Selection for Streptococcus mutans with an altered xylitol transport capacity in chronic xylitol consumers

Effect of Xylitol on Inhibition and Eradication of Pseudomonas aeruginosa PAO1 and Methicillin-Resistant Staphylococcus aureus Biofilms in an Alginate Bead Model

Biofilms formed by Pseudomonas aeruginosa and Staphylococcus aureus, along with their antibiotic tolerance have posed challenges to treatment strategies for lung, wound, and other infections, particularly when co-infecting. In the present study, the inhibitory effect of xylitol on biofilm formation, as well as its eradication potential on pre-established biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model were tested. Xylitol concentrations of 2, 1, and 0.5 M reduced biofilm formation by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm in a concentration-dependent manner. Additionally, biofilms formed by these species were subjected to treatment with xylitol. Xylitol was also capable of eradicating biofilms established by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm by at least 20%, with the most effective eradication observed for P. aeruginosa strain PAO1. The present study indicates the effectiveness of xylitol as both an inhibitory and eradicating agent against biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model, which mimics the in vivo characteristics of P. aeruginosa aggregates.

Methods of Primary Clinical Prevention of Dental Caries in the Adult Patient: An Integrative Review

AIM

Preventive approaches to oral health diseases, mainly dental caries, require individual and collective policies. Thus, this review was conducted to identify the primary prevention methods of dental caries in adults to improve oral health at the clinical and community levels.

METHODS

This review followed the PICO strategy with the research question: "What are the methods of primary prevention of dental caries, in adults, for improving and maintaining oral health integrating clinical and community-based strategies?" Electronic screening was carried out by two independent reviewers in five databases (MedLine/PubMed, SciELO, Web of Science, Cochrane Library, and LILACS) to find relevant publications between 2015-2022. We applied eligibility criteria for selection of the articles. The following MeSH terms were used: "Primary Prevention"; "Adult"; "Oral Health"; "Dental Caries"; "Fluorides, Topical"; "Fluoride Varnishes"; "Pit and Fissure Sealants"; "Preventive Dentistry". Although the term "Prevention strategy" is not a MeSH descriptor, several correlated terms appeared and were used in the search engines: "Preventative Care", "Disease Prevention, Primary", and "Prevention, Primary". The tool provided by the JBI organization (Joanna Briggs Institute) was used to assess the quality of the included studies.

RESULTS

Nine studies were included. Overall, it was found that the main primary prevention methods applied in dentistry in adults are the application of pit and fissure sealants, topical application of fluoride performed in the dental clinic, use of fluoridated toothpaste, mouthwash with chlorhexidine at home, use of xylitol, the recommendation for regular appointments with the dentist, and the need to inform patients about the saliva buffer capacity and adoption of a non-cariogenic diet. For that purpose, preventive policies should be taken to prevent dental caries. These include three major challenges: providing the adult population with more knowledge regarding their oral health, empowering patients through adopting healthy lifestyles, and developing new preventive strategies and awareness campaigns aimed at the adult population to promote proper oral health habits.

CONCLUSIONS

A small number of studies were found whose participants were adult patients. There was some consistency regarding primary prevention methods in our studies. However, good quality randomized control studies are still required to define the best intervention strategies for adult caries prevention.

Xylitol Inhibits Growth and Blocks Virulence in Serratia marcescens

Serratia marcescens is an opportunistic nosocomial pathogen and causes wound and burn infections. It shows high resistance to antibiotics and its pathogenicity is mediated by an arsenal of virulence factors. Another therapeutic option to such infections is targeting quorum sensing (QS), which controls the expression of different S. marcescens virulence factors. Prevention of QS can deprive S. marcescens from its bacterial virulence without applying stress on the bacterial growth and facilitates the eradication of the bacteria by immunity. The objective of the current study is to explore the antimicrobial and antivirulence activities of xylitol against S. marcescens. Xylitol could inhibit the growth of S. marcescens. Sub-inhibitory concentrations of xylitol could inhibit biofilm formation, reduce prodigiosin production, and completely block protease activity. Moreover, xylitol decreased swimming motility, swarming motility and increased the sensitivity to hydrogen peroxide. The expression of rsmA, pigP, flhC, flhD fimA, fimC, shlA bsmB, and rssB genes that regulate virulence factor production was significantly downregulated by xylitol. In silico study showed that xylitol could bind with the SmaR receptor by hydrophobic interaction and hydrogen bonding, and interfere with the binding of the natural ligand with SmaR receptor. An in vivo mice survival test confirmed the ability of xylitol to protect mice against the virulence of S. marcescens. In conclusion, xylitol is a growth and virulence inhibitor in S. marcescens and can be employed for the treatment of S. marcescens wound and burn infections.

Anticariogenic potential of white cheese, xylitol chewing gum, and black tea

Objective

This study aimed to examine the effects of these foods on plaque pH and the potential development of tooth decay.

Materials and Methods

Plaque pH was measured using the sampling method before and after 1, 5, 10, 20, 30, 45, and 60 min following consumption of these foods individually and after rinsing with a 10% sucrose solution. Statistical analysis was performed using one-way ANOVA and Tukey honestly significant difference post hoc tests (α = 0.05).

