Adhesin Expression in Matched Nasopharyngeal and Middle Ear Isolates of Nontypable Haemophilus influenzae from Children with Acute Otitis Media † 866

Abstract

The HMW1 and HMW2 proteins, Hia, and hemagglutinating pili are important adherence factors in nontypable H. influenzae. To gain insight into the relative importance of these adhesins in nasopharyngeal colonization and localized respiratory tract disease, we assessed their expression in simultaneous nasopharyngeal and middle ear isolates of nontypable H. influenzae from 17 children with acute otitis media. In all patients, including 11 with bilateral disease, the matched isolates were isogenic based on total protein profiles and genomic fingerprints. Of the nasopharyngeal isolates, 14 expressed only HMW1/HMW2-like proteins, one expressed only Hia, one expressed only pili, and one expressed both Hia and pili. Further analysis revealed concordance between nasopharyngeal isolates and the matched middle ear isolates for expression of HMW1/HMW2-like proteins and Hia. In contrast, in the two children with piliated organisms colonizing the nasopharynx, the corresponding middle ear isolates were nonpiliated and could not be enriched for piliation. Nevertheless, Southern analysis revealed that these two middle ear isolates contained all five hif genes required for pilus biogenesis and had no evidence of major genetic rearrangement. In summary, the vast majority of isolates of nontypable H. influenzae associated with acute otitis media express HMW1/HMW2-like proteins, with expression present in both the nasopharynx and the middle ear. A minority of isolates express Hia, again both in the nasopharynx and the middle ear. A smaller fraction of isolates express pili, which are irreversibly inactivated upon transit from the nasopharynx to the middle ear. We speculate that the HMW adhesins and Hia are important at multiple steps in the pathogenesis of otitis media, while pili contribute to early colonization and then become dispensible.