Evaluation of the virulence of a Streptococcus pneumoniae neuraminidase-deficient mutant in nasopharyngeal colonization and development of otitis media in the chinchilla model

Considerable evidence has implicated Streptococcus pneumoniae neuraminidase in the pathogenesis of otitis media (OM); however, its exact role has not been conclusively established. Recently, an S. pneumoniae neuraminidase-def icient mutant, Delta NA1, has been constructed by insertion-duplication mut agenesis of the nanA gene of S. pneumoniae strain D39. The relative ability of Delta NA1 and the D39 parent strain to colonize the nasopharynx and to induce OM subsequent to intranasal inoculation and to survive in the middle ear cleft after direct challenge of the middle ear were evaluated in the c hinchilla model. Nasopharyngeal colonization data indicate a significant di fference in the ability of the Delta NA1 mutant to colonize as well as to p ersist in the nasopharynx. The neuraminidase-deficient mutant was eliminate d from the nasopharynx 2 weeks earlier than the D39 parent strain. Both the parent and the mutant exhibited similar virulence levels and kinetics duri ng the first week after direct inoculation of the middle ear. The Delta NA1 neuraminidase-deficient mutant, however, was then completely eliminated fr om the middle ear by day 10 postchallenge, 11 days before the D39 parent st rain. Data from this study indicate that products of the nanA gene have an impact on the ability of S. pneumoniae to colonize and persist in the nasop harynx as well as the middle ear.