不同pH对变异链球菌体外生物膜形成的影响

目的：了解变异链球菌临床株体外生物膜形成规律以及不同pH对生物膜形成的影响。方法：采用微孔板培养,染色、分光光度测定法（A630）绘制体外不同pH条件下（pH=7.0～5.0）593号、18号菌株以及变异链球菌标准株（ATCC25175）的生物膜生长曲线。结果：体外变异链球菌各株在pH=5.0时均不能形成生物膜;pH=7.0时细菌生物膜形成表现为缓慢的非线性生长,12～24h生物膜开始成熟,24～36h出现一相对的生长停滞期;pH=5.0时对已形成12h的变链菌生物膜生长有明显的抑制作用,但经历12h的酸休克后各菌株的生物膜均能恢复生长。结论：变异链球菌在体外pH=7.0时于12～24h形成稳定的生物膜,该生物膜能抵抗一定程度的酸（pH=5.0）攻击,而浮游状态的细菌则不能。

Effect of different pH on Streptococcus mutans biofilm formation in vitro

Objective：To learn the pattern of biofilm formation and the different pH effect of clinical S. mutans biofilm formation. Method：Biofilm growth curve of 593、18 strains and the standard strain（ATCC 25175）under different pH conditions （pH=7.0～5.0）was drawn by means of the microplate cultivate,dyeing and spectrophotometry （A630）. Result： There was no biofilm formation in various strains in vitro at pH=5.0. Slow non-linear growth of bacterial biofilm was observed at pH=7.0. Biofilm became mature about 12～24h. There was a relative stagnation period of the growth between 24～36 h. The growth of S. mutans biofilm formed after 12 h was inhibited obviously at pH=5.0. However,all biofilms were able to restore growth after the acid shock at 12 h. Conclusion：In vitro S. mutans form a stable biofilm during 12～24 h at pH=7.0, which can resistant a certain degree of acid（pH=5.0）attack. However,planktonic bacteria can not risist the attack.