Streptococcus mutans is a major cause of tooth decay due to its promotion of biofilm formation and acid production. Several plant extracts have been reported to have multiple biological activities such as anti‐inflammation and antibacterial effects. This study investigated the antibacterial activity of three plant extracts, phellodendron bark (PB), yucca, and black ginger, and found that PB had a stronger effect than the other extracts. Then, the minimum inhibitory concentration (MIC) of PB against 100 S. mutans strains was investigated. The MIC range of PB was 9.8–312.5 µg/mL. PB suppressed the growth kinetics of S. mutans in a dose‐dependent manner, even at sub‐MICs of PB. Then, we investigated the effect of PB on S. mutans virulence. The PB suppressed biofilm formation at high concentrations, although PB did not affect the expression of glucosyltransferase genes. Additionally, PB suppressed the decrease in pH from adding an excess of glucose. The expression of genes responsible for acid production was increased by the addition of excess glucose without PB, whereas their expression levels were not increased in the presence of 1× and 2× MIC of PB. Although PB showed a bacteriostatic effect on planktonic S. mutans cells, it was found that more than 2× MIC of PB showed a partial bactericidal effect on biofilm cells. In conclusion, PB not only showed antibacterial activity against S. mutans but also decreased the cariogenic activity in S. mutans .

中文翻译：

---

黄柏树皮对变形链球菌的抗菌活性。

变形链球菌由于其促进生物膜形成和产酸而成为蛀牙的主要原因。据报道，几种植物提取物具有多种生物活性，例如抗炎和抗菌作用。这项研究调查了三种植物提取物，黄柏树皮（PB），丝兰和黑姜的抗菌活性，发现PB具有比其他提取物更强的抗菌作用。然后，研究了PB对100株变形链球菌菌株的最小抑制浓度（MIC）。PB的MIC范围为9.8-312.5 µg / mL。PB即使在PB的亚MIC下也以剂量依赖的方式抑制变形链球菌的生长动力学。然后，我们研究了PB对变形链球菌的影响毒力。PB在高浓度下抑制了生物膜的形成，尽管PB不影响葡萄糖基转移酶基因的表达。另外，PB通过添加过量的葡萄糖抑制了pH的降低。通过添加过量的葡萄糖而不添加PB来增加负责酸产生的基因的表达，而在PB的1x和2x MIC存在下它们的表达水平没有增加。尽管PB对浮游变形链球菌具有抑菌作用，但发现PB的MIC大于2倍对生物被膜细胞具有部分杀菌作用。总之，PB不仅表现出对抗菌活性变形链球菌，但也减少致龋活动变形链球菌。