State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Dept. of Cariology and Endodonics West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
Department of Advanced Oral Sciences & Therapeutics, University of Maryland Dental School, Baltimore, MD, 21201, USA.
J Mater Sci Mater Med. 2017 Oct 4;28(11):178. doi: 10.1007/s10856-017-5981-9.
Antibacterial monomers can combat oral biofilm acids and caries; however, little is known on whether quaternary ammonium monomers (QAMs) would induce drug persistence in oral bacteria. The objectives of this study were to investigate the interactions of Streptococcus mutans (S. mutans) with dimethylaminohexadecyl methacrylate (DMAHDM), and determine for the first time whether DMAHDM could induce persisters in S. mutans. DMAHDM was synthesized using a modified Menschutkin reaction. Dose-dependent killing curves and time-dependent killing curves of planktonic S. mutans and biofilms were determined to evaluate drug persistence, using chlorhexidine (CHX) as control. The inheritability assay, minimum inhibitory concentration (MIC) and live/dead biofilm assay were determined to investigate persister characteristics. DMAHDM matched the killing potency of the gold standard CHX against S. mutans biofilms. DMAHDM and CHX induced drug persistence in S. mutans biofilms but not in planktonic bacteria. S. mutans biofilm persistence was not inheritable in that the tolerance to DMAHDM or CHX of the surviving persisters in the initial population was not transferred to subsequent generations, as displayed by the inheritability assay. The MIC of S. mutans parental strain and induced persisters remained the same. The induced persisters in S. mutans biofilms could be eliminated via higher doses of 300 μg/mL of DMAHDM and CHX. In conclusion, this study showed for the first time that (1) DMAHDM induced persisters only in biofilms, but not in planktonic bacteria; and (2) both DMAHDM-induced and CHX-induced S. mutans persister biofilms could be completely eradicated by even higher concentrations of DMAHDM and CHX. More studies are needed on the induction of persisters in oral biofilms for the development and use of a new generation of antibacterial dental monomers and resins.
抗菌单体可以对抗口腔生物膜酸和龋齿；然而，对于季铵单体（QAMs）是否会导致口腔细菌产生药物持久性，目前知之甚少。本研究的目的是研究变形链球菌（S. mutans）与二甲氨基十六烷基甲基丙烯酸酯（DMAHDM）的相互作用，并首次确定 DMAHDM 是否会诱导 S. mutans 产生持续存在的细菌。DMAHDM 是通过改良的曼希特金反应合成的。使用氯己定（CHX）作为对照，通过测定浮游 S. mutans 和生物膜的剂量依赖性杀伤曲线和时间依赖性杀伤曲线，评估药物持久性。通过遗传实验、最小抑菌浓度（MIC）和死活生物膜实验，研究持久性特征。DMAHDM 对 S. mutans 生物膜的杀伤效力与金标准 CHX 相当。DMAHDM 和 CHX 诱导 S. mutans 生物膜产生药物持久性，但不诱导浮游细菌产生药物持久性。在遗传实验中，初始种群中存活的持续存在菌对 DMAHDM 或 CHX 的耐受性没有传递给后代，表明 S. mutans 生物膜持久性不是可遗传的。S. mutans 亲本菌株和诱导的持续存在菌的 MIC 保持不变。通过使用更高剂量的 300μg/mL DMAHDM 和 CHX，可以消除 S. mutans 生物膜中的诱导持续存在菌。总之，本研究首次表明：（1）DMAHDM 仅在生物膜中诱导持续存在菌，而不在浮游细菌中诱导；（2）DMAHDM 诱导和 CHX 诱导的 S. mutans 持续存在菌生物膜可以通过更高浓度的 DMAHDM 和 CHX 完全消除。为了开发和使用新一代抗菌牙科单体和树脂，需要对口腔生物膜中持续存在菌的诱导进行更多研究。