Results

Although there were statistically significant differences in all test groups except the BT (P = 0.620) and sucrose + XCG (P = 0.550) groups in time, none of the participants chosen for this study were having a plaque pH value anywhere close to the critical value (pH = 5.5).

Conclusion

WC, BT, and XCG are advisable as anticariogenic foods because pH values are not below critical value.

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 in preventing dental caries: A systematic review and meta-analyses

Xylitol is a sugar alcohol having the properties that reduce levels of mutans streptococci (MS) in the plaque and saliva. To assess the role of xylitol in preventing dental caries. Systematic review and meta-analysis developed by Cochrane cooperation were adapted. Electronic search was carried out in PubMed through the period up to 2014. Included clinical studies were done on (1) humans (2) participants include both individuals and as pairs (mother-child) (3) participants using orthodontic appliances (4) xylitol dispensed in any form (5) compare the effect of xylitol on dental caries and on other phenotype that determines the preventive effect on dental caries, such as decayed, missing, and filled (DMF/dmf) and salivary or plaque MS level. Twenty articles of the 477 articles initially identified. Among 20 studies indexed, 16 articles were accessed, systematically reviewed, and the meta-analysis was carried out. The evaluation of quality of the studies was done using risk of bias assessment tool. The quality of the studies was high risk and unclear risk for six and five trials. The meta-analysis shows a reduction in DMF/dmf with the standard mean (SM) of -1.09 (95% confidence interval [95% CI], -1.34, -0.83) comparing xylitol to all controls. The effect of DMF/dmf reduction by xylitol to fluoride varnish was with the SM of -1.87 (95% CI, -2.89, -0.84). The subgroup analysis, there was a reduction in MS count with SM of 0.30 (95% CI, 0.05, 0.56) when compared with all other caries preventive strategies; however, it was insignificant. Xylitol was found to be an effective strategy as self-applied caries preventive agent.

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.

Synergistic effect of xylitol and ursolic acid combination on oral biofilms

Objectives

This study was designed to evaluate the synergistic antibacterial effect of xylitol and ursolic acid (UA) against oral biofilms in vitro.

Materials and Methods

S. mutans UA 159 (wild type), S. mutans KCOM 1207, KCOM 1128 and S. sobrinus ATCC 33478 were used. The susceptibility of S. mutans to UA and xylitol was evaluated using a broth microdilution method. Based on the results, combined susceptibility was evaluated using optimal inhibitory combinations (OIC), optimal bactericidal combinations (OBC), and fractional inhibitory concentrations (FIC). The anti-biofilm activity of xylitol and UA on Streptococcus spp. was evaluated by growing cells in 24-well polystyrene microtiter plates for the biofilm assay. Significant mean differences among experimental groups were determined by Fisher's Least Significant Difference (p < 0.05).

Results

The synergistic interactions between xylitol and UA were observed against all tested strains, showing the FICs < 1. The combined treatment of xylitol and UA inhibited the biofilm formation significantly and also prevented pH decline to critical value of 5.5 effectively. The biofilm disassembly was substantially influenced by different age of biofilm when exposed to the combined treatment of xylitol and UA. Comparing to the single strain, relatively higher concentration of xylitol and UA was needed for inhibiting and disassembling biofilm formed by a mixed culture of S. mutans 159 and S. sobrinus 33478.

Conclusions

This study demonstrated that xylitol and UA, synergistic inhibitors, can be a potential agent for enhancing the antimicrobial and anti-biofilm efficacy against S. mutans and S. sobrinus in the oral environment.

Mutans streptococci genetic strains in children with severe early childhood caries: follow-up study at one-year post-dental rehabilitation therapy

Background

Genotypic strains of cariogenic mutans streptococci (MS) may vary in important virulence properties. In previous published studies, we identified 39 MS strains from pediatric patients undergoing full-mouth dental rehabilitation, including the removal and/or repair of carious lesions and application of antimicrobial rinse and fluoride varnish.

Objectives

The objectives of this current 1-year follow-up study are to assess the variability of MS strains that occur at 1-year post-rehabilitation and characterize the xylitol-resistance properties of MS strains that predominate.

Methods

Plaque from five children with severe early childhood caries was collected 1-year post-rehabilitation. MS isolates were subjected to arbitrarily primed-polymerase chain reaction (AP-PCR) for identification of genetic strains and in vitro xylitol-inhibition experiments. To more precisely define strain distributions within each patient, we isolated large numbers of isolates per patient.

Results

MS strains diminished from several strains pre-rehabilitation, to one dominant strain at 1-year post-rehabilitation, with several new emergent strains. The majority of the clinical MS strains, as well as the Streptococcus mutans laboratory strains ATCC 25175 and 35668, were predicted to undergo 50% inhibition with 2.48–5.58% xylitol, with some clinical MS strains being significantly more resistant in vitro.

Conclusions

Our follow-up study using patients from the original cohort demonstrates that specific MS strains are dominant at 1-year post-dental rehabilitation. Most of the clinical MS strains are similar in xylitol resistance to the attenuated S. mutans ATCC control strains, with some strains being more resistant to xylitol in vitro.

