Streptococcus mutans: fructose transport, xylitol resistance, and virulence

Gene expression and metabolic activity of Streptococcus mutans during exposure to dietary carbohydrates glucose, sucrose, lactose, and xylitol

Recent RNA sequencing studies have given us a deeper insight into the cariogenic impact of carbohydrate sources in the bacterium Streptococcus mutans, the principal microbial agent in dental caries etiopathogenesis. The process of dental caries development is facilitated by the ability of this bacterium to ferment some carbohydrates into organic acids contributing to a pH decrease in the oral cavity and the demineralization of the hard tissues of the tooth. Furthermore, in dental caries progression, biofilm formation, which starts and ends with free planktonic cells, plays an important role and has several unique properties called virulence factors. The most cariogenic carbohydrate is sucrose, an easily metabolizable source of energy that induces the acidification and synthesis of glucans, forming typical bacterial cell clumps. We used multifaceted methodological approaches to compare the transcriptomic and metabolomic profiles of S. mutans growing in planktonic culture on preferred and nonpreferred carbohydrates and in fasting conditions. Streptococcus mutans in a planktonic culture with lactose produced the same pH drop as glucose and sucrose. By contrast, xylitol and lactose showed high effectiveness in regulating intracellular polysaccharide metabolism, cell wall structure, and overall virulence involved in the initial phase of biofilm formation and structure but with an opposite pattern compared with sucrose and glucose. Our results confirmed the recent findings that xylitol and lactose play a vital role in biofilm structure. However, they do not reduce its formation, which is related to the creation of a cariogenic environment.

Murine Salivary Amylase Protects Against Streptococcus mutans-Induced Caries

Saliva protects dental surfaces against cavities (i. e., dental caries), a highly prevalent infectious disease frequently associated with acidogenic Streptococcus mutans. Substantial in vitro evidence supports amylase, a major constituent of saliva, as either protective against caries or supporting caries. We therefore produced mice with targeted deletion of salivary amylase (Amy1) and determined the impact on caries in mice challenged with S. mutans and fed a diet rich in sucrose to promote caries. Total smooth surface and sulcal caries were 2.35-fold and 1.79-fold greater in knockout mice, respectively, plus caries severities were twofold or greater on sulcal and smooth surfaces. In in vitro experiments with samples of whole stimulated saliva, amylase expression did not affect the adherence of S. mutans to saliva-coated hydroxyapatite and slightly increased its aggregation in solution (i.e., oral clearance). Conversely, S. mutans in biofilms formed in saliva with 1% glucose displayed no differences when cultured on polystyrene, but on hydroxyapatite was 40% less with amylase expression, suggesting that recognition by S. mutans of amylase bound to hydroxyapatite suppresses growth. However, this effect was overshadowed in vivo, as the recoveries of S. mutans from dental plaque were similar between both groups of mice, suggesting that amylase expression helps decrease plaque acids from S. mutans that dissolve dental enamel. With amylase deletion, commensal streptococcal species increased from ~75 to 90% of the total oral microbiota, suggesting that amylase may promote higher plaque pH by supporting colonization by base-producing oral commensals. Importantly, collective results indicate that amylase may serve as a biomarker of caries risk.

Activity of Ligustrum robustum (Roxb.) Blume extract against the biofilm formation and exopolysaccharide synthesis of Streptococcus mutans

Ligustrum robustum (Roxb.) Blume is utilized as a traditional Chinese herbal tea with various health benefits and protective effects. Streptococcus mutans is an important cariogenic oral bacteria species. The present study aimed to assess the influence of Ligustrum robustum extract (LRE) on the biofilm formation of S. mutans and the mechanism of its action, as well as to identify its chemical components. For chemical identification, HPLC-MS and nuclear magnetic resonance were applied and four identified phytochemicals were reported (Ligurobustoside B, Ligurobustoside N, Ligurobustoside J, and Ligurobustoside C). The dose-dependent (0.5 to 2.0 μg/μL) antimicrobial toxicity of LRE against S. mutans biofilm formation and exopolysaccharide (EPS) synthesis was evaluated by confocal laser scanning microscopy (CLSM), Crystal violet stain, and CFU counting. The microstructure of S. mutans biofilm treated with LRE was investigated both on glass coverslips and ex vivo bovine dental enamel by scanning electron microscopy (SEM). Moreover, LRE downregulated the expression of S. mutans glucosyltransferase-encoding genes gtfB, gtfC, and gtfD, and the quorum sensing (QS) factors comD and comE, suggesting its toxic mechanism. In addition, the result of CCK-8 test on human oral cells revealed an acceptable biocompatibility of LRE. These findings indicated the possible application of this daily consumed herbal tea for caries prevention.

