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目的 探讨肺炎链球菌的自然转化与其条件致病的关系。方法 采用插入失活的方法制备肺炎链球菌的转化缺陷菌株 ,通过黏附实验和小鼠毒力实验观察它们毒力的变化 ,应用RT PCR测定黏附因子PsaA在野生和缺陷菌株中的表达。结果 实验获得了 3株肺炎链球菌 (1、2和 2 2 )的转化缺陷菌株 (1d、2d和 2 2d)。毒力研究发现转化缺陷菌株对ECV 30 4细胞的黏附能力显著弱于相应的野生菌株 ,1和 2株肺炎链球菌腹腔感染BALB c小鼠的能力显著强于相应的转化缺陷菌株 ;研究还发现PsaA基因在 2和 2 2株肺炎链球菌中的表达量显著高于其缺陷菌株。结论 肺炎链球菌具有自然转化的能力有助于其毒力的表现 ,且可能通过黏附因子PsaA等相关毒力因子表达增加而增强其毒力。
Objective To investigate the relationship between the natural transformation of Streptococcus pneumoniae and its conditional pathogenicity. Methods The defective strains of Streptococcus pneumoniae were prepared by insert inactivation method. The changes of their virulence were observed by adhesion experiments and virulence test in mice. The expression of PsaA was detected by RT PCR in wild and defective strains. Results Three strains of transformation-defective strains of Streptococcus pneumoniae (1, 2 and 2 2) were obtained experimentally (1d, 2d and 22d). Virulence studies showed that the adhesion ability of transformation-deficient strains to ECV 30 4 cells was significantly weaker than that of the corresponding wild-type strains, and the ability of 1 and 2 strains of S. pneumoniae to infect BALB c mice intraperitoneally was significantly stronger than that of the corresponding transformation-deficient strains. The expression level of PsaA gene in 2 and 22 Streptococcus pneumoniae strains was significantly higher than that of the defective strains. Conclusion Streptococcus pneumoniae has the ability of natural transformation contribute to the virulence of Streptococcus pneumoniae, and may enhance its virulence through the expression of PsaA and other related virulence factors.