Effects of xylitol and fluoride on the response to glucose pulses of Streptococcus mutans T8 growing in continuous culture

Streptococcus mutans T8 was grown glucose-limited at pH 7.0 in a chemostat and pulsed, under pH free-fall conditions, with glucose, xylitol or a mixture of the two. Experiments were conducted in the absence or continual presence of low levels (1 mmol.l-1) of fluoride. Culture filtrates of samples taken at frequent intervals were assayed for carbohydrate and fermentation end-products. Fluoride had little effect on the organism's response to glucose until the culture pH fell to ca. 5.0, at which point the rate of lactate production was reduced some 3-fold. Xylitol affected the response to glucose but its effect was most marked in the presence of fluoride. Under these conditions, the rate of lactate production was reduced at least 3-fold, the pH did not fall to 5.0 and only about 50% of the added glucose was consumed. This suggests that xylitol can augment the metabolic effects on S. mutans of low levels of fluoride.     

Early childhood caries — a synopsis

All the papers presented at the conference are reviewed and comparisons are made with past beliefs on the topic. Early childhood caries (ECC) is a serious public health problem in disadvantaged communities in both developing and industrialized countries in which under-nutrition is common. ECC involves the maxillary primary incisors within months after their eruption and spreads rapidly to involve other primary teeth. The early implantation of mutans streptococci, the use of a feeding bottle containing sugary solutions and prolonged breast-feeding, especially at night, are important predisposing factors. Attention is drawn to the need for more research into the factors which determine the resistance of the enamel and particularly the elucidation of the relationship established in several countries between early enamel caries, enamel hypoplasia, and perinatal under- or malnutrition. Primary preventive measures should be applied during the ante- and immediate post-natal periods. Secondary preventive measures include the use of chemotherapeutic agents such as fluoride, and antimicrobials. The most appropriate tertiary preventive measure is the atraumatic restorative technique (ART). Broadly based committees should be established by governments to address the issues of caries risk in young children. Parents and all personnel involved in infant health and welfare should be shown how to recognize early signs of the condition, as well as to promote early intervention and referral.     

Identification of human antigenic epitopes in an alanine-rich repeating region using sera from hu-PBL-SCID mice immunized with a surface protein antigen of Streptococcus mutans

A 190-kDa surface protein antigen (PAc) of Streptococcus mutans is considered to play an important role in dental caries. To identify antigenic epitopes of the PAc in humans, we immunized severe combined immunodeficient (SCID) mice with re-combinant PAc that was transplanted with human peripheral blood mononuclear cells (PBMC). The reactivities of the sera from the immunized hu-PBL-SCID mice to the recombinant PAc and 24 19-mer synthetic peptides covering the alanine-rich repeating region (A-region) presented in the PAc molecule were then examined. The results showed that the immunized mice produced a significant recombinant PAc-specific human antibody, and among 24 19-mer peptides, 6 19-mer peptides showed a strong reaction with the antibodies. In addition, 4 19-mer peptides containing human antigenic epitope in a donor were identified with enzyme-linked immunosorbent assay (ELISA) inhibition assays using the recombinant PAc protein. In this study, the SCID mouse was useful in identifying human antigenic epitopes.     

Comparative analysis of the antibacterial effects of combined mouthrinses on Streptococcus mutans