Association between dental caries and adverse pregnancy outcomes

Poor oral health is not only associated with diabetes and cardiovascular disease but adverse pregnancy outcomes. However the influence of dental caries on pregnancy is unknown. The aim of this study was to evaluate the association between dental caries and adverse pregnancy outcomes and the effect of treatment for dental caries on adverse pregnancy outcomes. Primiparas who delivered a singleton between January 1, 2010 and December 31, 2014 and underwent both general health examination and oral health examination during a National Korea Health Screening Examination within 1 year of pregnancy were eligible. The data of the women who met the inclusion criteria were linked to the data of their offspring contained within the National Korea Health Screening Program for Infants and Children database. Among 120,622 women who delivered during the study period, 28,623 (23.7%) women had dental caries. Among them, 4,741 (16.6%) women were treated for dental caries after diagnosis. In a multivariable analysis, women with dental caries had an increased risk of delivering large-for-gestational-age infants (odds ratio, 1.15; 95% confidence interval, 1.07, 1.23) compared to those without dental caries. When women with dental caries were divided on the basis of the treatment of dental caries, women with dental caries but no treatment had an increased risk of delivering large-for-gestational-age infants (odds ratio, 1.15; 95% confidence interval, 1.06, 1.24); conversely, there was no increased risk in women with dental caries and treatment compared with those without. Dental caries and its treatment were not associated with preterm birth and preeclampsia. Untreated dental caries was not associated with preterm birth or preeclampsia but with the risk of delivering large-for-gestational-age infants. These whole observation may be attributed to the various characteristics of mothers who develop dental caries are not treated.

Essential Roles of the sppRA Fructose-Phosphate Phosphohydrolase Operon in Carbohydrate Metabolism and Virulence Expression by Streptococcus mutans

The dental caries pathogen Streptococcus mutans can ferment a variety of sugars to produce organic acids. Exposure of S. mutans to certain nonmetabolizable carbohydrates, such as xylitol, impairs growth and can cause cell death. Recently, the presence of a sugar-phosphate stress in S. mutans was demonstrated using a mutant lacking 1-phosphofructokinase (FruK) that accumulates fructose-1-phosphate (F-1-P). Here, we studied an operon in S. mutans, sppRA, which was highly expressed in the fruK mutant. Biochemical characterization of a recombinant SppA protein indicated that it possessed hexose-phosphate phosphohydrolase activity, with preferences for F-1-P and, to a lesser degree, fructose-6-phosphate (F-6-P). SppA activity was stimulated by Mg2+ and Mn2+ but inhibited by NaF. SppR, a DeoR family regulator, repressed the expression of the sppRA operon to minimum levels in the absence of the fructose-derived metabolite F-1-P and likely also F-6-P. The accumulation of F-1-P, as a result of growth on fructose, not only induced sppA expression, but it significantly altered biofilm maturation through increased cell lysis and enhanced extracellular DNA release. Constitutive expression of sppA, via a plasmid or by deleting sppR, greatly alleviated fructose-induced stress in a fruK mutant, enhanced resistance to xylitol, and reversed the effects of fructose on biofilm formation. Finally, by identifying three additional putative phosphatases that are capable of promoting sugar-phosphate tolerance, we show that S. mutans is capable of mounting a sugar-phosphate stress response by modulating the levels of certain glycolytic intermediates, functions that are interconnected with the ability of the organism to manifest key virulence behaviors.IMPORTANCEStreptococcus mutans is a major etiologic agent for dental caries, primarily due to its ability to form biofilms on the tooth surface and to convert carbohydrates into organic acids. We have discovered a two-gene operon in S. mutans that regulates fructose metabolism by controlling the levels of fructose-1-phosphate, a potential signaling compound that affects bacterial behaviors. With fructose becoming increasingly common and abundant in the human diet, we reveal the ways that fructose may alter bacterial development, stress tolerance, and microbial ecology in the oral cavity to promote oral diseases.

Xylitol and sorbitol effects on the microbiome of saliva and plaque

Chewing gum containing xylitol may help prevent caries by reducing levels of mutans streptococci (MS) and lactobacilli in saliva and plaque. Very little is known about other species which are possibly beneficial to oral health. In this study, we employed high-throughput sequencing of the 16S rRNA gene to profile microbial communities of saliva and plaque following short-term consumption of xylitol and sorbitol containing chewing gum. Participants (n = 30) underwent a washout period and were randomly assigned to one of two groups. Each group chewed either xylitol or sorbitol gum for three weeks, before undergoing a second four-week washout period after which they switched to the alternate gum for three weeks. Analysis of samples collected before and after each intervention identified distinct plaque and saliva microbial communities that altered dependent on the order in which gum treatments were given. Neither the xylitol nor sorbitol treatments significantly affected the bacterial composition of plaque. Lactobacilli were undetected and the number of Streptococcus mutans sequence reads was very low and unaffected by either xylitol or sorbitol. However, sorbitol affected several other streptococcal species in saliva including increasing the abundance of S. cristatus, an oral commensal shown to inhibit bacteria associated with chronic periodontitis.