Chemical characterization of dissolvable tobacco products promoted to reduce harm

In 2009, the R. J. Reynolds Tobacco Co. released a line of dissolvable tobacco products that are marketed as an alternative to smoking in places where smoking is prohibited. These products are currently available in Indianapolis, IN, Columbus, OH, and Portland, OR. This paper describes the chemical characterization of four such products by gas chromatography-mass spectrometry (GC-MS). The dissolvable tobacco products were extracted and prepared by ultrasonic extraction using acetone, trimethylsilyl derivatization, and headspace solid phase microextraction (SPME). The following compounds were identified in the dissolvables using either ultrasonic extractions or trimethylsilyl derivatization: nicotine, ethyl citrate, palmitic acid, stearic acid, sorbitol, glycerol, and xylitol. The following compounds were identified in the dissolvables using headspace SPME: nicotine, ethyl citrate, cinnamaldehyde, coumarin, vanillin, and carvone. With the exception of nicotine, the compounds identified thus far in the dissolvables are either flavoring compounds or binders. The concentration of free nicotine in the dissolvables was determined from the Henderson-Hasselbalch equation and by measuring the pH and nicotine concentration by GC-MS. The results presented here are the first to reveal the complexity of dissolvable tobacco products and may be used to assess potential oral health effects.

Anti-biofilm strategies and the need for innovations in wound care

With an aging and obese population, chronic wounds such as diabetic ulcers, pressure ulcers, and venous leg ulcers are of an increasingly relevant medical concern in the developed world. Identification of bacterial biofilm contamination as a major contributor to non-healing wounds demands biofilm-targeted strategies to treat chronic wounds. While the current standard of care has proven marginally effective, there are components of standard care that should remain part of the wound treatment regime including systemic and topical antibiotics, antiseptics, and physical debridement of biofilm and devitalized tissue. Emerging anti-biofilm strategies include novel, non-invasive means of physical debridement, chemical agent strategies, and biological agent strategies. While aging and obesity will continue to be major burdens to wound care, the emergence of wounds associated with war require investigation and biotechnology development to address biofilm strategies that manage multi-drug resistant bacteria contaminating the chronic wound. The article presents some of the recent patents related to anti-biofilm strategy in wound care.

In vitro susceptibility of established biofilms composed of a clinical wound isolate of Pseudomonas aeruginosa treated with lactoferrin and xylitol

The medical impact of bacterial biofilms has increased with the recognition of biofilms as a major contributor to chronic wounds such as diabetic foot ulcers, venous leg ulcers and pressure ulcers. Traditional methods of treatment have proven ineffective, therefore this article presents in vitro evidence to support the use of novel antimicrobials in the treatment of Pseudomonas aeruginosa biofilm. An in vitro biofilm model with a clinical isolate of P. aeruginosa was subjected to treatment with either lactoferrin or xylitol alone or in combination. Combined lactoferrin and xylitol treatment disrupted the structure of the P. aeruginosa biofilm and resulted in a >2log reduction in viability. In situ analysis indicated that while xylitol treatment appeared to disrupt the biofilm structure, lactoferrin treatment resulted in a greater than two-fold increase in the number of permeabilised bacterial cells. The findings presented here indicated that combined treatment with lactoferrin and xylitol significantly decreases the viability of established P. aeruginosa biofilms in vitro and that the antimicrobial mechanism of this treatment includes both biofilm structural disruption and permeablisation of bacterial membranes.

Failure of xylitol given three times a day for preventing acute otitis media

BACKGROUND

Xylitol administered regularly 5 times a day after each meal is successful in preventing acute otitis media (AOM) in children, but if given only during respiratory infections it is ineffective against AOM. To find a more convenient dosing regimen, we tested whether xylitol administered 3 times a day reduces the occurrence of AOM.

METHODS

In this 3-month randomized, double-blind trial, 663 healthy day care children were randomized to receive either a control product (n = 331) or xylitol (n = 332). Xylitol was given in chewing gum or in a mixture 3 times a day, the daily dose being 0.5 g in the control group and 9.6 g in the xylitol group. The occurrence of the first AOM diagnosed during any period of respiratory symptoms during the follow-up was the main outcome measure.

RESULTS

At least one AOM episode was diagnosed in 98 of the 331 children who received control products (30%) and in 94 of the 332 who received xylitol products (28%). A total of 142 episodes of AOM were diagnosed in the control group compared with 156 in the xylitol group. The differences were not statistically significant.

CONCLUSIONS

Xylitol given regularly 3 times a day for 3 months during the respiratory infection season failed to prevent AOM.

Dental plaque formation and salivary mutans streptococci in schoolchildren after use of xylitol-containing chewing gum

OBJECTIVE

The aim of this study was to investigate the effect of a fixed daily dose of xylitol on mutans streptococci in saliva and the amount of visible dental plaque. A second aim was to explore if the possible effects differed between children with and without caries experience.

METHODS

The study was designed as a double-blind randomized controlled trial with two parallel arms. All pupils (n=149) in grades 1-6 in a comprehensive school in northern Sweden were invited, and 128 children (mean age=12.7 years) consented to participate. The children were stratified as having caries experience (DMFS/dmfs>or=1) or not before the random allocation to a test or control group. The control group (A) was given two pellets containing sorbitol and maltitol three times daily for 4 weeks, and the test group (B) received corresponding pellets with xylitol as single sweetener (total dose=6.18 g day). Clinical scoring and saliva samples were collected at baseline and immediately after the test period. The outcome measures were visible plaque index, salivary mutans streptococci counts and salivary lactic acid production.

