A rat model for bacterial otitis media.
Rat middle ear was exposed to challenge with viable pneumococci, type 3 and 6A, and the course of changes in the middle ear was observed by otomicroscopy and analysis of bacterial samples from blood, nasopharynx and middle ear effusions. Microscopical examination of changes in the middle ear mucosa during and after the acute infection was also made. Depending on the type and concentration of pneumococci, three different results were observed: otitis media with purulent effusion, otitis media with serous effusion, or no reaction at all. The mortality rate was low and most animals recovered within 10 days without postinfectional changes visible by otomicroscopy. The microscopical examination of the middle ear mucosa revealed distinct changes. Inoculation of rat middle ear with pneumococci causes a self-limiting infection that closely resembles acute otitis media in the human. Thus the rat would seem to be a suitable animal model for the study of bacterial otitis media.