Comparative evaluation of 0.2% Chlorhexidine Mouthwash, Xylitol Chewing Gum, and Combination of 0.2% Chlorhexidine Mouthwash and Xylitol Chewing Gum on Salivary Streptococcus mutans and Biofilm Levels in 8- to 12-Year-Old Children

AIM

To assess the effect of combining 0.2% chlorhexidine (CHX) mouthwash with xylitol (XYL) chewing gum on Streptococcus mutans and biofilm levels among 8- to 12-year-old children.

MATERIALS AND METHODS

Sixty children aged 8 to 12 years were selected with moderate and high salivary S. mutans levels. They were divided into three groups of 20 children each: (1) XYL group where the subjects chewed XYL twice daily; (2) CHX where rinsing was done twice daily; and (3) combination of XYL and CHX group (XYL+CHX) where both the agents were used once daily. The S. mutans colony-forming units (CFUs) were counted by using the mitis salivarius agar plate at the beginning of the study and at 15 days, 1, 2, and 6 months from the start of the study.

RESULTS

The XYL+CHX group showed the maximum reduction in both the biofilm and S. mutans scores throughout the study period.

CONCLUSION

The XYL+CHX combination reduced both the biofilm and S. mutans score significantly better than either XYL chewing gums or CHX mouthwash used alone.

HOW TO CITE THIS ARTICLE

Syed M, Chopra R, Shrivastava V, Sachdev V. Comparative evaluation of 0.2% Chlorhexidine Mouthwash, Xylitol Chewing Gum, and Combination of 0.2% Chlorhexidine Mouthwash and Xylitol Chewing Gum on Salivary Streptococcus mutans and Biofilm Levels in 8- to 12-Year-Old Children. Int J Clin Pediatr Dent 2016;9(4):313-319.

Xylitol-containing products for preventing dental caries in children and adults

BACKGROUND

Dental caries is a highly prevalent chronic disease which affects the majority of people. It has been postulated that the consumption of xylitol could help to prevent caries. The evidence on the effects of xylitol products is not clear and therefore it is important to summarise the available evidence to determine its effectiveness and safety.

OBJECTIVES

To assess the effects of different xylitol-containing products for the prevention of dental caries in children and adults.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Oral Health Group Trials Register (to 14 August 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2014, Issue 7), MEDLINE via OVID (1946 to 14 August 2014), EMBASE via OVID (1980 to 14 August 2014), CINAHL via EBSCO (1980 to 14 August 2014), Web of Science Conference Proceedings (1990 to 14 August 2014), Proquest Dissertations and Theses (1861 to 14 August 2014). We searched the US National Institutes of Health Trials Register (http://clinicaltrials.gov) and the WHO Clinical Trials Registry Platform for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of xylitol products on dental caries in children and adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the results of the electronic searches, extracted data and assessed the risk of bias of the included studies. We attempted to contact study authors for missing data or clarification where feasible. For continuous outcomes, we used means and standard deviations to obtain the mean difference and 95% confidence interval (CI). We used the continuous data to calculate prevented fractions (PF) and 95% CIs to summarise the percentage reduction in caries. For dichotomous outcomes, we reported risk ratios (RR) and 95% CIs. As there were less than four studies included in the meta-analysis, we used a fixed-effect model. We planned to use a random-effects model in the event that there were four or more studies in a meta-analysis.

MAIN RESULTS

We included 10 studies that analysed a total of 5903 participants. One study was assessed as being at low risk of bias, two were assessed as being at unclear risk of bias, with the remaining seven being at high risk of bias.The main finding of the review was that, over 2.5 to 3 years of use, a fluoride toothpaste containing 10% xylitol may reduce caries by 13% when compared to a fluoride-only toothpaste (PF -0.13, 95% CI -0.18 to -0.08, 4216 children analysed, low-quality evidence).The remaining evidence on children, from small single studies with risk of bias issues and great uncertainty associated with the effect estimates, was insufficient to determine a benefit from xylitol products. One study reported that xylitol syrup (8 g per day) reduced caries by 58% (95% CI 33% to 83%, 94 infants analysed, low quality evidence) when compared to a low-dose xylitol syrup (2.67 g per day) consumed for 1 year.The following results had 95% CIs that were compatible with both a reduction and an increase in caries associated with xylitol: xylitol lozenges versus no treatment in children (very low quality body of evidence); xylitol sucking tablets versus no treatment in infants (very low quality body of evidence); xylitol tablets versus control (sorbitol) tablets in infants (very low quality body of evidence); xylitol wipes versus control wipes in infants (low quality body of evidence).There was only one study investigating the effects of xylitol lozenges, when compared to control lozenges, in adults (low quality body of evidence). The effect estimate had a 95% CI that was compatible with both a reduction and an increase in caries associated with xylitol.Four studies reported that there were no adverse effects from any of the interventions. Two studies reported similar rates of adverse effects between study arms. The remaining studies either mentioned adverse effects but did not report any usable data, or did not mention them at all. Adverse effects include sores in the mouth, cramps, bloating, constipation, flatulence, and loose stool or diarrhoea.