RESULTS

The amount of visible plaque was significantly reduced in both groups after 4 weeks (P<0.05). Likewise, the sucrose-induced lactic acid formation in saliva diminished in both groups (P<0.05). The proportion of mutans streptococci decreased significantly in the test group compared to baseline, but not in the control group (P<0.05). The alterations in the test group seemed most prominent among children without previous caries experience.

CONCLUSIONS

The results suggest that chewing gum with xylitol or sorbitol/maltitol can reduce the amount of dental plaque and acid production in saliva in schoolchildren, but only the xylitol-containing gum may also interfere with the microbial composition.

Streptococcus mutans: fructose transport, xylitol resistance, and virulence

Streptococcus mutans, the primary etiological agent of human dental caries, possesses at least two fructose phosphotransferase systems (PTSs), encoded by fruI and fruCD. fruI is also responsible for xylitol transport. We hypothesized that fructose and xylitol transport systems do not affect virulence. Thus, colonization and cariogenicity of fruI(-) and fruCD(-) single and double mutants, their WT (UA159), and xylitol resistance (X(r)) of S. mutans were studied in rats fed a high-sucrose diet. A sucrose phosphorylase (gtfA(-)) mutant and a reference strain (NCTC-10449S) were additional controls. Recoveries of fruI mutant from the teeth were decreased, unlike those for the other strains. The fruCD mutation was associated with a slight loss of cariogenicity on enamel, whereas mutation of fruI was associated with a loss of cariogenicity in dentin. These results also suggest why xylitol inhibition of caries is paradoxically associated with spontaneous emergence of so-called X(r) S. mutans in habitual human xylitol users.

Difference in the xylitol sensitivity of acid production among Streptococcus mutans strains and the biochemical mechanism

Xylitol inhibits the glycolysis and growth of Streptococcus mutans, but to different degrees among strains. Thus, we studied the biochemical mechanism through which the inhibition varies, using S. mutans strains ATCC 31989, NCTN 10449, and NCIB 11723, which are highly sensitive, moderately sensitive, and resistant to xylitol, respectively, under strictly anaerobic conditions such as those found in deep layers of dental plaque. Xylitol (30 mM) decreased the rate of acid production from glucose (10 mM) in ATCC 31989, NCTC 10449, and NCIB 11723 by 86, 26, and 0%, respectively. The activities of the xylitol : phosphoenolpyruvate phosphotransferase system (PEP-PTS) relative to those of glucose : PEP-PTS were 120, 16, and 3%, respectively. In ATCC 31989 and NCTC 10449, intracellular accumulation of xylitol 5-phosphate and decreases of fructose 1,6-bisphosphate and glucose 6-phosphate were observed. Furthermore, in the presence of xylitol (30 mM), glucose : PEP-PTS activities decreased by 34, 17, and 0%, respectively. These findings indicated that the higher the xylitol : PEP-PTS activity was and the more effectively xylitol decreased glucose : PEP-PTS activity, the more sensitive the strain was to xylitol. These results suggest that the following inhibitory mechanisms are active in the xylitol-sensitive mutans streptococci: direct inhibition of glycolytic enzymes by xylitol 5-phosphate derived from xylitol : PEP-PTS and, possibly, indirect inhibition through competition for the phosphoryl donor, HPr-P, between glucose and xylitol : PEP-PTSs.

Field Trial on Caries Prevention with Xylitol Candies among Disabled School Students

BACKGROUND

In a 1999 survey high caries levels were found among physically disabled school students in Kuwait.

OBJECTIVES

A field study was planned to test the efficacy of xylitol candies in preventing caries among individuals in two special schools in Kuwait.

METHODS

Altogether 176 students were examined in 2002 and 145 (105 in xylitol group and 40 in the control group) after 18 months' intervention. The WHO criteria were used in recording caries according to surfaces (third molars were excluded) by 2 calibrated examiners (E.H., M.S.). The students were allocated to the xylitol group only if the parent/caregiver returned the informed consent form. School health nurses distributed xylitol candies to the students 3 times during the school day (after breakfast and lunch, and before leaving the school).

RESULTS

In the xylitol group, the baseline DS and DMFS scores were 3.4 and 8.2 and in the follow-up 1.9 and 7.1, respectively. In the control group, the baseline scores were DS 3.9 and DMFS 9.8, and the follow-up scores DS 3.9 and DMFS 13.2.

CONCLUSION

Xylitol seemed to have a strong preventive and a clear remineralizing effect on caries.

