Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978.
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