Enhancing the virulence of Streptococcus sobrinus in rats

Design and study of anticaries effect of different medicinal plants against S.mutans glucosyltransferase

BACKGROUND

The present study was aimed to evaluate the molecular level anticaries effect of different medicinal plants against Streptococcus mutans (S.mutans) glucosyltransferases (gtf).

METHODS

A total of six natural sources named as Terminalia chebula (T.chebula), Psidium guajava (P.guajava), Azadirachta indica (A.indica) and Pongamia pinnata (P.pinnata); two essential oils, clove (Syzygium aromaticum) and peppermint oil (Mentha piperita) were selected as test samples. Hydroalcoholic plant extracts and essential oils were examined for their inhibitory potential on gtf isolated from S.mutans. Polyherbal mouth wash was prepared and its effect on gtf activity was compared with commercial chlorhexidine mouth wash (5%w/v). Enzyme kinetic study was carried out in order to explore the molecular mechanism of enzyme action.

RESULTS

Out of six natural sources tested, A.indica has shown maximum inhibitory effect of 91.647% on gtf and T.chebula has shown IC50 of 1.091 mg/ml which is significant when compared to standard chlorhexidine. From the final result of kinetic analysis it was found that T.chebula, P.guajava and P.pinnata have show uncompetitive inhibition where as A.indica has shown non-competitive inhibition. Surprisingly, both essential oils have shown allosteric inhibition (sigmoidal response). The polyherbal moutwash has shown significant inhibitory potential on gtf (95.936%) when compared to commercial chlorhexidine mouthwash (p < 0.05).

CONCLUSION

All the tested samples have shown considerable gtf inhibitory action. Moreover polyherbal mouth wash has shown promising noncompetitive inhibitory activity against gtf and it could be the future formulation to combat dental caries.

Bacterial Diversity and Community Structure of Supragingival Plaques in Adults with Dental Health or Caries Revealed by 16S Pyrosequencing

Dental caries has a polymicrobial etiology within the complex oral microbial ecosystem. However, the overall diversity and structure of supragingival plaque microbiota in adult dental health and caries are not well understood. Here, 160 supragingival plaque samples from patients with dental health and different severities of dental caries were collected for bacterial genomic DNA extraction, pyrosequencing by amplification of the 16S rDNA V1–V3 hypervariable regions, and bioinformatic analysis. High-quality sequences (2,261,700) clustered into 10,365 operational taxonomic units (OTUs; 97% identity), representing 453 independent species belonging to 122 genera, 66 families, 34 orders, 21 classes, and 12 phyla. All groups shared 7522 OTUs, indicating the presence of a core plaque microbiome. α diversity analysis showed that the microbial diversity in healthy plaques exceeded that of dental caries, with the diversity decreasing gradually with the severity of caries. The dominant phyla of plaque microbiota included Bacteroidetes, Actinobacteria, Proteobacteria, Firmicutes, Fusobacteria, and TM7. The dominant genera included Capnocytophaga, Prevotella, Actinomyces, Corynebacterium, Neisseria, Streptococcus, Rothia, and Leptotrichia. β diversity analysis showed that the plaque microbial community structure was similar in all groups. Using LEfSe analysis, 25 differentially abundant taxa were identified as potential biomarkers. Key genera (27) that potentially contributed to the differential distributions of plaque microbiota between groups were identified by PLS-DA analysis. Finally, co-occurrence network analysis and function predictions were performed. Treatment strategies directed toward modulating microbial interactions and their functional output should be further developed.

Effect of emodin on the cariogenic properties of Streptococcus mutans and the development of caries in rats

Emodin is an active herbal component traditionally used in East Asian countries for treating a variety of diseases. The present study investigated the effects of emodin on specific virulence factors of Streptococcus mutans (S. mutans) in vitro and on caries development in vivo. The growth and acid production of S. mutans were significantly inhibited by emodin (0.5–2 mg/ml). Emodin also significantly suppressed the synthesis of insoluble glucans by S. mutans. Furthermore, the topical application of emodin reduced the incidence and severity of carious lesions in rats. These results suggest that the natural compound emodin may be a novel pharmacological agent for the prevention and treatment of dental caries.