AUTHORS' CONCLUSIONS

We found some low quality evidence to suggest that fluoride toothpaste containing xylitol may be more effective than fluoride-only toothpaste for preventing caries in the permanent teeth of children, and that there are no associated adverse-effects from such toothpastes. The effect estimate should be interpreted with caution due to high risk of bias and the fact that it results from two studies that were carried out by the same authors in the same population. The remaining evidence we found is of low to very low quality and is insufficient to determine whether any other xylitol-containing products can prevent caries in infants, older children, or adults.

Regulation of Streptococcus mutans PTS Bio by the transcriptional repressor NigR

Streptococcus mutans is implicated in human dental caries, and the carbohydrate metabolism of this organism plays an important role in the formation of this disease. Carbohydrate transport and metabolism are essential for the survival of S. mutans in the oral cavity. It is known that a unique phosphoenolpyruvate-sugar phosphotransferase system PTS(B) (io) of S. mutans UA159 is expressed in sucrose-grown biofilms (Mol Oral Microbiol 28: 2013; 114). In this study we analyzed the transcriptional regulation of the operon (O(B) (io) ) encoding the PTS(B) (io) and showed that it was repressed by NigR, a LacI-like transcriptional regulator. Using electro-mobility shift assay, we described two operators to which NigR bound with different affinities. We also identified the transcriptional start site and showed that one of the operators overlaps with the promoter and presumably represses initiation of transcription. Mutational analyses revealed the key nucleotides in the operators required for high-affinity binding of NigR. PTS(B) (io) is expressed in S. mutans biofilms so understanding its regulation may provide improved strategies for caries treatment and prevention.

Salivary mucin 19 glycoproteins: innate immune functions in Streptococcus mutans-induced caries in mice and evidence for expression in human saliva

Saliva functions in innate immunity of the oral cavity, protecting against demineralization of teeth (i.e. dental caries), a highly prevalent infectious disease associated with Streptococcus mutans, a pathogen also linked to endocarditis and atheromatous plaques. Gel-forming mucins are a major constituent of saliva. Because Muc19 is the dominant salivary gel-forming mucin in mice, we studied Muc19(-/-) mice for changes in innate immune functions of saliva in interactions with S. mutans. When challenged with S. mutans and a cariogenic diet, total smooth and sulcal surface lesions are more than 2- and 1.6-fold higher in Muc19(-/-) mice compared with wild type, whereas the severity of lesions are up to 6- and 10-fold higher, respectively. Furthermore, the oral microbiota of Muc19(-/-) mice display higher levels of indigenous streptococci. Results emphasize the importance of a single salivary constituent in the innate immune functions of saliva. In vitro studies of S. mutans and Muc19 interactions (i.e. adherence, aggregation, and biofilm formation) demonstrate Muc19 poorly aggregates S. mutans. Nonetheless, aggregation is enhanced upon adding Muc19 to saliva from Muc19(-/-) mice, indicating Muc19 assists in bacterial clearance through formation of heterotypic complexes with salivary constituents that bind S. mutans, thus representing a novel innate immune function for salivary gel-forming mucins. In humans, expression of salivary MUC19 is unclear. We find MUC19 transcripts in salivary glands of seven subjects and demonstrate MUC19 glycoproteins in glandular mucous cells and saliva. Similarities and differences between mice and humans in the expression and functions of salivary gel-forming mucins are discussed.

The effect of xylitol on dental caries and oral flora

Dental caries, the most chronic disease affecting mankind, has been in the limelight with regard to its prevention and treatment. Professional clinical management of caries has been very successful in cases of different severities of disease manifestations. However, tertiary management of this disease has been gaining attention, with numerous methods and agents emerging on a daily basis. Higher intake of nutritive sweeteners can result in higher energy intake and lower diet quality and thereby predispose an individual to conditions like obesity, cardiovascular disorders, and type 2 diabetes mellitus. Non-nutritive sweeteners have gained popularity as they are sweeter and are required in substantially lesser quantities. Xylitol, a five-carbon sugar polyol, has been found to be promising in reducing dental caries disease and also reversing the process of early caries. This paper throws light on the role and effects of various forms of xylitol on dental caries and oral hygiene status of an individual.