BACKGROUND/AIMS: Chlorhexidine has been proposed as a potent chemotherapeutic agent against oral bacteria. However, there are some inconsistent results regarding the usefulness of chlorhexidine mouthrinse as an antimicrobial for Streptococcus mutans. The purpose of this study was to investigate the effectiveness of combining oral rinses to reduce S. mutans levels in human saliva. METHODS: Sixteen healthy adult subjects were randomly assigned to one of four rinse groups using a 4-cell crossover design. The groups rinsed twice a day for 7 days with one of the following: 0.12% chlorhexidine (PerioGard), 1.5% hydrogen peroxide (Peroxyl), a combined chlorhexidine+hydrogen peroxide, or water (control). Every 5 weeks, each group initiated a different rinse. Saline wash samples were collected on days 7 and 21 for assessment of S. mutans and total streptococci. RESULTS: No significant differences were seen in S. mutans levels among the groups; however, the levels of total streptococci on day 7 samples were significantly lower in the chlorhexidine and chlorhexidine+hydrogen peroxide groups than in the hydrogen peroxide and control groups. There was no additional decrease seen in S. mutans or total streptococci levels in the group receiving chlorhexidine+hydrogen peroxide compared to chlorhexidine alone. CONCLUSIONS: Sample variation was high throughout the study, with a significant trend toward lower counts as the study progressed. Adding hydrogen peroxide to the chlorhexidine mouthrinse did not result in a further decrease in S. mutans levels.     

Plasminogen interaction and activation on Streptococcus mutans surface

A number of pathogenic microorganisms have been previously shown to bind plasminogen. The subsequent activation of plasminogen into plasmin can contribute to their virulence. In this study, we have shown that Streptococcus mutans is able to bind both human plasminogen and plasmin. Binding of plasminogen to S. mutans was inhibited by L-lysine and epsilon-aminocaproic acid, indicating that binding is mediated via lysine-binding sites of plasminogen. S. mutans enhanced the activation of plasminogen by tissue plasminogen activator but not by urokinase. This enhancement turned out to be dependent on cell concentration. Zymogram analysis showed that the plasmin activity acquired after plasminogen binding and activation is the most important proteolytic activity in the strain tested. These results suggest a mechanism involving acquisition of a host protease that might contribute to the infective process of this microorganism.     

某健齿露防龋功能性评价的实验研究

目的　评价某健齿露对龋齿的预防作用。方法　离体试验 :将一定浓度的样品加入变形链球菌培养管中 ,培养一定时间 ,经革兰氏阳性染色和分光光度计测量观察变形链球菌的生长情况 ,测定其百分粘附率 ,并用酸度计测定细菌产酸后pH值。动物试验 :采用变形链球菌建立大鼠龋损模型 ,设立空白对照组 ,低、中、高三个剂量组 ,每日给样 ,连续 4 0天后处理动物 ,观察各组大鼠磨牙患龋情况 ,参照keyes经典龋齿计分标准进行龋齿计分。结果　变形链球菌生长正常 ,但易形成长链 ,粘附率降低。pH值升高 ,大于 6。动物实验表明 :实验组与对照组龋损程度、龋齿计分之间差异有显著性 (P <0 0 1)。结论　该样品能减少龋损的形成 ,有效降低大鼠龋病的发生、发展 ,有一定的防龋功能。其防龋机理在于该样品可促进变形链球菌凝集 ,抑制变形链球菌在玻璃上的粘附 ,降低变形链球菌产酸。     

载银纳米二氧化钛义齿基托的体外抗菌实验研究

目的研究加入载银纳米二氧化钛抗菌粉的聚甲基丙烯酸甲酯义齿基托体外对口腔常见致病菌(变形链球菌)的抗菌效果。方法测定载银纳米二氧化钛抗菌粉对变形链球菌的最小抑菌浓度,并以此为依据,在义齿基托中添加载银纳米二氧化钛抗菌粉,观察加入不同浓度载银纳米二氧化钛抗菌粉的义齿基托对变形链球菌的抗菌效果。结果载银纳米二氧化钛抗菌粉对变形链球菌的最小抑菌浓度为2.5g/L;当载银纳米二氧化钛抗菌粉在树脂基托中的浓度为1.25、2.5、5.0、10.0g/L时,其对变形链球菌抗菌率达分别为75.3%、89.9%、95.4%、99.9%。结论加入载银纳米二氧化钛抗菌粉的义齿基托在体外对变形链球菌具有良好的抗菌效果,能够达到义齿在口腔中的抗菌要求。     