The effect of eugenol on the cariogenic properties of Streptococcus mutans and dental caries development in rats

Eugenol has been widely used in medicine due to its antibacterial, anti-inflammatory, antioxidant, anticancer and analgesic properties. The present study was designed to investigate the effects of eugenol on the cariogenic properties of Streptococcus mutans and dental caries development in rats. Eugenol demonstrated significant inhibitory effects against acid production by S. mutans. The synthesis of water-insoluble glucans by glucosyltransferases was reduced by eugenol. Eugenol also markedly suppressed the adherence of S. mutans to saliva-coated hydroxyapatite beads. Furthermore, topical application of eugenol reduced the incidence and severity of carious lesions in rats. These results suggest that the natural compound eugenol may be a useful therapeutic agent for dental caries.

Rodent model in caries research

The rodent model of dental caries has made fundamental contributions to the understanding of the etiology, pathogenesis, and prevention of this disease. In conducting animal-based investigations, important details considered essential for successful outcome are occasionally overlooked. Adequate number of animals of appropriate age should always be included to ensure sufficient statistical power to draw valid conclusions. Attention should be paid to litter source as it is clear that litter origin may have a profound effect on the outcome. Inclusion of additive in diet may also affect eating pattern. A range of special techniques are available which can expand the role of animals in exploring the pathogenesis of dental caries. The arrival of genetically altered microorganisms along with availability of knock-out rodents offers exciting challenges to further explore the pathogenesis of this still too common disease.

Prevalence of cariogenic streptococci on incisor brackets detected by polymerase chain reaction

INTRODUCTION

Streptococcus mutans and Streptococcus sobrinus are the main causative organisms for enamel demineralization during orthodontic treatment. In this study, we analyzed the prevalence of cariogenic streptococci adhering to incisor brackets.

METHODS

Four incisor brackets from both the maxilla and the mandible were collected from 80 patients at debonding, immediately after the visible plaque index and the gingival bleeding index were measured from the incisors. The genomic DNA of adhered cariogenic streptococci was extracted and amplified by using polymerase chain reaction, and the prevalence of cariogenic streptococci was determined and compared with oral hygiene indexes in the incisor area.

RESULTS

The results showed that the prevalence of S mutans on incisor brackets was higher than that of S sobrinus, and the maxillary incisor brackets were colonized by both cariogenic streptococci to a somewhat higher degree than were the mandibular brackets. The prevalence of S mutans was 50.0% on the maxillary incisor brackets and 33.8% on the mandibular incisor brackets, but that of S sobrinus was 17.5% and 15.0%, respectively. At least 1 species of cariogenic streptococci was detected on the incisor brackets of 51 subjects (63.7%). However, the prevalence of cariogenic streptococci was not significantly associated with the oral hygiene indexes at debonding.

CONCLUSIONS

Cariogenic streptococci can adhere to orthodontic brackets. Careful hygiene control around orthodontic brackets is important.

In vitro anti-cariogenic activity of dichloromethane fraction from Rheum undulatum L. root

This study aimed to evaluate in vitro effects of Rheum undulatum L. root on the development of dental caries, especially its effects on viability, dental plaque formation, and glycolytic acid production of Streptococcus mutans and Streptococcus sobrinus. Methanol extract of Rheum undulatum L. root and its fractions were prepared and tested. Among the test extract and fractions, dichloromethane fraction (DF) showed the most active antibacterial activity (inhibition zone: 13-17 mm) against S. mutans and S. sobrinus in a disc diffusion method. Minimal inhibitory concentrations (MICs) of DF against these bacteria ranged from 0.25 to 0.5 mg/mL. Furthermore, DF significantly inhibited the caries-inducing factors of these bacteria. At sub-MIC levels, DF inhibited in vitro dental plaque formation by S. mutans and S. sobrinus (IC50= 0.079 and 0.142 mg/mL, respectively), which was caused, in part, by the inhibitory effect on the activity of glucosyltransferases. A significant reduction of glycolytic acid production was found at the concentration as low as 0.032 mg/mL for S. mutans and 0.063 mg/mL for S. sobrinus. The possible bioactive compounds that are inducing in vitro anti-cariogenic activity of DF are unknown. Based on the preliminary phytochemical analysis, the activity of DF may be related to the presence of anthraquinones, cardiac glycosides, coumarines, sterols/terpenes, and phenolics. These results indicate that DF is probably useful for the control of dental plaque formation and subsequent dental caries development.

