are also resistant to most antimicrobial agents. Certain bacteria may reside within host cells, and hence, evade host defense mechanisms by persisting intracellularly around implants. Nanotechnology minimizes clotting activation and bacterial adhesion by intravascular devices. Furthermore, surface coating with appropriate substances favorably influences biocompatibility as well as susceptibility to infection. In the future, "Microsystems Technology" deployed as intelligent device may decrease the risk of implant failure due to infection.