[Bacterial biofilms and medical practice]

A suboptimal environment with limited supply of nutrients leads to marked changes in the microbial features. Similar conditions exist also on some tissue surfaces of the human body and on biomedical devices implanted. The basic feature of this environmental adaptation is the adherence of microbes to some surfaces and production of abundant exopolysaccharides. Microbes embedded in this hydrated, mostly anionic polysaccharide matrix called biofilm. The biofilm acts not only by trapping the nutrient or oxygen molecules, but protects the microbes against phagocytic cells, antibodies, biocids, and antibiotics, too. This protected form is responsible for the special nature of normal flora, as well as for some clinical and therapeutic characters of several diseases. Microbes liberated from the biofilm, being in the so called planctonic phase. In cases where the biofilms have developed on biomedical devices such planctonic microbes may cause persistent or relapsing infections. These planctonic microbes can be eliminated by the host responses or by antibiotic treatments, while those in the biofilm cannot, thus serving as a source of further infections.