甘草酸对酸性环境中变异链球菌生长影响的体外研究

目的研究酸性环境中甘草酸对体外培养变异链球菌生长的影响。方法在pH 7.0、pH 5.5和pH 4.0环境中培养变异链球菌，同时在培养基中加入3种浓度（0.78、1.57、3.13 mg·mL-1）的甘草酸，37 ℃下厌氧培养24 h后，测定各组的菌落计数和菌悬液吸光度值，分别以阴性对照组和pH 7.0组细菌生存率为对照，计算各组细菌的生存率。结果以阴性对照组为对照，0.78、1.57和3.13 mg·mL-1甘草酸组在pH 5.5环境时细菌生存率为60.96%、60.27%和45.58%，在pH 4.0时细菌生存率为68.75%、53.12%和45.83%。以pH 7.0组为对照，0.78、1.57和3.13 mg·mL-1甘草酸组在pH 5.5和pH 4.0时细菌生存率分别为52.25%和39.05%、74.39%和43.11%、86.38%和55.30%。结论在酸性环境中，甘草酸能够抑制体外变异链球菌的生长，环境酸度降低可使甘草酸的抑菌作用增强。

Effect of glycyrrhizic acid on growth of Streptococcus mutans under acid environment in vitro

Objective To investigate the antibacterial activity of glycyrrhizic acid（GA） against Streptococcus mutans （S. mutans） under acidic environment in vitro. Methods Working culture were prepared by inoculation of S. mutans into TPY broth followed by static incubation under anaerobic condition at 37 ℃ for 24 h. TPY broth was supplemented with three kinds density of GA（0.78, 1.57, 3.13 mg·mL-1）, whose acidity was regulated to pH 7.0, pH 5.5 and pH 4.0. And the group of pH 7.0 was used as negative control. The growth of S. mutans was measured by A600 of bacteria suspension and counting colony forming unit（CFU）. In addition, the survival rate of S. mutans was calculated. Results In pH 5.5 groups, the survival rates of 0.78, 1.57 and 3.13 mg·mL-1 GA groups were 60.96%, 60.27% and 45.58%, respectively, and in pH 4.0 groups, the survival rates were 68.75%, 53.12% and 45.83%. In 0.78, 1.57 and 3.13 mg·mL-1 GA groups, the survival rates of pH 5.5 and pH 4.0 were 52.25% and 39.05%, 74.39% and 43.11%, 86.38% and 55.30%, respectively. Conclusion GA could inhibit the gro wth of S.mutans under acidic environment, which the effect is improved as the acidity increased.