Bacterial aetiology of chronic otitis media with effusion in children - risk factors.

Background: Otitis media with effusion (OME) may occur spontaneously because of poor Eustachian tube function or as an inflammatory response following AOM. Bacterial involvement in OME has been widely reported, with various available methods to identify pathogens from middle ear effusion, including traditional culture methods and polymerase chain reaction (PCR).

Objectives: The primary goal of this study was to evaluate the bacteriological profile of middle ear effusion in OME. Risk factors of the bacterial OME aetiology were also identified.

Methods: Middle ear effusions (MEF) from 50 children, aged 2-8 years, diagnosed by ENT and undergoing routine tympanostomy tube placement were collected. MEF samples were streaked on standard microbiological media. Next, DNA was isolated from MEF samples and analysed with multiplex PCR for Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Alloiococcus otitidis.

Results: In multiplex PCR assay 37 (74%) of 50 children were positive for at least one of the four microorganisms. In 27.0% positive children multiple bacterial pathogens were identified. A. otitidis was the most frequently identified in positive MEF children (59.5%). By multiplex PCR, H. influenzae, S. pneumoniae and M. catarrhalis were detected in 24, 18 and 8% of OME patients, respectively. There was significant association between bilateral infection and H. influenzae aetiology of OME.

Conclusions: Overall we found OME predominantly a single otopathogen infection caused mainly by A. otitidis, which is difficult in identification using standard culture method, ahead to S. pneumoniae and H. influenzae. However, one third of MEF samples had multiple bacterial pathogens.