HtrA对乳牙变异链球菌产酸、黏附的体外研究

Influence of HtrA on acid production and adhesion of Streptococcus mutans from deciduous teeth——a study in vitro

目的:探讨HtrA对乳牙变异链球菌产酸、黏附的影响。方法:选用课题组前期筛选并鉴定的乳牙变异链球菌HtrA高毒力株和构建的HtrA基因缺陷株,测定这两组菌株分别在不同pH值的BHI液体培养基中培养48 h后pH值的变化;由荧光标记的乳牙变异链球菌HtrA高毒力株和HtrA基因缺陷株,与被唾液包被的羟基磷灰石共同孵育,测定羟基磷灰石沉淀的荧光值,比较黏附率的差异。结果:在pH值为6.5、7.0时,两组菌株产酸能力的差异无统计学意义(P>0.05);在pH值为5.0、5.5、6.0时,HtrA高毒力株产酸能力强于HtrA缺陷株,差异具有统计学意义(P<0.05);在pH值4.5时,两组菌株产酸能力均受到明显抑制,几乎不产酸,差异无统计学意义(P>0.05)。HtrA缺陷株在唾液包被的羟基磷灰石表面的黏附率[(39.33±1.61)%]低于HtrA高毒力株[(54.67±1.38)%],差异有统计学意义(P<0.05)。结论:HtrA基因的缺陷影响了乳牙变异链球菌非应激状态下的生长能力,并且降低了它的产酸、黏附能力。

Objective: To investigate the influence of HtrA on acid production and adhesion of Streptococcus mutans from deciduous teeth. Methods: The high-virulence HtrA strains and the constructed HtrA-deficient strains ofStreptococcus mutans from deciduous teeth were screened and identified in the previous stage of research, and thepH values of the two strains were measured after 48 hours of culture in BHI liquid medium with different pH values.The fluorescein-labeled high-virulence HtrA strains and HtrA-deficient strains were co-incubated with sali-va-coated hydroxyapatite to measure the fluorescence value of hydroxyapatite precipitate and compare the differ-ence in adhesion rate. Results: At the pH values of 6.5 and 7.0, there was no significant difference in acid-produc-ing ability between the two strains(P > 0.05);at the pH values of 5.0, 5.5, and 6.0, the high-virulence HtrA strainshad a significantly stronger acid-producing ability than the HtrA-deficient strains(P < 0.05). At the pH value of4.5, both strains had a significantly inhibited acid-producing ability, with little acid produced, and there was no sig-nificant difference in acid-producing ability between the two strains(P > 0.05). The HtrA-deficient strains had a sig-nificantly lower adhesion rate on the surface of saliva-coated hydroxyapatite than the high-virulence HtrA strains(39.33% ± 1.61% vs 54.67% ± 1.38%, P < 0.05). Conclusion: HtrA deficiency affects the growth ability of Streptococcus mutans under non-stress state and reduces the acid-producing and adhesion abilities of Streptococcus mutans from deciduous teeth.