The effect of transformation on virulence of Streptococcus pneumoniae

Objective The effect of pneumococcal transformation on its pathogenesis was investigated. Methods Three transformation-deficient strains No.1d, 2d and 22d were established by the insertion of inactivating gene comE. The virulence of transformation-deficient strains were compared with the wild ones by challenging mice through intraperitoneal route, by adhering to ECV 304 cells in vitro and by detecting their gene PsaA mRNA expression. Results In comparison with the wild strains, the adherence rates of all transformation-deficient strains to ECV 304 cell were significantly reduced(P0.05), the median survival time of No.1d and 2d strains significantly increased by challenging mice through intraperitoneal route (P0.05), and the mRNA expressions of PsaA were reduced (P0.05) in No.2d and 22d strains. Conclusion These results indicated that transformation might affect the virulence expression in S.pneumoniae.