Gross and microscopic lesions of middle and inner ear infections in swine.

In all infected middle ears from 36 swine, there was purulent material in the tympanic cavity and tympanic bulla. Frequently, there were lysis of the tympanic membrane and ossicles and purulent material in the external ear canal. Sometimes, there were desquamation of the stratified squamous epithelium lining the tympanic cavity, and osteolysis of the underlying osseous wall with subsequent fibrosis. In those swine with inner ear infections, there were infiltration of neutrophils and fibrin in the cochlea and vestibule. The predominant isolation from the infected middle ears was non-groupable beta-hemolytic streptococci, although isolations of streptococcic groups C, E, and G, Pasteurella multocida, and Corynebacterium pyogenes were made.