Opsonization and phagocytosis of bacteria during various middle ear infections.

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.