Tea extracts inhibit the attachment of streptococci to oral/dental substrata by reducing hydrogen bonding energies

Previous work in the authors’ lab demonstrated that tea extracts significantly suppressed streptococcal colonization of abiotic substrata by coating the bacterial cell surfaces with tea components. In this study, the physico-chemical mechanisms by which the tea coating inhibits cellular attachment are demonstrated. The changes in the cell surface physico-chemical properties of streptococci, induced by tea extracts, were measured. Using these results, surface interaction energies were calculated between streptococcal cells and hard surfaces (glass, stainless steel, hydroxyapatite and titanium) within the cellular attachment system exploiting the extended Derjaguin-Landau-Verwey-Overbeek theory. The net energy outcomes were compared with experiment results of attachment assays to validate the predictability of the model. The results showed that the tea extracts inhibited the attachment of the bacteria by 11.1%–91.5%, and reduced the interaction energy by 15.4%–94.9%. It was also demonstrated that the abilities of the bacteria to attach to hard surfaces correlated well with their net interaction energies. The predominant interaction in the systems was found to be hydrogen bonding. In conclusion, tea extracts suppress streptococcal attachment to hard substrata by limiting the formation of hydrogen bonds.

作者所在实验室的前期研究表明，茶叶提取物可通过在细菌细胞表面包覆茶叶成分，显著抑制链球菌在非生物基质上的定殖。本研究阐明了茶叶包覆层抑制细菌细胞黏附的物理化学机制：研究人员测定了茶叶提取物诱导下链球菌细胞表面物理化学性质的变化。基于上述测定结果，本研究利用扩展德根-朗道-韦弗-奥弗比克（Derjaguin-Landau-Verwey-Overbeek）理论，计算了细菌黏附体系中链球菌细胞与硬表面（玻璃、不锈钢、羟基磷灰石（hydroxyapatite）和钛（titanium））之间的表面相互作用能。将计算得到的净相互作用能结果与黏附实验的实测结果进行对比，以验证该模型的预测能力。结果显示，茶叶提取物可使细菌黏附率降低11.1%~91.5%，同时使表面相互作用能降低15.4%~94.9%。研究同时证实，细菌在硬表面的黏附能力与其净相互作用能具有显著相关性。该体系中的主导相互作用为氢键作用。综上，茶叶提取物可通过抑制氢键的形成，减少链球菌在硬基质表面的黏附。