Bacteria in middle ear effusions in children treated with tympanostomy; a 10-year series.

During the 10-year period, 1983-92, altogether 7,411 ears of 5,291 children with recurrent or chronic otitis media problems were treated with tympanostomy at our hospital in central Finland, The series was divided into three groups: i) infants aged 6-12 months undergoing primary tube treatment. ii) children aged 1 year or more receiving their first ventilation tube(s) in connection with adenoidectomy, and iii) children who had already had ventilation tubes inserted at least once before the present tympanostomy. Middle ear effusion (MEE) samples were obtained from 4,769 (64.3%) of the affected ears, 69.5% of all MEE cultures were negative for bacteria, whereas 20.2% grew pathogenic bacteria. S. pneumoniae was the most frequent pathogen in group 1, whereas H. influenzae was more frequent than S. pneumoniae in groups 2 and 3. In only 3.7% of MEE cultures were beta-lactamase-producing strains of pathogenic bacteria found, either H. influenzae (0.9%) or M. catarrhalis (2.8%). Comparison of the first and second 5-year periods ( 1983-87 vs. 1988-92) showed no significant changes in the occurrence of the various pathogenic bacteria. An increase was observed in beta-lactamase production for M. catarrhalis but not for H. influenzae strains.