The redox-sensing regulator Rex modulates central carbon metabolism, stress tolerance response and biofilm formation by Streptococcus mutans

The Rex repressor has been implicated in regulation of central carbon and energy metabolism in gram-positive bacteria. We have previously shown that Streptococcus mutans, the primary causative agent of dental caries, alters its transcriptome upon Rex-deficiency and renders S. mutans to have increased susceptibility to oxidative stress, aberrations in glucan production, and poor biofilm formation. In this study, we showed that rex in S. mutans is co-transcribed as an operon with downstream guaA, encoding a putative glutamine amidotransferase. Electrophoretic mobility shift assays showed that recombinant Rex bound promoters of target genes avidly and specifically, including those down-regulated in response to Rex-deficiency, and that the ability of recombinant Rex to bind to selected promoters was modulated by NADH and NAD(+). Results suggest that Rex in S. mutans can function as an activator in response to intracellular NADH/NAD(+) level, although the exact binding site for activator Rex remains unclear. Consistent with a role in oxidative stress tolerance, hydrogen peroxide challenge assays showed that the Rex-deficient mutant, TW239, and the Rex/GuaA double mutant, JB314, were more susceptible to hydrogen peroxide killing than the wildtype, UA159. Relative to UA159, JB314 displayed major defects in biofilm formation, with a decrease of more than 50-fold in biomass after 48-hours. Collectively, these results further suggest that Rex in S. mutans regulates fermentation pathways, oxidative stress tolerance, and biofilm formation in response to intracellular NADH/NAD(+) level. Current effort is being directed to further investigation of the role of GuaA in S. mutans cellular physiology.

Clinical Efficacy and Effects of Xylitol Wipes on Bacterial Virulence

The aim of the study was to investigate whether xylitol-wipe use in young children prevented caries by affecting bacterial virulence. In a double-blinded randomized controlled clinical trial, 44 mother-child pairs were randomized to xylitol-wipe or placebo-wipe groups. Salivary mutans streptococci levels were enumerated at baseline, 6 months, and one year. Ten mutans streptococci colonies were isolated and genotyped from each saliva sample. Genotype-colonization stability, xylitol sensitivity, and biofilm formation of these isolates were studied. Despite a significant reduction in new caries at one year in the xylitol-wipe group, no significant differences were found between the two groups in levels of mutans streptococci. Children in the xylitol-wipe group had significantly fewer retained genotypes (p = 0.06) and more transient genotypes of mutans streptococci (p = 0.05) than those in the placebo-wipe group. At one year, there was no significant difference in the prevalence of xylitol-resistant genotypes or in biofilm formation ability of mutans streptococci isolates between the two groups. The mechanism of the caries-preventive effect of xylitol-wipe use may be related to the stability of mutans streptococci colonization. Further studies with genomic characterization methods are needed to determine specific gene(s) that account for the caries-preventive effect of xylitol.

Effect of xylitol on cariogenic and beneficial oral streptococci: a randomized, double-blind crossover trial

BACKGROUND/PURPOSE

Although habitual consumption of xylitol reduces cariogenic streptococci levels, its effect on beneficial oral streptococci is less clear. The main aim of the study is to investigate the effect of short-term xylitol consumption on the oral beneficial streptococci level of saliva, Streptococcus sanguinis and S. mitis.

MATERIAL AND METHODS

Twenty four volunteers with a median age of 23.7 years (range: 20-28) harboring Streptococcus mutans, S. sobrinus, S. sanguinis and S. mitis participated in the randomized, double-blind, cross-over study. The experimental chewing gum (1.5 g/pellet) contained 70% xylitol w/w while the control gum contained 63% sorbitol w/w. Saliva samples were collected before and after two three-week test periods with a four-week washout interval. Colony-forming units (CFU)/ml were enumerated for the estimation of S. mutans levels on Mitis Salivarius-Mutans valinomycin (MS-MUTV), S. sobrinus on Mitis Salivarius-Sobrinus (MS-SOB), S. sanguinis on Modified Medium 10-Sucrose (MM10-S) and S. mitis on Mitis Salivarius Agar with Tellurite (MSAT) media.

RESULTS

The S. mutans and S. sobrinus counts of the saliva samples decreased significantly (p = 0.01 and p = 0.011, respectively) in the xylitol gum group but not in the sorbitol gum group. The salivary S. sanguinis and S. mitis counts did not decrease in both xylitol and sorbitol gum groups.

CONCLUSIONS

Based on the findings of this study, xylitol consumption reduced S. mutans and S. sobrinus counts in saliva but appeared not to effect numbers of S. sanguinis and S. mitis in saliva. So, habitual consumption of xylitol reduces cariogenic streptococci levels without any effect on beneficial sterptococci for the oral cavity.

Point-of-care salivary microbial tests for detection of cariogenic species--clinical relevance thereof--review

Dental caries is a highly prevalent multifactorial disease that can result in serious health impairment. It was shown that oral bacteria play a significant role in caries development. Point-of-care (POC) salivary microbial tests for detection of cariogenic species have been investigated as a potential tool for caries risk assessment. This review aims to evaluate clinical relevance of these tests in the light of recent scientific evidence. Methodology involved PubMed search using key words salivary microbial tests, cariogenic bacteria and caries risk prediction. Articles obtained by the search were cross-referenced to obtain further sources. Specificity and negative-predictive value of these tests are higher than their sensitivity and positive value. Predictive power of the POC salivary microbial tests as a single predictor is generally weak, although it increases when included in multifactorial models for caries prediction. Literature findings support the use of these tests for screening of at-risk individuals in a population of young preschool children without visible caries and for motivation of subjects on individual level. POC salivary microbial tests are simple and inexpensive and, therefore, may be advantageous from public health perspective.

