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Opsonization and phagocytosis of bacteria during various middle ear infections
1Department of Otolaryngology, Central Hospital of Keski-Pohjanmaa, Kokkola, Finland.
Abstract:
Samples of middle ear effusions (MEE) obtained from 50 children suffering from acute purulent otitis media (AOM; 23 ears), otitis media with effusion (OME; 15 ears) or chronic suppurative otitis media (COM; 23 ears) were subjected to cytological (cellular differentiation, degree of phagocytosis) and bacteriological (species quantification and identification, degree of opsonization) analyses. Methods used were direct microscopy of acridine orange stained material, immunofluorescence assay using fluorescein-labelled antibodies to immunoglobulin G (IgG) and complement cleavage product C3b, and standard bacterial culturing on agar plates. The most intense opsonization and phagocytosis was evident in COM effusions culture-positive for Staphylococcus aureus. AOM and OME effusions showed rather poor opsonization and roughly 1% of the phagocytes harboured intracellular bacteria. COM effusions, culture-positive for Pseudomonas aeruginosa, showed no bacterial opsonization or phagocytosis whatsoever. Opsonization and phagocytosis of bacteria in the middle ear cleft is highly species-specific.
Insights
Middle ear effusion analysis reveals bacterial opsonization and phagocytosis vary by infection type. Chronic suppurative otitis media with Staphylococcus aureus showed the most bacterial clearance, unlike Pseudomonas aeruginosa.
Area of Science:
- Otolaryngology
- Microbiology
- Immunology
Background:
- Middle ear effusions (MEE) in children can result from acute purulent otitis media (AOM), otitis media with effusion (OME), or chronic suppurative otitis media (COM).
- Understanding the host's immune response within the middle ear is crucial for managing these conditions.
Purpose of the Study:
- To investigate the cellular and bacterial characteristics of MEE in different pediatric otitis media subtypes.
- To assess the levels of opsonization and phagocytosis of bacteria within the middle ear cleft.
Main Methods:
- Cytological analysis of MEE from 50 children (AOM, OME, COM) for cellular differentiation and phagocytosis.
- Bacteriological analysis including species identification, quantification, and opsonization assessment.
- Microscopy, immunofluorescence assay (IgG, C3b), and bacterial culturing were employed.
Main Results:
- High opsonization and phagocytosis were observed in COM effusions positive for Staphylococcus aureus.
- AOM and OME effusions demonstrated poor opsonization, with only ~1% of phagocytes containing intracellular bacteria.
- COM effusions infected with Pseudomonas aeruginosa showed no evidence of bacterial opsonization or phagocytosis.
Conclusions:
- The capacity for bacterial opsonization and phagocytosis in the middle ear is highly dependent on the specific bacterial species involved.
- Immune clearance mechanisms differ significantly across AOM, OME, and COM, particularly concerning S. aureus and P. aeruginosa.