Differentiation of Streptococcus mutans and Streptococcus sobrinus via genotypic and phenotypic profiles from three different populations

Routine identification of Streptococcus mutans and Streptococcus sobrinus is generally based upon growth on various selective media, colony morphology and biochemical characteristics. We examined various approaches of differentiating these two species through a combination of the conventional phenotypic methodology with chromosomal DNA fingerprint (CDF) and arbitrarily primed polymerase chain reaction (AP-PCR) methods. Initially, ten ATCC type strains and 20 randomly selected clinical isolates of mutans streptococci (MS) were characterized and grouped into two major types based on patterns generated by the CDF using HaeIII digestion. The CDF's patterns with restriction fragments equal to or greater than 6.6 kb were defined as the CDF-1 group. The CDF's patterns with restriction fragments less than 6.6 kb were defined as the CDF-2 group. Both groups were then examined for biotype, serotype, and composition of DNA via thermal denaturation. AP-PCR was applied and evaluated for the capability of delineating S. mutans from S. sobrinus strains. Results of this study showed that all CDF-1 strains fit within a G+C range of 36.2% to 42.2%, whereas the CDF-2 strains had a G+C range of 45.8% to 47.0%. The serotyping assay exhibited 100% sensitivity, 90% specificity and 86.7% agreement with the CDF. The biotyping assay presented the poorest specificity (38.5%), indicating the highest variability. The capability of AP-PCR in differentiation of S. mutans from S. sobrinus was comparable to the CDF method, suggesting that either of these two approaches can and may serve as a viable alternative method to serotyping or biotyping of MS.

Influence of (S)-ketoprofen and fluoride on caries in rats

OBJECTIVE

Non-steroidal anti-inflammatory agents (e.g., ketoprofen) used topically appear to be effective in reducing bone loss in the ligature model of periodontitis. Ketoprofen, in common with some food preservatives, e.g., benzoate and sorbate, is a weak acid. Fluoride, too, may behave as a weak acid and, similar to the other agents, may exert antibacterial effects. The purpose of the present study was to determine whether a combination of (S)-ketoprofen, an enantiomer of ketoprofen, alone or in combination with fluoride, would suppress Streptococcus sobrinus populations and reduce the incidence of dental caries in rats.

MATERIALS AND METHODS

Toothpastes containing ketoprofen and/or monofluorophosphate were applied to the teeth of six groups of 20 rats twice daily for 5 weeks.

RESULTS

Fewest S. sobrinus were found in the group treated with a paste containing 3% (S)-ketoprofen + 0.1% F. This group also displayed the lowest incidence of smooth surface caries of all groups. Severity of sulcal surface caries was also lowest in this group.

CONCLUSIONS

Results from this study show that the (S) enantiomer of ketoprofen enhances the caries protective effect of fluoride. It is conceivable that this combination could be effective in combating the two most common maladies of the mouth; periodontal disease and dental caries.

Influence of lead on the cariostatic effect of fluoride co-crystallized with sucrose in desalivated rats

OBJECTIVE

Results from previous studies have shown that pre- and perinatal exposure to lead enhances susceptibility of rats to development of dental caries. A possible explanation for this phenomenon may be that lead complexes with fluoride and renders F insoluble and unable to exert its cariostatic effects.

MATERIALS AND METHODS

Thus, to explore this hypothesis, 48 desalivated Sprague-Dawley rats were placed in a König-Höfer programmed feeder and received 17 meals of powdered sucrose daily, and water ad libitum as follows: group (1) plain sucrose and sterile distilled water (SDW); (2) sucrose containing 15 ppm F and SDW; (3) sucrose containing 15 ppm F and 10 ppm Pb water; (4) sucrose containing 15 ppm F and 25 ppm Pb water.

RESULTS

The highest smooth-surface, sulcal surface caries and severity scores were observed in group I. Animals that were exposed to fluoride showed reduced smooth-surface caries and severity scores. S. sobrinus counts did not differ among the groups.

