The bacteriology of acute otitis media in children with special reference to Streptococcus pneumoniae as studied by bacteriological and antigen detection methods.

The middle ear fluid (MEF) was studied during an acute attack of otitis media in 519 children, aged 3 months to 6 years. Streptococcus pneumoniae (Pn) was cultured from 39% of the cases; serotypes 19, 6, 3 and 23 were the most common. Haemophilus influenzae (Hi) was cultured in 12%; only 2/64 strains were of type b. Pn were found equally often in all age groups, but Hi were significantly less often isolated in children older than 3 years. The number of negative cultures increased with the age of the child. Pneumococcal capsular polysaccharide was detected with counterimmunoelectrophoresis and/or latex agglutination in 83% of the MEFs from which Pn were cultured, but also in about one third of the MEFs from which no bacteria could be grown. Altogether, with these methods combined Pn were implicated in nearly 60% of the cases of acute otitis media. Gram staining showed polymorphonuclear leucocytes in 85% of pneumococcal otitis cases that were verified by culture but also in 72% of the cases from which no bacteria could be cultured, supporting the contention that also these latter are usually caused by bacteria.