Current status of a mucosal vaccine against dental caries

The evidence of a specific bacterial cause of dental caries and of the function of the salivary glands as an effector site of the mucosal immune system has provided a scientific basis for the development of a vaccine against this highly prevalent and costly oral disease. Research efforts towards developing an effective and safe caries vaccine have been facilitated by progress in molecular biology, with the cloning and functional characterization of virulence factors from mutans streptococci, the principal causative agent of dental caries, and advancements in mucosal immunology, including the development of sophisticated antigen delivery systems and adjuvants that stimulate the induction of salivary immunoglobulin A antibody responses. Cell-surface fibrillar proteins, which mediate adherence to the salivary pellicle, and glucosyltransferase enzymes, which synthesize adhesive glucans and allow microbial accumulation, are virulence components of mutans streptococci, and primary candidates for a human caries vaccine. Infants, representing the primary target population for a caries vaccine, become mucosally immunocompetent and secrete salivary immunoglobulin A antibodies during the first weeks after birth, whereas mutans streptococci colonize the tooth surfaces at a discrete time period that extends around 26 months of life. Therefore, immunization when infants are about one year old may establish effective immunity against an ensuing colonization attempts by mutans streptococci. The present review critically evaluates recent progress in this field of dental research and attempts to stress the protective potential as well as limitations of caries immunization.     

In vitro antimicrobial activity of a chitooligosaccharide mixture against Actinobacillus actinomycetemcomitans and Streptococcus mutans.

The purpose of this study was to evaluate the in vitro antibacterial activity of a chitooligosaccharide mixture (MW 2000–30 000 Da) with a deacetylation degree of 91.5% against two representative oral pathogens, Actinobacillus actinomycetemcomitans and Streptococcus mutans. A 0.1% concentration of the chitooligosaccharides (derived from the exoskeletons of marine crustaceans) was used to estimate antibacterial activity. Approximately 2 log colony forming units (CFU)/ml of A. actinomycetemcomitans were inactivated by 0.1% chitosan after 30 min, while 120 min exposure inactivated about 4.5 log CFU/ml of this organism. In contrast, the level of inactivation against S. mutans was less than 0.5 log CFU/ml after an exposure of up to 120 min. Electron microscopy showed that the exposure of A. actinomycetemcomitans to the chitooligosaccharides resulted in the disruption of cell membranes and that it could be considered for the treatment of periodontal diseases associated with A. actinomycetemcomitans.     

A longitudinal study of dental caries risk among very young low SES children

Abstract – Objectives: Early childhood caries (ECC) is a challenging public health problem in the United States and elsewhere; however, there is limited information concerning risk factors in very young children. The purpose of this study was to assess baseline risk factors for 18‐month caries prevalence as part of a longitudinal study of high‐risk children. Methods: About 212 children, 6–24 months of age were recruited from a rural community in Iowa. Subjects were enrolled in the WIC program, which provides nutritional support for low‐income families with children. Dental examinations using d1, d2–3 criteria were conducted at baseline and after 18 months. Caries prevalence was determined at the frank decay level (d2–3 or filled surfaces), as well as at the noncavitated level (d1), and combined (d1, d2–3 or f surfaces). Risk factor data were collected at baseline and after 9‐ and 18‐ months. These data included beverage consumption data, presence of visible plaque, and use of fluoride toothpaste for children as well as mutans streptococci (MS) levels of mothers and children and family sociodemographic factors. Results: About 128 children (60%) remained in the study after 18 months. Among these children, prevalence of d1,d2–3/f level caries increased from 9% to 77%, while d2–3/f level caries increased from 2% to 20%. Logistic regression models for baseline predictors of d2–3f caries at the 18‐month follow‐up found the presence of MS in children (OR = 4.4; 95% CI: 1.4, 13.9) and sugar‐sweetened beverages (OR = 3.0; 95% CI: 1.1, 8.6) to be the only significant risk factors. Sociodemographic factors and the use of fluoride toothpaste were not significant in these models. Conclusions: Results suggest that early colonization by MS and consumption of sugar‐sweetened beverages are significant predictors of ECC in high‐risk populations.