The next step in infectious disease: taming bacteria

Except for immunization programs our warfare with bacteria has always been a frontal assault with antibiotics. In this warfare we win battles, but with every new battle the enemy gets stronger. We need other options. Recent experience suggests two alternatives. First, public health measures designed to control the spread of infectious disease are associated with the selection of less virulent strains of microorganisms. Second, the same selection pressures obtained by public health measures outside the body are brought into play when we inhibit the adherence of bacteria within the body. Two recent studies using food sugars known to inhibit bacterial adherence show long-term benefits best explained by the previously observed decreases in bacterial virulence, following chronic exposure to the respective substances. Cranberry juice selects for less uropathogenic strains of Escherichia coli and xylitol for less caries producing Streptococcus mutans. The ability of these substances to reduce bacterial adherence in the human host has been known for some time, but poorly utilized. Their in vitro ability to decrease virulence has been reported but not clinically studied.

Cariogenic traits in xylitol-resistant and xylitol-sensitive mutans streptococci

Long-term xylitol consumption leads to the emergence of xylitol-resistant (X-R) mutans streptococci. The aim of the present study was to compare cariogenic traits in X-R and xylitol-sensitive (X-S) strains. Six strains of mutans streptococci, three X-R and three X-S strains, were studied. Xylitol resistance and sensitivity were confirmed by growth in xylitol-supplemented media. Acid production from glucose or fructose or uptake of xylitol was initiated by adding (14)C-labelled glucose, fructose or xylitol to bacterial suspensions. The resultant metabolites were identified by HPLC. Lactate was the major metabolite from glucose, whether the bacteria were grown in the presence or the absence of xylitol. Lactate production per colony-forming unit was lower in X-S cells than in X-R cells. Fructose was metabolized by both X-R and X-S cells. Both X-R and X-S cells took up xylitol, but xylitol-5-P was detected in X-S cells only. Total polysaccharides were measured through production of C(14)-labelled ethanol-insoluble polymers from [U(14)-C]-sucrose. No difference in polysaccharide production was found between X-R and X-S cells. The present study thus does not support the contention that X-R are less cariogenic than X-S mutans streptococci.

How xylitol-containing products affect cariogenic bacteria

BACKGROUND

The authors examined the effect of xylitol, a naturally occurring sweetener, on levels of Streptococcus mutans and S. sobrinus. They also investigated xylitol's mechanism of action.

METHODS

The authors compared cariogenic bacteria levels before and after exposure to xylitol products in children and adults. In the first study, 187 children received xylitol-containing snacks in school for four weeks. In the second study, two adults received xylitol candy for four weeks. Unstimulated saliva samples were taken from all subjects. Gingival samples also were taken from the adults. The authors plated the samples on selective microbiological media. Individual isolates were plated on media with varying concentrations of xylitol, and were identified using specific DNA probes. Genetic relatedness was determined via pulse-field gel electrophoresis.

RESULTS

The children's salivary S. mutans levels remained stable before and after xylitol exposure. Further analysis of the S. mutans isolates was conducted for seven children. Bacteria from five of these children grew with 10 percent or less xylitol at baseline, while the bacteria from all seven children grew with 15 percent xylitol after exposure to the xylitol-containing snacks, suggesting that the S. mutans increased in tolerance to xylitol during exposure. Six children had isolates with the same genotype at both time points. S. mutans and S. sobrinus levels were reduced in one of the adults as a result of xylitol exposure, and the bacterial isolates became more xylitol tolerant. In the second adult, S. mutans and S. sobrinus levels increased, while the subject maintained the same proportion of susceptible and tolerant strains as that at baseline.

CONCLUSIONS

Overall, consumption of xylitol-containing snacks and candy did not reduce S. mutans levels. However, bacteria from five children and one adult became more xylitol tolerant.

CLINICAL IMPLICATIONS

These results provide a basis on which xylitol-containing products can be recommended and xylitol's mechanism of action can be explained to patients.

Xylitol disturbs protein synthesis, including the expression of HSP-70 and HSP-60, in Streptococcus mutans

Xylitol, a natural sugar alcohol and a caries-preventive carbohydrate sweetener, inhibits xylitol-sensitive wild-type Streptococcus mutans but also selects for its natural xylitol-resistant mutants. The aim of the work was to verify the influence of xylitol on heat shock proteins HSP-60 (GroEL-like) and HSP-70 (DnaK-like) in xylitol-sensitive and xylitol-resistant strains. Cells from fresh isolate S. mutans 123.1 were grown at 37 degrees C and constant pH 7.0. The cell culture was stressed by raising the temperature to 43 degrees C or adding xylitol (4% final). Cell proteins labeled with a cocktail of 14C-amino acids were analyzed by SDS-PAGE and autoradiography whereas HSP-60 and HSP-70 were visualized using Western immunoblotting. In both xylitol-sensitive and xylitol-resistant strains, heat stress was associated with an increase of both HSP-60 (63 kDa) and HSP-70 (71 kDa) and a decrease in the intensity of a number of other protein bands compared with cells maintained at 37 degrees C. Exposure to xylitol but not to other polyols induced a decrease of both these heat shock proteins in the xylitol-sensitive strain but did not modify them in the xylitol-resistant mutant. It also decreased all protein bands above 60 kDa together with a 53 kDa protein and increased the amount of 57-, 50- and 40-kDa proteins in the xylitol-sensitive strain whereas the proteins of the xylitol-resistant strain remained unchanged. The results suggest that xylitol is a strong metabolic inhibitor that disturbs protein synthesis and reduces the expression of HSP-70 and HSP-60 proteins in the wild-type xylitol-sensitive S. mutans but not in the xylitol-resistant natural mutant strain.

