Viability and virulence of pneumolysin, pneumococcal surface protein a, and pneumolysin/pneumococcal surface protein a mutants in the ear

IMPORTANCE: Understanding how pneumococcal proteins affect the pathology of the middle ear and inner ear is important for the development of new approaches to prevent otitis media and its complications. OBJECTIVES: To determine the viability and virulence of Streptococcus pneumoniae mutants deficient in pneumolysin (Ply^-) and pneumococcal surface protein A (PspA ^-) in the chinchilla middle ear. DESIGN: Bullae of chinchillas were inoculated bilaterally with wild-type (Wt), Ply^-, PspA^-, and Ply^-/PspA^- strains. Bacterial colony-forming units (CFUs) in middle ear effusions were counted at 48 hours. The CFUs of the PspA^- group were also counted at 6 to 36 hours after inoculation. Temporal bone histopathological results were compared. SETTING AND PARTICIPANTS: Twenty-seven chinchillas in an academic research laboratory. EXPOSURE Chinchilla middle ears were inoculated with S pneumoniae to produce sufficient volumes of effusions and noticeable histopathological changes in the ears. MAIN OUTCOMES AND MEASURES: The CFU counts in the middle ear effusions and histopathological changes were compared to determine the effect of pneumococcal protein mutations on chinchilla ears. RESULTS: At 48 hours, CFUs in middle ears were increased for the Wt and Ply^-/PspA^- strains, but Ply^- remained near inoculum level. No bacteria were detected in the PspA^- group. The CFUs of PspA^- decreased over time to a low level at 30 to 36 hours. In vitro, PspA^- in Todd-Hewitt broth showed an increase in bacterial growth of 2 logs at 43 hours, indicating PspA^- susceptibility to host defenses in vivo. The PspA^- and Ply^- groups had fewer pathologic findings than the Wt or Ply ^-/PspA^- groups. Histopathological analysis showed significant differences in the number of bacteria in the scala tympani in the Wt group compared with the Ply^-, PspA^-, and Ply ^-/PspA^- groups. The PspA^- strain was the least virulent. CONCLUSIONS AND RELEVANCE: The PspA^- mutant was much less viable and less virulent in the ear than the Wt, Ply^-, and Ply ^-/PspA^- strains. There was no significant attenuation in the viability and virulence of the Ply^-/PspA^- mutant compared with the Wt or single mutants. The viability and virulence of pneumococcal mutants seemed to be protein and organ specific.