Sugar alcohol sweeteners as alternatives to sugar with special consideration of xylitol

INTRODUCTION

Dental caries is a diet-associated disease which continues to be a serious health problem in most industrialized and developing countries. Strategies to maximize caries prevention should automatically consider the use of sugar substitutes. It is important that public health authorities are made cognizant of the availability of new polyol-type sugar substitutes.

REVIEW SUMMARY

Clinical studies have shown that xylitol, a natural, physiologic sugar alcohol of the pentitol type, can be used as a safe and effective caries-limiting sweetener. Habitual use of xylitol-containing food and oral hygiene adjuvants has been shown to reduce the growth of dental plaque, to interfere with the growth of caries-associated bacteria, to decrease the incidence of dental caries, and to be associated with remineralization of caries lesions. Numerous public regulatory bodies have endorsed the use of xylitol as a caries-limiting agent. Other sugar alcohols that have been successfully used as sugar substitutes include D-glucitol (sorbitol), which, however, owing to its hexitol nature, normally has no strong effect on the mass and adhesiveness of bacterial plaque and on the growth of mutans streptococci. A tetritol-type alditol, erythritol, has shown potential as a non-cariogenic sugar substitute. Combinations of xylitol and erythritol may reduce the incidence of caries more effectively than either alditol alone.

CONCLUSIONS

Partial sugar substitution with polyols is an important dietary tool in the prevention of dental caries that should be used to enhance existing fluoride-based caries prevention programmes. The most effective method of conveying this information to the public is through a proper health claim for these alditols in food labelling. The present review summarizes clinical and biochemical aspects of the above three dietary polyols and emphasizes the role of sugar substitution as a potential health-promoting strategy.

Caries Inhibition by and Safety of Lactobacillus paracasei DSMZ16671

Lactobacillus paracasei DSMZ16671, even if heat-killed, sensitively co-aggregates mutans streptococci specifically. Mutans streptococci are strongly implicated in caries induction in humans and rodents. We hypothesized: (1) that S. mutans recoveries from rats’ teeth in vivo will decrease, with an associated decrease in caries, if these lactobacilli are fed to rats in an established caries model; and (2) that toxicological assays of these lactobacilli will show them to be benign. Four groups of specific-pathogen-free rats were formed: S. mutans 10449S-inoculated/16671-supplemented diet; un-inoculated/16671-supplemented diet; S. mutans 10449S-inoculated/placebo diet; and un-inoculated/placebo diet. Standard tests of toxicity and mutagenicity of heat-killed DSMZ16671 were performed. S. mutans recoveries were significantly reduced both in mid-experiment and at termination, as were caries lesion scores for the rats inoculated by S. mutans and fed the DSMZ16671 supplement, by comparison with controls. Neither toxicity nor mutagenicity of DSMZ16671 was detected. Use of heat-killed DSMZ16671 is efficacious in rats and appears safe.

An examination of the advances in science and technology of prevention of tooth decay in young children since the Surgeon General's Report on Oral Health

This paper addresses a number of areas related to how effectively science and technology have met Healthy People 2010 goals for tooth decay prevention. In every area mentioned, it appears that science and technology are falling short of these goals. Earlier assessments identified water fluoridation as one of the greatest public health accomplishments of the last century. Yet, failure to complete needed clinical and translational research has shortchanged the caries prevention agenda at a critical juncture. Science has firmly established the transmissible nature of tooth decay. However, there is evidence that tooth decay in young children is increasing, although progress has been made in other age groups. Studies of risk assessment have not been translated into improved practice. Antiseptics, chlorhexidine varnish, and polyvinylpyrrolidone iodine (PVI-I) may have value, but definitive trials are needed. Fluorides remain the most effective agents, but are not widely disseminated to the most needy. Fluoride varnish provides a relatively effective topical preventive for very young children, yet definitive trials have not been conducted. Silver diamine fluoride also has potential but requires study in the United States. Data support effectiveness and safety of xylitol, but adoption is not widespread. Dental sealants remain a mainstay of public policy, yet after decades of research, widespread use has not occurred. We conclude that research has established the public health burden of tooth decay, but insufficient research addresses the problems identified in the report Oral Health in America: A Report of the Surgeon General. Transfer of technology from studies to implementation is needed to prevent tooth decay among children. This should involve translational research and implementation of scientific and technological advances into practice.

