Turnover of Haemophilus influenzae isolates in otitis-prone children

Arbitrarily primed PCR with primer ERIC2 and RAPD Ready-to-Go beads was applied to study the epidemiology of non-typable Haemophilus influenzae (NTHI) isolated from the nasopharynx of children with recurrent otitis media (otitis-prone children). Thirty-five otitis-prone children (OP-children) were included. Three pairs of siblings were identified in the study population. This study is part of a large prospective multicentric trial investigating the efficacy of a new conjugated pneumococcal vaccine in OP-children (OMAVAX trial). During a 2-year study period, NTHI strains were isolated from nasopharyngeal swabs and, when possible, middle ear aspirates were collected in OP-children between 1 and 6 years of age. In 20 out of the 35 children, 48 H. influenzae isolates were obtained simultaneously from different sites (left and/or right ear and/or nasopharynx) of the same child as well as from siblings or during initial and follow-up visits of the same child. Subsequent genotyping indicated substantial genetic diversity among the H. influenzae isolates studied, since for a total of 48 isolates in 20 OP-children, 29 different genotypes were observed. Simultaneous isolation for different sampling sites (ear or nasopharynx) as well as for siblings resulted mostly in identical fingerprints. Longitudinal follow-up of H. influenzae isolates in the nasopharynx almost always resulted in different genotypes. We can therefore conclude that both cross colonization (between sampling sites within the same patient and between siblings) and turnover of H. influenzae isolates are high in OP-children.