Department of Preventive and Restorative Dentistry, School of Dentistry, São Paulo State University (UNESP), Araçatuba, SP, Brazil; Centro Universitário São Lucas, Porto Velho, RO, Brazil.
Department of Preventive and Restorative Dentistry, School of Dentistry, São Paulo State University (UNESP), Araçatuba, SP, Brazil.
Microb Pathog. 2021 Jan;150:104669. doi: 10.1016/j.micpath.2020.104669. Epub 2020 Dec 2.
Streptococcus mutans is the main etiological agent of dental caries because of its capacity to adhere to enamel structure and form biofilms. This study aimed to evaluate the effects of the anticariogenic agents - sodium fluoride (NaF) and chlorhexidine (CHX) - at levels below minimum inhibitory concentrations (sub-MICs) on the growth of planktonic cells and biofilms and on the expression of vicR and covR genes associated with the regulation of biofilm formation. MICs and minimum bactericidal concentrations (MBCs) of NaF and CHX were determined for S. mutans strains ATCC25175, UA159 and 3VF2. Growth curves were constructed for planktonic cells cultured in brain heart infusion (BHI) broth supplemented with NaF (0.125-0.75MIC) or CHX (0.25-0.75MIC). Biofilm formation assays were performed in microplates containing CHX or NaF at 0.5-1.0MIC and stained with violet crystal. Quantitative polymerase chain reaction determined the alterations in covR and vicR expression in cells exposed to antimicrobials at sub-MIC levels. NaF and CHX at sub-MIC levels affected the growth of planktonic cells of all three S. mutans strains, depending on the concentration tested. The biofilm formation in UA159 and 3VF2 was reduced by NaF at concentrations ≥0.5 MIC, while that of ATCC 25175 was reduced significantly irrespective of dose. In contrast, UA159 and 3VF2 biofilms were not affected by CHX at these levels, whereas those of ATCC 25175 were reduced significantly at all concentrations tested. Under sub-MIC conditions, CHX and (to a lesser degree) NaF increased vicR and covR expression in all three strains, although there were large differences between strains and treatment conditions employed. CHX and NaF at sub-MIC levels influence on the growth of S. mutans in planktonic and biofilm conditions and on transcript levels of biofilm-associated genes vicR and covR, in a dose-dependent manner.
变形链球菌是龋齿的主要病因，因为它能够附着在釉质结构上并形成生物膜。本研究旨在评估抗龋剂-氟化钠（NaF）和洗必泰（CHX）在低于最低抑菌浓度（sub-MIC）水平下对浮游细胞和生物膜生长以及与生物膜形成调节相关的 vicR 和 covR 基因表达的影响。测定了 S. mutans 菌株 ATCC25175、UA159 和 3VF2 的 NaF 和 CHX 的 MIC 和最低杀菌浓度（MBC）。构建了在添加 NaF（0.125-0.75MIC）或 CHX（0.25-0.75MIC）的脑心浸液（BHI）肉汤中培养的浮游细胞生长曲线。在含有 0.5-1.0MIC 的 CHX 或 NaF 的微孔板中进行生物膜形成测定，并使用紫晶染色。定量聚合酶链反应确定了在 sub-MIC 水平下暴露于抗菌剂的细胞中 covR 和 vicR 表达的变化。NaF 和 CHX 在 sub-MIC 水平上影响所有三种 S. mutans 菌株的浮游细胞生长，这取决于测试的浓度。在浓度≥0.5MIC 时，NaF 降低了 UA159 和 3VF2 的生物膜形成，而 ATCC 25175 的生物膜形成则显著降低，而与剂量无关。相比之下，在这些水平下，CHX 对 UA159 和 3VF2 生物膜没有影响，而在所有测试浓度下，ATCC 25175 的生物膜均显著降低。在 sub-MIC 条件下，CHX 和（在较小程度上）NaF 增加了所有三种菌株的 vicR 和 covR 表达，尽管菌株之间和处理条件之间存在很大差异。CHX 和 NaF 在 sub-MIC 水平上以剂量依赖的方式影响浮游和生物膜条件下 S. mutans 的生长以及与生物膜相关的基因 vicR 和 covR 的转录水平。