Molecular characterization of group A Streptococcus maltodextrin catabolism and its role in pharyngitis

We previously demonstrated that the cell-surface lipoprotein MalE contributes to GAS maltose/maltodextrin utilization, but MalE inactivation does not completely abrogate GAS catabolism of maltose or maltotriose. Using a genome-wide approach, we identified the GAS phosphotransferase system (PTS) responsible for non-MalE maltose/maltotriose transport. This PTS is encoded by an open reading frame (M5005_spy1692) previously annotated as ptsG based on homology with the glucose PTS in Bacillus subtilis. Genetic inactivation of M5005_spy1692 significantly reduced transport rates of radiolabelled maltose and maltotriose, but not glucose, leading us to propose its reannotation as malT for maltose transporter. The DeltamalT, DeltamalE and DeltamalE:malT strains were significantly attenuated in their growth in human saliva and in their ability to catabolize alpha-glucans digested by purified human salivary alpha-amylase. Compared with wild-type, the three isogenic mutant strains were significantly impaired in their ability to colonize the mouse oropharynx. Finally, we discovered that the transcript levels of maltodextrin utilization genes are regulated by competitive binding of the maltose repressor MalR and catabolite control protein A. These data provide novel insights into regulation of the GAS maltodextrin genes and their role in GAS host-pathogen interaction, thereby increasing the understanding of links between nutrient acquisition and virulence in common human pathogens.

A surrogate method for comparison analysis of salivary concentrations of Xylitol-containing products

Background

Xylitol chewing gum has been shown to reduce Streptococcus mutans levels and decay. Two studies examined the presence and time course of salivary xylitol concentrations delivered via xylitol-containing pellet gum and compared them to other xylitol-containing products.

Methods

A within-subjects design was used for both studies. Study 1, adults (N = 15) received three xylitol-containing products (pellet gum (2.6 g), gummy bears (2.6 g), and commercially available stick gum (Koolerz, 3.0 g)); Study 2, a second group of adults (N = 15) received three xylitol-containing products (pellet gum, gummy bears, and a 33% xylitol syrup (2.67 g). For both studies subjects consumed one xylitol product per visit with a 7-day washout between each product. A standardized protocol was followed for each product visit. Product order was randomly determined at the initial visit. Saliva samples (0.5 mL to 1.0 mL) were collected at baseline and up to 10 time points (~16 min in length) after product consumption initiated. Concentration of xylitol in saliva samples was analyzed using high-performance liquid chromatography. Area under the curve (AUC) for determining the average xylitol concentration in saliva over the total sampling period was calculated for each product.

Results

In both studies all three xylitol products (Study 1: pellet gum, gummy bears, and stick gum; Study 2: pellet gum, gummy bears, and syrup) had similar time curves with two xylitol concentration peaks during the sampling period. Study 1 had its highest mean peaks at the 4 min sampling point while Study 2 had its highest mean peaks between 13 to 16 minutes. Salivary xylitol levels returned to baseline at about 18 minutes for all forms tested. Additionally, for both studies the total AUC for the xylitol products were similar compared to the pellet gum (Study 1: pellet gum – 51.3 μg.min/mL, gummy bears – 59.6 μg.min/mL, and stick gum – 46.4 μg.min/mL; Study 2: pellet gum – 63.0 μg.min/mL, gummy bears – 55.9 μg.min/mL, and syrup – 59.0 μg.min/mL).

Conclusion

The comparison method demonstrated high reliability and validity. In both studies other xylitol-containing products had time curves and mean xylitol concentration peaks similar to xylitol pellet gum suggesting this test may be a surrogate for longer studies comparing various products.

Sucrose metabolism contributes to in vivo fitness of Streptococcus pneumoniae

We characterized two sucrose-metabolizing systems -sus and scr- and describe their roles in the physiology and virulence of Streptococcus pneumoniae in murine models of carriage and pneumonia. The sus and scr systems are regulated by LacI family repressors SusR and ScrR respectively. SusR regulates an adjacent ABC transporter (susT1/susT2/susX) and sucrose-6-phosphate (S-6-P) hydrolase (susH). ScrR controls an adjacent PTS transporter (scrT), fructokinase (scrK) and second S-6-P hydrolase (scrH). sus and scr play niche-specific roles in virulence. The susH and sus locus mutants are attenuated in the lung, but dispensable in nasopharyngeal carriage. Conversely, the scrH and scr locus mutants, while dispensable in the lung, are attenuated for nasopharyngeal colonization. The scrH/susH double mutant is more attenuated than scrH in the nasopharynx, indicating SusH can substitute in this niche. Both systems are sucrose-inducible, with ScrH being the major in vitro hydrolase. The scrH/susH mutant does not grow on sucrose indicating that sus and scr are the only sucrose-metabolizing systems in S. pneumoniae. We propose a model describing hierarchical regulation of the scr and sus systems by the putative inducer, S-6-P. The transport and metabolism of sucrose or a related disaccharide thus contributes to S. pneumoniae colonization and disease.

