Bacteriology of acute otitis media in a cohort of Finnish children followed for the first two years of life

Background Timely information on the bacteriology of primary, noncomplicate d acute otitis media (AOM) may today be needed more than ever, because of t he increasing antimicrobial resistance of its major bacterial causes and be cause of the potential of new pneumococcal and other bacterial vaccines for prevention of AOM. Methods, The study followed 329 children from 2 to 24 months of age at sche duled healthy visits and sick visits at the study clinic. Whenever AOM was diagnosed during the follow-up, myringotomy was performed and middle ear fl uid was aspirated for bacterial culture. Results. At least one middle ear fluid sample was available from 772 AOM ev ents; Streptococcus pneumoniae (Pnc) was isolated in 201 (26%), Moraxella c atarrhalis (Mc) in 177 (23%) and Haemophilus influenzae (Hi) in 174 events (23%). The incidence of Pnc AOM peaked at 12 months of age, whereas the inc idence of Me AOM showed the first peak at 6 months and Hi AOM at 20 months. Pnc AOM showed less prominent seasonality in occurrence than Me and Hi AOM , Hi was a rare cause of the first 2 AOM episodes (13%) but became increasi ngly common from the third episode on (32% on average). Conclusions. Pnc, Me and Hi were almost equally common findings in AOM, Pnc seems to be the most pathogenic of these three, the role of Me is increasi ng and Hi is clearly associated with recurrent AOM.