Quaternary ammonium-induced multidrug tolerant Streptococcus mutans persisters elevate cariogenic virulence in vitro.

Dental caries are the most prevalent chronic infections in the oral cavity, and Streptococcus mutans acts as the main cariogenic bacterial species. Antibacterial quaternary ammonium compounds (QAs) have been developed to preveFnt or treat dental caries. However, there is no report on the tolerance of S. mutans to QAs. In this study, we investigated the development of S. mutans persistence induced by a novel dental caries defensive agent, dimethylaminododecyl methacrylate (DMADDM), for the first time. Typical biphasic killing kinetics for persisters were observed in both S. mutans planktonic and biofilm cultures challenged by DMADDM at concentrations of 20 and 200 µg·mL-1, respectively. The persisters tolerated six other antibiotics with different antibacterial mechanisms, while only daptomycin and vancomycin could slightly reduce the persister numbers in planktonic cultures. The distribution of persisters in DMADDM-treated biofilms was similar to that in the untreated control, except that the total biomass and biofilm height were significantly reduced. A higher exopolysaccharides (EPS):bacteria ratio was observed in DMADDM-treated biofilms. Persisters in biofilms significantly upregulated gtf gene expression, indicating an increase in the bacteria's ability to produce EPS and an elevated capability of cariogenic virulence. Carbon source metabolism was significantly reduced, as related metabolic genes were all downregulated in persisters. Concentrations of 0.1 mM, 1 mM and 10 mM of extra glucose significantly reduced the number of persisters both in planktonic and biofilm conditions. The formation of non-inheritable and multidrug tolerant persisters induced by DMADDM suggested that drug tolerance and new persistent eradication strategies should be considered for oral antibacterial agents.

[Effects of vinegar on tooth bleaching and dental hard tissues in vitro].

OBJECTIVE: To determine the effects of three acidoid bleaching agents on tooth color and dental hard tissues. METHODS: Bovine tooth blocks with 5 mm x 3 mm enamel surface exposure were randomly divided into four groups: white vinegar group (group A),apple vinegar group (group B), 30% hydrogen peroxid group (group C) and deionized water (group D), each containing ninety blocks. In each group, the tooth blocks were further equally divided into three sub groups, exposing to their respective bleaching agents for 30 s, 1 min and 3 min, respectively. The experiment was performed under simulated oral environment. The changes in color,microhardness and morphological characteristics of the tooth blocks were tested by ShadeEye NCC,microhardness tester and SEM. RESULTS: Tooth blocks exposed to white vinegar had the most notable decrease in hardness, changes in color and morphological characteristics enamel surface. CONCLUSION: White vinegar, apple vinegar and hydrogen peroxidhave bleaching effects on teeth, but white vinegar may causehigher levels of damage to the hardness and surface configuration of teeth.