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One Fundamentals and properties of biofilms

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Overview of biofilm-related problems in medical devices

P. Stoics1, M.C. Chifiriuc2, M. Rapa1, V. Lazar2

1S.C.I.C.P.E. BISTRITA S.A., Bistrita, Romania; 2University of Bucharest, Research Institute of the University of Bucharest-ICUB, Bucharest, Romania

I ntroduction

Microbial adherence to a particular substrate, followed by its colonization and biofilm formation may have a negative impact in many areas, from the industrial to the medical one. Therefore, understanding the mechanisms of adhesion and formation of microbial biofilms is essential for the establishment of effective measures to prevent and combat them (Kaali et al., 2011). Microbial biofilms may be formed at any liquid-solid (e.g., the surface of prosthetic medical devices (MDs), the surface of the stones in the aquatic environment, the ships’ submerged surface), liquid-liquid (oil-water tanks oil), liquid- air (e.g., plant leaves, roots) interfaces, or on the surface of the epithelial and animal tissues (e.g., teeth, digestive and respiratory tract) (Hamilton, 1987; Lazar, 2003). The discovery of microbial biofilms is attributed to Antonie van Leeuwenhoek who, in the 18th century, was the first researcher who examined the so-called “animalcules” in the dental plaque collected from his own teeth, but Costerton et al. (1978), have postulated the general theory of the biofilm formation based on data from the study of microbial biofilms formed in the natural aquatic ecosystems (Lazar, 2003; Sousa et al., 2011). The biofilm is defined as a community of microbial cells attached irreversibly to the substrate at the interface or to each other, embedded in an exopolysaccharidic (EPS) matrix produced by the biofilm cells, which show phenotypic changes (Lazar, 2003). In nature, microorganisms coexist in 99% under the form of biofilms, which suggests resistance and/or a selective advantages for sessile cells compared to their planktonic counterparts. So sessile cells are physiologically different from those who live freely. The main changes in phenotype are linked to gene transcription, growth rate, intensity of the respiration processes and electron transport, synthesis of extracellular polymers, rate of substrate degradation, and the ability to survive in the presence of microbicidal factors (Flemming, 1998; Sousa et al., 2011; Costerton et al., 1987; Hall-Stoodley et al., 2004; Dufrene, 2008; Donlan and Costerton, 2002; Wilson, 2001). The biofilms can contain bacteria, fungi, protozoa, algae, and their associations, usually the constitutive cells requiring similar conditions to initiate the progress of cell growth. The factors that influence the formation of biofilm are very diverse, such as humidity, temperature, pH value of the environment, weather conditions, and the chemical composition of the nutritive substratum. In addition to microorganisms, biofilms contain 80-90% water. Biofilm thickness can vary between 50 and 100 pm, depending on the colonized area (Kaali et al., 2011).

Biofilms and Implantable Medical Devices.

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