Interaction between Streptococcus pneumoniae and Branhamella catarrhalis obtained from double-colonized, healthy nasopharynx and double-infected, diseased middle ear cavity.

Streptococcus pneumoniae and Branhamella catarrhalis were obtained from the double-colonized nasopharynx of 3 healthy carriers and from the double-infected middle ear cavity of 3 patients suffering from acute otitis media. The bacterial strains were isolated and injected both separately and together into brain-heart infusion broth. Separately injected, both S. pneumoniae and B. catarrhalis survived in the broth for at least 48 h. When injected together, B. catarrhalis was completely suppressed after 16-24 h, whereas S. pneumoniae survived for at least 48 h. Thus S. pneumoniae had a remarkable inhibitory growth effect on B. catarrhalis, which can explain why double-infected middle ear cavities so seldom are found during acute otitis media.