[Inner ear damage induced by bacteria (Mycobacterium chelonae)]

Mycobacterium chelonae has a pathogenicity for mouse inner ear, resulting in "spinning disease". The mice were subjected to intravenous injection of 1-1.2 x 10(7) organisms of strain ATCC19977 of M. chelonae subspecies abscessus. Morphological changes in the inner ear were investigated together with changes in behavior and auditory brainstem response (ABR). Three days after injection, the threshold of ABR rose in high frequency and the latency of the fifth wave prolonged. The behaviors of the mice such as "grooming" or "sniffing" were suppressed day by day. Fourteen days after injection, 35% of mice showed abnormal behavior, such as "spinning disease". The damage in the cochlear and vestibular sensory cells were observed using scanning electron microscopy and light microscopy. The inner ear showed serous or purulent labyrinthitis after injection. The most specific change found in purulent labyrinthitis was massive abscess of the cochlea with necrosis. Serous labyrinthitis which might have been induced by bacterial toxins was characterized by homogeneous and eosinophilic precipitates and slight cellular infiltrations in the perilymphatic and endolymphatic spaces. In the organ of Corti, the inner and outer hair cell cilia had degenerated and disappeared. In the vestibular end organs, the sensory cilia were fused, lost and sustained ballooning. The cross links and rough nature of the sensory hair membrane had disappeared in the early stage of serous labyrinthitis.