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Peptidoglycan isolated from nontypeable Haemophilus influenzae induces experimental otitis media in the chinchilla
Abstract:
Bacterial cell wall components induce a number of biologic effects and promote inflammatory changes in a variety of hosts. Peptidoglycan isolated from Streptococcus pneumoniae can induce inflammation in the middle ear; however, an analogous role for peptidoglycan derived from gram-negative otitis media pathogens has not been described. Peptidoglycan isolated from nontypeable Haemophilus influenzae (NTHi), a major cause of otitis media, was evaluated in a chinchilla model. The direct injection of the middle ear with 3-300 micrograms of peptidoglycan resulted in tympanic membrane inflammation, abnormal pressure in the middle ear, leukocytosis, and histopathologic changes in the middle ear mucosa that included marked edema, osteoneogenesis, focal hemorrhage, and a mononuclear infiltration into the subepithelial space. These data indicate that NTHi peptidoglycan induced inflammation and histopathologic changes in the tympanic membrane and middle ear mucosal epithelium and may contribute to the pathogenesis of otitis media.
Insights
Nontypeable Haemophilus influenzae (NTHi) peptidoglycan causes middle ear inflammation and tissue damage. This finding suggests NTHi peptidoglycan contributes to the development of otitis media.
Area of Science:
- Microbiology
- Immunology
- Otolaryngology
Background:
- Bacterial cell wall components, like peptidoglycan, trigger host inflammatory responses.
- Peptidoglycan from Streptococcus pneumoniae is known to cause middle ear inflammation.
- The role of peptidoglycan from Gram-negative otitis media pathogens remained unclear.
Purpose of the Study:
- To investigate the inflammatory potential of peptidoglycan from nontypeable Haemophilus influenzae (NTHi).
- To determine if NTHi peptidoglycan contributes to the pathogenesis of otitis media.
Main Methods:
- Evaluation of NTHi peptidoglycan in a chinchilla animal model.
- Direct injection of varying doses (3-300 micrograms) of NTHi peptidoglycan into the middle ear.
- Assessment of tympanic membrane, middle ear pressure, and histopathological changes.
Main Results:
- NTHi peptidoglycan induced tympanic membrane inflammation and abnormal middle ear pressure.
- Leukocytosis and significant histopathologic changes were observed in the middle ear mucosa.
- Changes included edema, osteogenesis, hemorrhage, and mononuclear cell infiltration.
Conclusions:
- NTHi peptidoglycan directly induces inflammation and pathological changes in the middle ear.
- These findings suggest a significant role for NTHi peptidoglycan in the pathogenesis of otitis media.