Fluorescence “In Situ” Hybridization for the Detection of Biofilm in the Middle Ear and Upper Respiratory Tract Mucosa

Most chronic bacterial infections are associated with biofilm formation wherein the bacteria attach to mucosal surfaces, wound tissue, or medical device surfaces in the human body via the formation of an extracellular matrix. Biofilms assume complex three-dimensional structures dependent on the species, the strain, and the prevailing environmental conditions and are composed of both the bacteria and the extracellular slime-like matrices, which surround the bacteria. Bacteria deep in the biofilm live under anaerobic conditions and must use alternatives to O₂ as a terminal electron acceptor. Thus, the metabolic rates of these deep bacteria are greatly reduced, which renders them extremely resistant to antibiotic treatment, and for reasons not clearly understood, it is often very difficult to culture biofilm bacteria using traditional microbiologic techniques. To directly identify and visualize biofilm bacteria in a species-specific manner, we developed a confocal laser scanning microscopy (CLSM)–based 16S rRNA fluorescence in situ hybridization (FISH) protocol, to find biofilm bacteria in middle ear and upper respiratory tract mucosa, which preserves the three-dimensional structure of the biofilm and avoids the use of traditional culture techniques.