CONCLUSION

Lead did not interfere with the protective effect of fluoride in the conditions of the present study.

Response to Seow: biological mechanisms of early childhood caries

For more than three decades, it has been recognized that dental caries is an infectious and transmissible disease in which diet plays a key role. Nevertheless, in treating patients with early childhood caries, scant attention is placed on exploring the source of infection and the prevalence of caries in other family members. Results from studies conducted in animals clearly show that the virulence of mutans streptococci can be enhanced by a highly cariogenic environment. For example, offspring from a highly caries-active dam develop significantly more caries than pups from a low caries-active dam. Considerable attention has been placed on the role of the nursing bottle in early childhood caries. Milk and some infant formulas do not promote caries and the role of the remainder of the diet has been largely ignored. The nursing bottle can effectively block salivary access to tooth surfaces, thereby increasing the cariogenicity of any food remaining in the mouth. Recent evidence shows that salivary gland function is impaired by iron deficiency and by prenatal exposure to lead. Clearly, early childhood caries is a complex disease that requires careful and extensive investigation.

Effects of iron salts in sucrose on dental caries and plaque in rats

Anaemia caused by iron deficiency and dental caries are still among the most prevalent diseases in some developing countries. Anaemia can be prevented by iron fortification of food. Previous studies demonstrated that iron-sucrose, which has been used for prevention of anaemia, reduces the incidence of caries in rats. The aim of the present study was to compare the influence of ferrous sulphate and ferric glycerophosphate co-crystallized with sucrose on the incidence of dental caries in rats. Forty-eight desalivated rats were caged in a programmed feeder and received their essential nutrition by gavage. The animals were fed 17 meals per day at hourly intervals of 88 parts/10(6) Fe++ or Fe co-crystallized with sucrose. Plain sucrose and calcium glycerophosphate with sucrose were used as control groups. Both ferric- and ferrous-sucrose meals reduced the incidence of smooth-surface and sulcal caries in rats. Stain formation, organic acid production and acidogenic activity of dental plaque in animals receiving iron-sucrose meals were also investigated. Ferric glycerophosphate did not induce extrinsic staining on the tooth surface. The concentration of organic acids did not differ significantly among the groups. The acidogenic activity of plaque in animals receiving either of the iron-sucrose meals tended to be lower than that of the control groups. The possibility that iron-sucrose might reduce the prevalence of two major public health problems, dental caries and anaemia, makes this preventive approach extremely attractive for additional investigation.

Influence of fluoride co-cystallized with sugar on caries development in desalivated rats

Previous studies have shown that fluoride (F) administered concomitantly with sucrose in drinking water, in the diet, or alone is an effective cariostatic agent. The purpose of the present study was to determine the minimum concentration of F co-crystallized with sugar that may be used to prevent dental caries in rats subjected to a severe cariogenic challenge. Desalivated Sprague-Dawley rats, infected with Streptococcus sobrinus, were placed in a König-Höfer programmed feeder. The rats received 17 meals daily for 21 days as follows: group (1) sucrose and sterile distilled water (s.d.w.); (2) sucrose and 1 part/10(6) F-water; (3) 1 part/10(6) F-sucrose and s.d.w.; (4) 4 parts/10(6) F-sucrose and s.d.w.; (5) 8 parts/10(6) F-sucrose and s.d.w.; (6) sucrose and 10 parts/10(6) F-water. Essential nutrition was administered by gavage. At death, blood was collected from each animal and one-half of the lower jaw was sonicated in 0.9% saline solution for microbial assessment and F analysis. Keyes smooth-surface and sulcal caries scores were significantly lower in the groups that received 10 parts/10(6) F-water and 8 parts/10(6) F-sucrose than in all other groups. The F concentration in the jaw suspension and plasma were significantly higher in the 10 parts/10(6) F-water and the 8 parts/10(6) F-sucrose groups than in all other groups. The total cultivable flora and Strep. sobrinus populations were lowest in F groups but this did not reach statistical significance. It is concluded that 8 parts/10(6) F co-crystallized with sucrose reduces the cariogenic potential of sugar as effectively as 10 parts/10(6) F in water, that is as little as 1 part/10(6) in sucrose has a significant effect, and that this cariostatic action is related to the amount of F in the oral environment.