Influence of maternal xylitol consumption on acquisition of mutans streptococci by infants

Xylitol is effective as a non-cariogenic sugar substitute. Habitual xylitol consumption appears to select for mutans streptococci (MS) with impaired adhesion properties, i.e., they shed easily to saliva from plaque. One hundred sixty-nine mother-child pairs participated in a two-year study exploring whether the mothers' xylitol consumption could be used to prevent mother-child transmission of mutans streptococci. All mothers showed high salivary levels of mutans streptococci during pregnancy. The mothers in the xylitol group (n = 106) were requested to chew xylitol-sweetened gum (65% w/w) at least 2 or 3 times a day, starting three months after delivery. In the two control groups, the mothers received either chlorhexidine (n = 30) or fluoride (n = 33) varnish treatments at 6, 12, and 18 months after delivery. The children did not chew gum or receive varnish treatments. MS were assessed from the mothers' saliva at half-year intervals and from the children's plaque at the one- and two-year examinations. The MS were cultured on Mitis salivarius agars containing bacitracin. The salivary MS levels of the mothers remained high and not significantly different among the three study groups throughout the study. At two years of age, 9.7% of the children in the xylitol, 28.6% in the chlorhexidine, and 48.5% in the fluoride varnish group showed a detectable level of MS. In conclusion, therefore, habitual xylitol consumption by mothers was associated with a statistically significant reduction of the probability of mother-child transmission of MS assessed at two years of age. The effect was superior to that obtained with either chlorhexidine or fluoride varnish treatments performed as single applications at six-month intervals.

Xylitol in caries prevention: what is the evidence for clinical efficacy?

Xylitol has attracted much attention as an alternative sweetener. Essentially all clinical studies concerning the effect of xylitol on caries development consent to its non-cariogenicity and to the beneficial effect of substituting sucrose with xylitol in chewing gums and sweets. However, claims of anti-caries or therapeutic effects, and superiority of xylitol over other polyols are still to be confirmed by well designed and conducted studies from independent research groups.

Growth of xylitol-resistant versus xylitol-sensitive Streptococcus mutans strains in saliva

Five Streptococcus mutans pairs (serotype c S. mutans 10449 and four clinical isolates of S. mutans: 123.1, LG1, OMFA, T10B) were used to find out if the xylitol-resistant (XR) natural mutants of the corresponding xylitol-sensitive (XS) S. mutans parental strains differ in their growth patterns in saliva. The isogenic X natural mutants of the parental S. mutans strains were selected after sequential cultivations in the presence of xylitol and glucose. The XR/XS strains pairs were grown in individual and pooled glucose-supplemented filter-sterilized salivas (one to five sequential cultivations). The two salivas used represented subjects with good or poor support of the growth of S. mutans in vivo. Protease and peptidase activities were determined from the saliva growth media and cell suspensions. Salivary protein profiles were analyzed using SDS-PAGE and native IEF before and after the cultivations. The growth properties of the XR/XS S. mutans pairs were similar in both individual and pooled salivas. Sequential cultivation of all strains did not show any differences in growth patterns. XS strains were inhibited by the presence of xylitol (2% w/v) in pooled saliva, as shown for other glucose-supplemented media. Protease and peptidase activities of the XR/XS S. mutans pairs were low and of similar magnitude. Also, the general hydrolytic properties of most XR/XS S. mutans pairs appeared similar as judged by the small growth-induced changes in salivary protein profiles. In conclusion, saliva, the source of nutrients for salivary microorganisms in vivo, favored neither the XR nor the XS strains of S. mutans.

Effects of xylitol, xylitol-sorbitol, and placebo chewing gums on the plaque of habitual xylitol consumers

Xylitol reduces plaque but the reduction mechanism is largely unknown. The main aim of the present study was to determine whether the xylitol-induced reduction in the amount of plaque and the number of mutans streptococci could be demonstrated in subjects with (presumably) high levels of xylitol-resistant (XR; not inhibited by xylitol) mutans streptococci acquired following previous xylitol consumptions. 37 healthy dental students participated in the double-blind study. All subjects had been uncontrolled, habitual consumers of xylitol-containing products for at least 1 yr before the study. A 1-month washout period was followed by a 2-week test period during which either xylitol, xylitol-sorbitol or unsweetened chewing gum base was chewed 3-5 x a day. Plaque and saliva samples were collected at baseline and at the 2-week point for determination of the amount of plaque, microbiological variables, and hydrolytic enzymes. Mixtures of xylitol and sorbitol seemed to perform equally well with respect to reduction in the amount of plaque but not the number of mutans streptococci. Thus, polyols were the active ingredients of chewing gums able to modulate the amount of plaque and its microbial composition. Xylitol reduced plaque with a mechanism which appeared not to be associated with the study-induced changes in the proportion (%) of mutans streptococci in plaque, the number of salivary mutans streptococci, the proportion of XR strains in plaque or saliva, or the hydrolytic enzyme activities of plaque.

Are sodium lauryl sulfate-containing toothpastes suitable vehicles for xylitol?

