Immunoglobulin- and complement-coated bacteria in middle ear effusions during the early course of acute otitis media

We used an immunofluorescence assay to investigate the content of secretory IgA- (SIgA), IgG-, IgM- and C3b-coated bacteria in middle ear effusions obtained within 12-72 h after the onset of acute symptoms of purulent otitis in 28 patients (37 ears). Simultaneously we analyzed the bacteria, both qualitatively and quantitatively, using standard culturing methods and fluorescein conjugated (FITC) antibodies to Haemophilus influenzae and Streptococcus pneumoniae. The ages of the patients were in the range of 5 months to 17 years; 18 were males and 10 females. 73% of the samples harboured no antibody- or C3b-coated bacteria, and particularly those of young patients (< 20 months). 92% of the samples were culture-positive, while 8% showed dormant bacteria. The predominant species were S. pneumoniae and H. influenzae. In 8% of the samples there was heavy and in 11% slight peripheral SIgA-coating of the 5% showed heavy and 19% slight peripheral IgG-coating. Only 3 samples were intensely opsonized, i.e. the bacteria were coated with IgG and C3b simultaneously. In most cases of acute purulent otitis media, the middle ear cavity of young individuals is not able to coat pathogens with SIgA, IgG, IgM and C3b during the early course of infection.