Scanning electron microscopy of the cochlea in rats with Streptococcus pneumoniae otitis media

This investigation was performed to determine the morphologic effects of bacterial otitis media on the organ of Corti. The middle ear cavities of rats were inoculated with Streptococcus pneumoniae or saline and the animals were killed on days 1, 4, 7, 10, 14, and 21 after inoculation. Middle ear cultures were obtained and the cochleas were examined using scanning electron microscopy. All animals killed on day 1 had positive cultures, but by day 21, all cultures were negative. Cochlear changes observed were (1) damage to supporting cells (Deiters' cells), (2) morphologic changes of hair cell stereocilia, and (3) loss of inner and outer hair cell stereocilia and cell bodies (to a lesser extent), especially in the lower middle and basal turns. These changes appeared to occur in a definite sequence; ie, damage to the supporting cells, changes in stereocilia, and, finally, hair cell loss. These data show that cochlear damage and hair loss can be associated with bacterial otitis media.