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draft page About biofilms Certain microorganisms can irreversibly adhere to a submerged surface and differentiate to form a complex, multicellular structure called a biofilm. The surface may be inert, nonliving material or living tissue. A biofilm consists of microbial cells (algal, fungal, bacterial) and the extracellular biopolymer these cells produce. Bacteria attach to surfaces by proteinaceous appendages referred to as fimbriae. Once a number of fimbriae have “glued” the cell to the surface, detachment of the organism becomes very difficult. Then the organisms begin to produce extracellular polymers (sometimes called “slime”) that facilitate adhesion and provide a structural matrix. The slime consists primarily of polysaccharides and water. The amount of biopolymer produced can exceed the mass of the bacterial cell by a factor 100 or more. The biofilm structure provides a favourable protective environment for the survival of the cells of the organism. For some applications biofilm formation is very useful, like in reactors for water purification and in the production of biochemicals. However, in industry biofilms are also notorious for causing pipe plugging and corrosion. Biofilms happily colonize many household surfaces, including toilets, sinks and cutting boards in the kitchen and bath. Ineffective cleaning may increase the incidence of illness associated with pathogenic organisms coming from these surfaces. Biofilms on the surfaces of catheters, medical implants, wound dressings or other types of medical devices are often responsible for infections. Biofilms are very tenacious and highly resistant to antibiotics. Besides, detachment of the biofilm from the device may result in infection. Research has shown that virtually all indwelling catheters are colonized by microorganisms embedded in a biofilm matrix. These organisms originate from the patient’s skin microflora, exogenous microflora from health-care personnel, or from contaminated infusates. They gain access to the catheter by migration externally from the skin along the exterior catheter surface or internally from the catheter hub or port. Although medical devices may differ widely in design and use, specific factors determine susceptibility to biofilm formation. For example duration of use, number and type of organisms to which the device is exposed, flow rate and composition of the medium in or on the device, device material construction and conditioning films on the device all may influence biofilm formation. Better understanding of these mechanisms should lead to more effective biofilm control strategies and a clearer picture of the importance of biofilms in public health.
Figure 1: SEM picture of biofilm
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