Biofilms and infections of the upper respiratory tract

Biofilms are microbial communities consisting of bacteria that either are self-reproducing on biological surfaces or are present in the lifeless environment. Biofilms are quite diffuse entities frequently found in human pathological conditions. The formation of bacterial biofilms involves mainly the contamination of artificial medical devices, such as valves and catheters, and their direct implant on mucous membranes, with subsequent development of chronic or recurrent infections. Bacterial biofilms show a complex organization consisting of bacterial cells adherent to a surface and surrounded by a large extracellular matrix mostly made up of polysaccharides and proteins. The resistance observed in biofilms does not appear to be genotypic; instead, it is due to multicellular strategies and/or to the ability of each cell, contained inside the biofilm, to differentiate into a protected phenotypic state which tolerates the antibiotic action. In fact, biofilms are subject to changes following their recurrent exposure to antimicrobial agents, thus incrementing their resistance. Biofilms play an important role in otitis media, sinusitis, chronic cholesteatomatous otitis media, tonsillitis and adenoiditis, thus demonstrating that adenoidectomy may be helpful to children suffering from such a morbid conditions. It is presently estimated that biofilm formation is involved in at least 60% of all chronic and/or recurrent infections. In addition, 30% of the exudates developing in the course of otitis media has shown to be positive for the presence of biofilms; likewise biofilms have been found in tonsillar crypts and in odontostomatologic infections as well. Studies have been carried out on both the use and the efficacy of N-acetylcysteine (NAC) in biofilm breakdown. It has been shown that NAC, used at different concentrations, is able to reduce bacterial adhesion in several anatomical districts.