Mucosal biofilm formation on middle-ear mucosa in the chinchilla model of otitis media

Context Chronic otitis media with effusion (OME) has long been considered to be a sterile inflammatory process, The previous application of molecular diagnostic technologies to OME suggests that viable bacteria are present in complex communities known as mucosal biofilms; however, direct imaging evidence of mucosal biofilms associated with OM is lacking. Objective To determine whether biofilm formation occurs in middle-ear mucosa in an experimental model of otitis media. Design and Materials A total of 48 research-grade, young adult chinchillas weighing 500 g were used for 2 series of animal experiments: one to obtain specimens for scanning electron microscopy and the other to obtain specimens for confocal laser scanning microscopy using vital dyes. In each series, 21 animals were bilaterally injected with viable Haemophilus influenzae bacteria and 1 was inoculated to account for expected mortality, Three served as negative controls. Effusions and mucosal specimens were collected from 2 infected animals that were euthanized at 3, 6, 12, and 24 hours and at days 2, 4, 5, 10, 16, and 22 after inoculation. Main Outcome Measures Images were analyzed for biofilm morphology, including presence of microcolony formation and for presence of bacteria on tissue surfaces. Results Scanning electron microscopy demonstrated that biofilm formation was evident in all specimens from animals beginning 1 day after infection and was present through 21 days, Confocal laser scanning microscopy indicated that bacteria within the biofilms are viable. Conclusion These preliminary findings provide evidence that mucosal biofilms form in an experimental model of otitis media and suggest that biofilm formation may be an important factor in the pathogenesis of chronic otitis media with effusion.