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Cytotoxic changes in hair cells secondary to pneumococcal middle-ear infection
R D Cook1, D S Postma, G M Brinson
1Division of Otolaryngology/Head and Neck Surgery, University of North Carolina School of Medicine, Chapel Hill, USA.
Abstract:
To determine whether the bacterial toxins associated with otitis media could induce morphologic changes in the organ of Corti, we inoculated the middle-ear cavities of healthy guinea pigs with either Streptococcus pneumoniae or sterile saline and then examined the organ of Corti histologically at 1, 2, and 3 weeks postinoculation. We found that the outer hair cells (OHCs) in the infected ears underwent several changes that were dependent on both the length of time following inoculation and also the position of the OHCs in the cochlea. At 2 weeks postinoculation, 7.0 to 20% of the OHC nuclei from the infected animals became very swollen, with the most significant swelling occurring in the basal turn. At 3 weeks postinoculation, 2.5 to 3.5% of the OHCs were missing in the infected animals, with the most significant loss occurring in the basal and middle turns. These results suggest that bacterial otitis media can produce cytotoxic changes in the cochlea. These changes may be a clinically significant factor in the temporary and permanent sensorineural hearing loss that has been associated with bacterial otitis media.
Insights
Bacterial toxins from otitis media cause damage to the organ of Corti in guinea pigs. This damage, including outer hair cell swelling and loss, may explain hearing loss associated with this common ear infection.
Area of Science:
- Ototoxicology
- Microbiology
- Neuroscience
Background:
- Otitis media is a common middle ear infection.
- Sensorineural hearing loss is a known complication of bacterial otitis media.
- The specific mechanisms by which bacteria induce cochlear damage remain unclear.
Purpose of the Study:
- To investigate the direct effects of Streptococcus pneumoniae on the cochlear organ of Corti.
- To determine if bacterial toxins can induce morphologic changes in the organ of Corti.
- To correlate observed cochlear changes with potential causes of hearing loss.
Main Methods:
- Healthy guinea pigs were inoculated in the middle ear with Streptococcus pneumoniae or sterile saline.
- The organ of Corti was examined histologically at 1, 2, and 3 weeks postinoculation.
- Morphologic changes in outer hair cells (OHCs) and their nuclei were quantified.
Main Results:
- Infected ears showed time- and position-dependent changes in OHCs.
- At 2 weeks, 7-20% of OHC nuclei were swollen, most significantly in the basal turn.
- At 3 weeks, 2.5-3.5% of OHCs were missing, primarily in the basal and middle turns.
Conclusions:
- Bacterial otitis media can induce cytotoxic changes within the cochlea.
- These bacterial-induced cochlear alterations may contribute to temporary and permanent sensorineural hearing loss.
- The findings highlight a potential direct link between bacterial infection and cochlear damage leading to hearing impairment.