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目的了解变异链球菌(简称变链菌)593号高致龋力临床分离株在生物膜状态不同时期与标准株ATCC25175(均为血清型c)合成胞外多糖的能力差异。方法在聚苯乙烯塑料片上分别形成3、12、20 h变链菌生物膜标本,采用异硫氰酸荧光素标记的伴刀豆球蛋白A对合成的胞外多糖进行染色,用激光共聚焦扫描显微镜(CLSM)观察。采用静置法培养形成黏附生长的细菌,蒽酮法测定3～24 h其合成胞外多糖的量。结果胞外多糖与染料结合后发出绿色荧光,各时间段593号临床株绿色荧光的分布较ATCC 25175标准株更致密和广泛。3～20 h 593号临床株合成水溶性葡聚糖能力强于标准株(P<0.05);3～16 h 593号临床株合成水不溶性葡聚糖能力强于标准株(P<0.05);其他时间两者合成胞外多糖的能力差异无统计学意义(P>0.05)。结论在生物膜形成过程中两菌株合成胞外多糖的模式相同,均随时间延长而合成量增加,但在生物膜形成早期(3～16 h)高致龋力临床株表现出不同于标准株的胞外多糖合成模式,其更强的合成胞外多糖能力可能是其具高致龋力的原因之一,提示研究致龋机制时使用临床株作为研究样本较标准株更为敏感。
OBJECTIVE: To investigate the differences in the ability of extracellular polysaccharide of Streptococcus mutans (593) isolating cariogenic clinical isolates from the standard strain ATCC25175 (all of serotype c) at different stages of biofilm status. Methods Streptococcus mutans biofilm samples were obtained on 3, 3, 20, 20 h plastic polystyrene flakes. The synthesized polysaccharide was stained with fluorescein isothiocyanate labeled concanavalin A. The confocal laser scanning microscopy Scanning microscopy (CLSM) observation. Anthrone method was used to measure the amount of extracellular polysaccharides produced during the period of 3 ~ 24 h. Results The exopolysaccharides released green fluorescence when combined with the dye. The distribution of green fluorescence of clinical strain 593 in each time period was more dense and extensive than that of ATCC 25175 standard strain. The capacity of synthesizing water-soluble dextran from 593 clinical strains was higher than that of the standard strains (P <0.05) at 3 ~ 20 h and that of 593 clinical strains at 3 ~ 16 h was stronger than that of the standard strain (P <0.05). There was no significant difference in the ability to synthesize exopolysaccharides at other times (P> 0.05). Conclusion The biosynthesis of exopolysaccharides in the two biofilms during the biofilm formation process are the same, both of which increase with time. However, in the early stage of biofilm formation (3 ~ 16 h), the cariogenic clinical isolates showed different from the standard strains Of the extracellular polysaccharide synthesis mode, the stronger ability of the synthesis of exopolysaccharides may be one of the causes of its high cariogenic strength, suggesting that the use of clinical strains as a study sample when caries-causing mechanisms are more sensitive than the standard strains.