The hypothesis to be tested in this study was that toothpastes containing sodium lauryl sulfate (SLS) is unsuitable vehicles for xylitol. The bacteriostatic (and cariostatic) effect of xylitol is assumed to be caused by intracellular accumulation of xylitol-5-P in plaque bacteria. Experiments were designed to investigate whether presence of SLS would affect the uptake of xylitol by interacting with the bacterial membranes and thus inhibit xylitol-5-P formation. It was shown in an in vitro study that even very low concentrations of the strong anionic detergent SLS inhibited uptake of xylitol and xylitol-5-phosphate formation by dental plaque totally. The mild nonionic detergent ethoxylated stearyl alcohol (30x EO) had no such effect. In vivo experiments with toothpastes containing xylitol and either the strong or the mild detergent, showed that xylitol in toothpaste with SLS was not available for the plaque bacteria and gave no adaptation to xylitol, whereas in the presence of 30x EO it was available, and a xylitol adaptation was observed. Glucose metabolism, which was also studied for the plaque samples, was not significantly affected by presence of any of the 2 detergents, indicating that the amounts of xylitol in toothpastes were presumably too low to give clinical significant effects, even when mild detergents are used.

Emergence of multiple xylitol-resistant (fructose PTS-) mutants from human isolates of mutans streptococci during growth on dietary sugars in the presence of xylitol

The growth inhibition of mutans streptococci is one of the proposed mechanisms of action of xylitol, a caries-preventive natural carbohydrate sweetener. Xylitol is taken up and accumulated as non-metabolizable, toxic xylitol phosphate via a constitutive fructose PTS, and selects, during in vitro growth at the expense of glucose, for natural xylitol-resistant mutants that lack constitutive fructose PTS activity. Since long-term xylitol consumption leads to the emergence of xylitol-resistant mutans populations in humans in an oral environment containing sugars of dietary origin, we wanted to test the hypothesis that xylitol-resistant cells could be selected from mutans streptococci strains during in vitro growth on fructose, sucrose, or lactose. Three laboratory strains and three fresh mutans streptococcal isolates were repeatedly transferred in trypticase-yeast extract medium supplemented with glucose, fructose, sucrose, or lactose in the presence and absence of xylitol. Depending on the growth sugar, the presence of xylitol resulted in the selection of xylitol-resistant populations for several of the six strains tested, but not necessarily in the presence of all four sugars. All six strains rapidly became xylitol-resistant when grown on glucose in the presence of xylitol. All three fresh isolates became xylitol-resistant after 9 to 16 transfers in the presence of fructose or sucrose plus xylitol, while none of the laboratory strains became xylitol-resistant after 16 transfers in the presence of these sugars. The growth rates of 12 xylitol-resistant mutants in the presence of eight sugars suggested the existence of various types of xylitol-resistant mutants. The data partially explain the occurrence of xylitol-resistant mutans populations in long-term xylitol consumers and suggest a mechanism consistent with a selection process. Since various preliminary results suggest that xylitol-resistant natural mutants may be less virulent and less cariogenic than their parent strains, this selection process may alter, for the better, the mutans streptococci population of the plaque and play a role in the caries-preventive action of xylitol.

Effect of xylitol on growth of nasopharyngeal bacteria in vitro

Xylitol is known to reduce caries by inhibiting the growth of Streptococcus mutans. We hypothesized that xylitol could also affect the growth of other nasopharyngeal bacterial flora, which could be important when considering respiratory infections caused by these bacteria. We studied this in vitro by adding xylitol to the medium and observed that 1 and 5% xylitol reduced markedly the growth of alpha-hemolytic streptococci, including S. pneumoniae. It reduced slightly the growth of beta-hemolytic streptococci but not that of Haemophilus influenzae or Moraxella catarrhalis. The inhibitory growth pattern was similar to that previously seen with S. mutans, which may indicate a similarity in the enzymatic processing of five-carbon sugars such as xylitol. This sugar alcohol is a widely used sweetener, and the concentrations used in our experiments are easily achieved in the oral cavity. If xylitol reduces the growth of S. pneumoniae in the nasopharynx, it could also reduce the carriage of this pathogen and thus have clinical significance in the prevention of pneumococcal diseases.

Cariologic aspects of xylitol and its use in chewing gum: a review

Several studies indicate that xylitol is not metabolized to acids either in pure cultures of oral microorganisms in vitro or in dental plaque in vivo. Chronic consumption of xylitol-sweetened chewing gum resulted in reduction of dental plaque, suppression of mutans streptococci, and reduced adhesiveness of plaque. So far, four field studies with regimens including chewing gum and other xylitol-containing products and four clinical trials have been carried out. All of the latter studies showed that a daily intake of two to three pieces of xylitol gum resulted in a defined reduction of caries. There are indications that regular and prolonged use of xylitol chewing gum may have a caries-preventive effect.

Xylitol 5-P formation by dental plaque after 12 weeks' exposure to a xylitol/sorbitol containing chewing gum

Five subjects used xylitol-containing chewing gum for 12 wk. Dental plaque was collected before and after the exposure to xylitol. The plaque samples were examined for their capacity to form xylitol 5-P by incubation with 14C labeled xylitol, extraction and separation on HPLC. It was found that the capacity of the plaque to form xylitol 5-P was not reduced during the xylitol exposure in any of the subjects. No other xylitol-derived metabolites were observed. The inhibitory capacity of xylitol thus appears to be maintained after 12 wk exposure to xylitol.

