الفهرس 
BiofilmsOnly 14 pages are availabe for public view
 |  | from | 109 |  |  |
| | | from | 109 | | |
Abstract
The ability of unicellular bacterial species to co-ordinate their responses and to act as a multicellular population provides protection to bacteria. A mechanism by which bacteria can function as a multicellular population is to form a biofilm, which is a community of bacterial cells that are adherent to surface, interface or each other and are encased in a self-produced polymeric matrix. Bacteria in biofilms can sense the presence of each other by quorum sensing. Gene transfer takes place inside biofilms so that, bacteria have different phenotypes and differ metabolically from the planktonic ones. In this form they are resistant to host immune system and antimicrobial therapy. Biofilm is the predominant form of life for many microorganisms in a hydrated biologic system. Most of bacteria can form a biofilm when given the right condition, the most famous are S-aureus, S-epidermidis, Streptococcus, P-aeroginosa, Lactobacilli and Candida species. Human diseases due to biofilms are usually associated with the presence of some implantable medical device for example catheters and joint prostheses or as a consequence of impairment of host defence system as in cystic fibrosis patients, ulcers in diabetic patient and chronic wounds.
The structure of biofilm can range from the relatively feasureless flat type to more complex organization involving mushroom like aggregates separated by water channels. Bacterial biofilm formation is regulated at four main steps: surface attachment, microcolony formation, biofilm maturation and biofilm architecture formation.
Fungal biofilms are usually associated with indwelling medical devices like ocular lenses central nervous system shunts. They proceed in three developmental phases: early from 0-11 hours, intermediate from 12-30 hours and mature from 38-72 hours. Fungal biofilms resist antifungal treatment.
Open skin wounds have lost many of the protective defence mechanisms of intact skin and are colonized with microbial organisms. The wound environment supports biofilm life cycle, it has the characteristics that facilitate biofilm formation like attachment, proliferation and quorum sensing. Chronic wounds provide a nutrient-poor and fibrin rich environment that trigger bacteria to form biofilm which can easily attach to the fibrin surface.
Implanted prosthetic devices are platform for the development of a bacterial biofilms. Penile prostheses infections can be present in two ways: clinically apparent or subclinical infection.
Various advanced microscopic techniques are used to visualize biofilms, These include scanner laser confocal microscopy, deconvolution fluorescence microscopy, epifluorescence microscopy, fluorescent microscopy and electron microscopy combined with confocal microscopy. Molecular techniques are used to detect bacterial nucleic acid in samples from infected patients.
Antibiotics by themselves are often unable to kill all of the bacteria in a biofilm so active research is concerned with ways of enhancing the activity of these agents. It has been shown that exposing biofilms to electric current or to ultrasound in the presence of antibiotics has a synergistic effect that can achieve killing of all of the organisms in the biofilm. It often known that prevention is better than cure.
Researches will continue to get benefit of biofilm in medical and industerial researches and to find the most effective method of treatment of diseases caused by bacterial and fungal biofilms.
Conclusion
So we conclude that biofilm and its ability to resist antimicrobial agents and host immune system is the major cause of mortality from nosocomial chronic infections and infections accompanying prosthetic devices like catheters and heart valves. With advances in technology we can detect the presence of biofilm, possibly the genes involved in its structure and structure of genes encoded with quorum sensing and this will help in better control and treatment of diseases caused by biofilm infections.