Biofilm has been shown to be important in prosthetic infections, dental plaque and cystic fibrosis; it has now been found in an animal model of otitis media (OM). Researchers in the United States injected H. influenzae into the middle ears of chinchillas. Starting treatment with ampicillin 72 hours later rendered any effusion culturally sterile. Pairs of chinchillas were killed at 10 intervals, three hours to three weeks after being infected, and their eardrums removed. Scanning electron microscopy showed biofilm formation in all of the animals which had developed middle ear effusions. Microcolony formation was evident after 24 hours, and by five days mature biofilm was present, with tower-type structures consisting of many layers of bacteria in an exopolysaccharide matrix. Frozen specimens were stained (so that, with confocal laser scanning microscopy, live bacterial cells appeared green and dead cells red), showing viable bacteria within the biofilm.
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