Effect of xylitol consumption on the plaque-saliva distribution of mutans streptococci and the occurrence and long-term survival of xylitol-resistant strains

Since the exposure of mutans streptococci to xylitol is known to select for xylitol-resistant (XR) natural mutants, the occurrence and long-term survival of such xylitol-resistant strains was evaluated in a cross-sectional sampling of participants of the Ylivieska xylitol study four years after the original two-year experimental period. Paraffin-stimulated whole saliva was first collected, and then plaque was collected and pooled. The salivary and dental plaque mutans streptococci were enumerated after growth on TSY20B agar. The proportion of XR strains was determined by autoradiography with 14C-xylitol. A strong and significant correlation (r = 0.645 and p = 0.005) between the number of mutans streptococci in saliva and in dental plaque was observed in non-consumers of xylitol. Such a correlation totally disappeared (r = 0.098 and p = 0.612) in xylitol-exposed consumers (habitual and former xylitol-consumers). The proportion of the salivary XR mutants (35%) in non-consumers (n = 16) was significantly lower than in the xylitol-exposed consumers (79%) (n = 27), (p = 0.0001) or in former consumers (75%) (n = 13), (p = 0.0008) or in the habitual consumers (83%) (n = 14), (p = 0.004). The proportion of XR mutants in dental plaque was, on the average, much lower than in the corresponding saliva. The proportion of XR in the plaque of xylitol non-consumers was half of that of the xylitol-exposed group, but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular xylitol-phosphate hydrolysis and efflux of xylitol in Streptococcus sobrinus

The parental strain Streptococcus sobrinus (Streptococcus mutans ATCC 27352), which is known to transport, phosphorylate and accumulate xylitol intracellularly as nonmetabolizable xylitol-phosphate (xylitol-sensitive (XS) strain) and its xylitol-resistant (XR) spontaneous mutant were used to further investigate the inhibitory action of xylitol on oral streptococci. Fructose-grown XR cells did not accumulate xylitol-phosphate, indicating that the inducible fructose PTS is incapable of transporting the pentitol. The intracellularly accumulated pentitol-phosphate by the XS cells did not prevent the subsequent uptake and degradation of glucose or fructose, despite a drop in the PEP pool and a 50% inhibition of the glucose but not the fructose catabolism. Intracellular dephosphorylation of the pentitol-phosphate and release of xylitol in the extracellular medium resulted in a rapid decrease of the intracellular level of this nonmetabolizable product. A Mg(++)- or Mn(++)-independent sugar-phosphate hydrolysing activity capable of splitting xylitol-phosphate was demonstrated in both XS and XR strains. Preincubation in the presence of N1-ethylmaleimide (NEM) and xylitol or NEM and fructose resulted in the subsequent inhibition of both xylitol uptake and efflux. The efflux kinetic at various temperatures is compatible with a facilitated diffusion by the phosphotransferase system EIIfru without, however, excluding the existence of an additional exit route, but it excludes a simple diffusion exit process. The results are consistent with the existence of a xylitol futile cycle contributing to the growth inhibition of S. sobrinus by the pentitol without excluding a toxic effect of xylitol-phosphate. Discrepancies in the literature on the action of xylitol on S. mutans could be explained in the light of the evidence presented.

Uptake and expulsion of 14C-xylitol by xylitol-cultured Streptococcus mutans ATCC 25175 in vitro

The effect of successive cultivations in the presence of 6% xylitol on the uptake and expulsion of 14C-xylitol was studied using the cells of Streptococcus mutans 25175. Three sequential cultivations did not alter the growth inhibition percentage (approximately 50%) observed in the presence of 6% xylitol. The 14C-xylitol uptake experiments performed with growing and resting cells showed that both the uptake and the expulsion of xylitol were enhanced by xylitol-culturing. Both xylitol-cultured and resting control cells contained only one major labeled compound which was identified as 14C-xylitol 5-phosphate. The label subsequently was expelled from the cells as 14C-xylitol. These results indicate that S. mutans possesses an intracellular xylitol cycle and this cycle is regulated by adding xylitol to the growth medium.

Preparation and Purification of Xylitol-5-Phosphate from a Cell Extract of Lactobacillus casei Cl-16

A simple procedure which yields pure xylitol-5-phosphate is described. A cell extract of Lactobacillus casei Cl-16 from a 6-liter culture was used to synthesize up to 70 mg of xylitol-5-phosphate overnight from xylitol and phosphoenolpyruvate via a xylitol phosphoenolpyruvate:phosphotransferase system with a 53% yield. Centrifugation, filtration, precipitation as a barium salt, and ion-exchange batch chromatography permitted recovery of nearly 90% of the phosphorylated product synthesized. Thin-layer chromatography and enzymatic analysis indicated a purity level of more than 99%. The method was used to synthesize [U- 14 C]xylitol-5-phosphate, and it is suitable for the synthesis of many other nonmetabolizable sugar phosphates.