Phagocytosis and killing of bacteria by middle ear macrophages.

Because macrophage dysfunction has been suggested as one of the underlying pathogenic mechanisms for otitis media with effusion, we have examined macrophage-bacterial interactions using keyhole limpet hemocyanin-induced middle ear macrophages from chinchillas. Our data indicate that macrophages recruited to the middle ear were functional phagocytes capable of discriminate phagocytosis and intracellular killing of eight species of bacteria associated with otitis media, as determined by a fluorochrome microassay. Streptococcus pneumoniae types 14 and 19F, which are associated with the highest relapse frequency in cases of acute otitis media, were the most resistant to phagocytosis. The two organisms most often involved in chronic otitis media (Staphylococcus epidermidis and nontypable Haemophilus influenzae), however, were among the most readily phagocytized isolates. The relative importance of macrophage function in defense of the middle ear, therefore, may be dependent on the causative agent.