Department of Pediatric Dentistry, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
Microbiol Immunol. 2020 Jun;64(6):424-434. doi: 10.1111/1348-0421.12787. Epub 2020 Apr 23.
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.
变形链球菌是导致龋齿的主要原因，因为它促进了生物膜的形成和酸的产生。已经有报道称，几种植物提取物具有多种生物活性，如抗炎和抗菌作用。本研究调查了三种植物提取物黄柏、丝兰和黑姜的抗菌活性，发现黄柏的作用比其他提取物更强。然后，研究了黄柏对 100 株变形链球菌的最小抑菌浓度（MIC）。黄柏的 MIC 范围为 9.8-312.5μg/ml。黄柏以剂量依赖的方式抑制变形链球菌的生长动力学，即使在黄柏的亚 MIC 下也是如此。然后，我们研究了黄柏对变形链球菌毒力的影响。黄柏在高浓度下抑制生物膜的形成，尽管黄柏不影响葡糖基转移酶基因的表达。此外，黄柏抑制了因添加过量葡萄糖而导致的 pH 值下降。在没有黄柏的情况下，过量葡萄糖的添加会增加负责产酸的基因的表达，但在黄柏的 1×和 2× MIC 存在下，其表达水平没有增加。虽然黄柏对浮游变形链球菌细胞表现出抑菌作用，但发现黄柏的 MIC 超过 2×倍时对生物膜细胞表现出部分杀菌作用。总之，黄柏不仅对变形链球菌表现出抗菌活性，而且降低了变形链球菌的致龋活性。
