Effect of influenza A virus infection on nasopharyngeal colonization and otitis media induced by transparent or opaque phenotype variants of Streptococcus pneumoniae in the chinchilla model

Phase variation in the colonial opacity of Streptococcus pneumoniae has bee n implicated as a factor in bacterial adherence, colonization, and invasion in the pathogenesis of pneumococcal disease. Additionally, the synergistic effects of influenza A virus and S. pneumoniae in the development of otiti s media (OM) have been reported. This study examined the ability of opaque or transparent S. pneumoniae from the same strain in combination with an an tecedent influenza A virus infection to colonize the nasopharynx and invade the middle ear in the chinchilla model. Our data indicated that there was no significant difference in the level of nasopharyngeal colonization and i nduction of OM between the opaque and transparent variants unless there was a prior challenge with influenza A virus. Subsequent to influenza A virus infection, there was a significant difference between the variants in the a bility to colonize and persist in the nasopharynx and middle ear. The conce ntrations of the opaque variant in nasopharyngeal-lavage samples and middle -ear fluid remained consistently higher than those of the transparent varia nt for 10 days postinoculation. Data from this study indicate that the effe cts of influenza A virus on the pathogenesis of experimental S. pneumoniae- induced OM differ depending on the opacity phenotype involved.