Relevance, pathogenicity and virulence of microorganisms in implant related infections

It is impossible to imagine modern medicine today without indwelling devices of various kinds. The time that these implants or prostheses remain in the patient's body can vary from a few hours, e.g. intravenous catheter, to his entire life, e.g. hip prosthesis, heart valve. Besides the indisputable use and advantages of this type of medical intervention for the patient, e.g. saving his life or improving its quality, the associated complications should not be overlooked. One of the most frequent and significant complications of implant surgery is the manifestation of infection in the tissue around the implant. That infection occurs is not surprising since the indwelling devices predispose to bacterial and mycotic infection on the one hand and impede its eradication on the other. The consequences of infection for the patient may mean the loss of regained mobility and independence, hospitalization for sepsis, or even death. Microbes per se are not necessarily pathogenic, however, there are numerous virulence factors which affect the degree of pathogenicity of the microorganisms. These include, for example, various enzymes, (e.g. catalase, hyaluronidase, collagenase and other proteases), and specific surface structures, e.g. the polysaccharide capsules of pneumococci or the lipopolysaccharides of Gram negative bacteria, and the production of bacterial toxins, e.g. leucozidin, streptolysine. The strategies which the pathogenic bacteria employ in their efforts to occupy the host include adherence, penetration and multiplication, antiphagocytosis and serum resistance, the formation of siderophores, antiimmunity, and cell and tissue damage. An attempt will be made here to present an overview of this multifactorial event in which the host obviously plays an important role.