Streptococcus gordonii's sequenced strain CH1 glucosyltransferase determines persistent but not initial colonization of teeth of rats

OBJECTIVE

Extracellular glucan synthesis from sucrose by Streptococcus gordonii, a major dental plaque biofilm bacterium, is assumed important for colonization of teeth; but this hypothesis is un-tested in vivo.

METHODS

To do so, we studied an isogenic glucosyltransferase (Gtf)-negative mutant (strain AMS12, gtfG(-)) of S. gordonii sequenced wild type (WT, strain Challis CH1, gtfG(+)), comparing their in vitro abilities to grow in the presence of glucose and sucrose and, in vivo, to colonize and persist on teeth and induce caries in rats. Weanling rats of two breeding colonies, TAN:SPFOM(OM)BR and TAN:SPFOM(OMASF)BR, eating high sucrose diet, were inoculated with either the WT (gtfG(+)), its isogenic gtfG(-) mutant, or reference strains of Streptococcus mutans. Control animals were not inoculated.

RESULTS

In vitro, the gtfG(-) strain grew at least as rapidly in the presence of sucrose as its WT gtfG(+) progenitor, but formed soft colonies on sucrose agar, consistent with its lack of insoluble glucan synthesis. It also had a higher growth yield due apparently to its inability to channel carbon flow into extracellular glucan. In vivo, the gtfG(-) mutant initially colonized as did the WT but, unlike the WT, failed to persist on the teeth as shown over time. By comparison to three S. mutans strains, S. gordonii WT, despite its comparable ecological success on the teeth, was associated with only modest caries induction. Failure of the gtfG(-) mutant to persistently colonize was associated with slight diminution of caries scores by comparison with its gtfG(+) WT.

CONCLUSIONS

Initial S. gordonii colonization does not depend on Gtf-G synthesis; rather, Gtf-G production determines S. gordonii's ability to persist on the teeth of sucrose-fed rats. S. gordonii appears weakly cariogenic by comparison with S. mutans reference strains.

Comparative genome hybridization of Streptococcus mutans strains

The basis for genotypic and phenotypic variation within Streptococcus mutans is poorly understood but the availability of the genome sequence of strain UA159 provides an opportunity for comparative studies. Genomic DNA prepared from nine strains of S. mutans was used to probe a microarray consisting of oligonucleotides representing 1948 open reading frames of S. mutans UA159. A total of 385 (20%) of the UA159 open reading frames were found to be absent from one or more of the test strains. Absent open reading frames frequently occurred in blocks of adjacent open reading frames and represented regions previously experimentally detected by polymerase chain reaction, predicted genomic islands and insertion sequence elements as well as novel open reading frames. Approximately half appear to involve foreign DNA acquired by horizontal transmission. The results indicate the existence of distinct core and dispensable genomes and may help explain the phenotypic and genotypic variation within S. mutans.

Risk Indicators of Pre-Eclampsia in North Jordan: Is Dental Caries Involved?

BACKGROUND

Despite a huge body of published research, understanding the basic pathology that leads to pre-eclampsia is still incomplete. This study was conducted among women in north Jordan to determine factors associated with pre-eclampsia and to determine if dental caries was involved.

METHODS

A case-control study was carried out among women who delivered at Princess Badea Teaching Hospital, Irbid, North Jordan, between September 1, 2004 and January 1, 2005. 115 women with pre-eclampsia and 230 normotensive controls were included in the study. Information regarding participants' demographics, antenatal history and family history were collected through personal interviews. Several oral parameters were measured for each participant.

RESULTS

In multivariate analysis, factors found to be associated with increased odds of pre-eclampsia were age > or =35 years (adjusted OR 2.20; 95% CI 1.08, 4.48), nulliparity (adjusted OR 2.73; 95% CI 1.38, 5.39), emotional stress during pregnancy (adjusted OR 4.22; 95% CI 1.79, 9.90), maternal history of pre-eclampsia (adjusted OR 16.04; 95% CI 5.82, 44.22), family history of cardiovascular diseases (adjusted OR 2.82; 95% CI 1.22, 6.51), family history of pre-eclampsia (adjusted OR 23.26; 95% CI 5.07, 106.78), twin births (adjusted OR 37.79; 95% CI 4.22, 338.51), and Body Mass Index (BMI). In comparison with women with pre-pregnancy BMI <25, adjusted OR were 1.97, 95% CI 1.02, 3.81 for women with BMI from 25 to 29.9, and 3.31, 95% CI 1.36, 8.03 for women with BMI > or =30. Mean decayed teeth surface was found to be associated with increased odds of pre-eclampsia (adjusted OR 1.14, 95% CI 1.03, 1.27).

CONCLUSION

This study demonstrated no difference to reported risk indicators of pre-eclampsia in other populations, but adds that dental caries may have an association with increased odds of pre-eclampsia.