Genetic relatedness between pneumococcal populations originating from the nasopharynx, adenoid, and tympanic cavity of children with otitis media.

Previous studies have shown that Streptococcus pneumoniae exists in both middle ear effusions and the upper respiratory region from children with otitis media with effusion (OME), but it remains unclear whether these strains represent genetically identical clones. Therefore, it cannot be determined whether these bacteria originate from a common source. To determine the presence of pneumococci at different anatomical locations of OME patients, conventional culture and PCR techniques were used. To analyze the possible genetic relatedness between pneumococci from different anatomical sites, molecular typing by amplified fragment length polymorphism was utilized. The percentage of middle ear effusions of OME patients that are positive for pneumococci after PCR analysis (13%) was higher than after conventional culture (5%). Molecular fingerprints from pneumococci derived from two different anatomic sites within patients were very similar in 80% of OME patients and in 90% of acute otitis medium patients, indicating their genetic relatedness. Biofilm formation or pneumococcal L-forms probably play a role in OME, since culture-negative effusions prove to contain pneumococcal DNA. Bacteria involved in this process most likely originate from the nasopharynx since they show a close genetic relatedness with their nasopharyngeal counterparts.