Viral and Bacterial Polymicrobial Interactions with Streptococcus pneumoniae in Otitis Media

The major pediatric disease otitis media is caused by a variety of bacterial and viral etiological agents, which frequently act in combination to induce polymicrobial middle ear disease. Streptococcus pneumoniae is one of the two most commonly isolated bacterial pathogens of otitis media. This dissertation examines interactions of S. pneumoniae with nontypeable Haemophilus influenzae, the other leading bacterial cause of otitis media, and with adenovirus, a major cause of upper respiratory infections.;Adenoviral infection is a major risk factor for otitis media. We hypothesized that adenovirus promotes bacterial ascension into the middle ear through the disruption of normal function in the Eustachian tubes due to inflammation-induced changes. An intranasal infection model of the chinchilla was used to test the ability of type 5 adenovirus to promote middle ear infection by S. pneumoniae. The hyper-inflammatory adenovirus mutant dl327 and the non-replicating adenovirus mutant H5wt300DeltapTP were used to test the role of inflammation and viral replication, respectively, in promotion of pneumococcal middle ear infection. Precedent infection with adenovirus resulted in a significantly greater incidence of middle ear disease by S. pneumoniae as compared to non-adenovirus infected animals. Infection with the adenovirus mutant dl327 induced a comparable degree of bacterial ascension into the middle ear as did infection with the wild-type virus. By contrast, infection with the non-replicating adenovirus mutant H5wt300DeltapTP resulted in less extensive middle ear infection compared to the wild-type adenovirus. We conclude that viral replication is necessary for adenoviral-induced pneumococcal middle ear disease.;Nontypeable S. pneumoniae which lack the capsular polysaccharide associated with virulence have been isolated from both carriage and disease contexts. Since most cases of otitis media involve more than one bacterial species, we aimed to determine the capacity of a nontypeable S. pneumoniae clinical isolate to induce disease in the context of a single-species infection and as a polymicrobial infection with nontypeable H. influenzae. Using the chinchilla model of otitis media, we found that nontypeable S. pneumoniae colonizes the nasopharynx following intranasal inoculation, but does not readily ascend into the middle ear. However, when we inoculated nontypeable S. pneumoniae directly into the middle ear, the pneumococcus persisted for two weeks post-inoculation and induced otitis media. During coinfection with nontypeable H. influenzae, both species persisted for one week and induced polymicrobial otitis media. This has implications for antibiotic treatment, as we found that nontypeable H. influenzae protected nontypeable S. pneumoniae from amoxicillin in vitro..