Effects of copper, iron and fluoride co-crystallized with sugar on caries development and acid formation in deslivated rats

The purpose was to explore the effects of combinations of copper, iron and fluoride (Cu, Fe and F) incorporated in sucrose by co-crystallization on caries development in the deslivated rat model and to examine acid formation by bacteria in the rat mouth. Ninety-six Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and desalivated when aged 26 days. Eight groups were placed in a König-Höfer programmed feeder and received 17 meals daily at hourly intervals, and essential nutrition (NCP No. 2) by gavage twice daily for 21 days. The groups received (1) plain sucrose, (2) F (8 parts/10(6)) co-crystallized with sucrose, (3) Fe (88 parts/10(6)) sucrose, (4) Cu (75 parts/10(6)) sucrose, (5) Cu + F sucrose, (6) Cu + L Fe sucrose, (7) F + Fe sucrose, and (8) Cu + Fe + F sucrose. At death the jaws were removed and sonicated in 0.9% saline solution for microbial assessment. In addition, organic acid assays were performed for each animal. Keyes smooth-surface and sulcal caries scores were lowest in the Cu + Fe + F sucrose group, but not statistically significantly different from those of the other Cu groups. The numbers of Strep. sobrinus found in the groups that received Cu, Cu + Fe, Cu + F, F + Fe and Cu + Fe + F sugar were lower than in the control group. Lactic acid was found in lower concentrations in Fe, Cu, Cu + F, Cu + Fe and F + Fe groups than in the other groups. It appears that combinations of Cu; Fe and F co-crystallized with sugar may have an additive effect in reducing the cariogenic potential of sugar by affecting lactic acid formation and reducing bacterial colonization.

Cariogenicity of Streptococcus mutans strains with defects in fructan metabolism assessed in a program-fed specific-pathogen-free rat model

To define the role of dental plaque fructans and the enzymes involved in their metabolism in the initiation and progression of dental caries, we constructed otherwise-isogenic mutants of Streptococcus mutans defective in the ability to synthesize fructans, to degrade fructans, or to do both. The cariogenic potential of these organisms was evaluated in a specific-pathogen-free rat model in which the feeding patterns of the animals were controlled by means of a König-Hofer programed feeder. Specifically, rats were infected with wild-type S. mutans UA159 or derivatives of this strain which contained an insertionally-inactivated fructanase (fruA) gene, fructosyltransferase (ftf) gene, or which had both genes inactivated. The animals were fed 17 meals per day of Diet 2000 containing 56% sucrose at 70-minute intervals for five weeks, and caries experience was evaluated. Animals infected with S. mutans with a mutated fruA gene only had statistically significant decreases in sulcal caries severity. Such a decrease was not observed in previous studies with ad libitum-fed animals (Wexler et al., 1992). The manifestation of diminished virulence in the programmed feeding model, but not in ad libitum-fed animals, supports the concept that the primary contribution of FruA to virulence is through the utilization of fructans storage polysaccharides. Animals infected with strains carrying the ftf mutation or simultaneous mutations in ftf and fruA did not display decreased virulence, perhaps indicating that sucrose utilization pathways may compete for substrate in vivo, or that accumulation of fructans may affect the ecology or the physicochemical characteristics of dental plaque in such a way as to reduce its cariogenic potential. The results of this study also emphasize that the contribution of a particular virulence determinant to the caries process may be highly dependent on the experimental design, feeding regimen and diet, and the presence or absence of other enzymatic activities.

Simultaneous caries induction and calculus formation in rats

Weanling specific pathogen-free Osborne-Mendel rats were fed a high-calcium, high-phosphorus diet with various levels of sucrose and inoculated with Streptococcus sobrinus strain 6715-13WT and Actinomyces viscosus strain OMZ-105 in order to determine whether calculus and caries could develop simultaneously. Rats consumed diets designated RC-16-5, RC-16-25, or RC-16-50 which partially replaced the corn starch component with progressively higher levels of sucrose, thus, to 5, 25, or 50% sucrose. In general, bacterial recoveries of A. viscosus declined with higher sucrose content of the diet, but a pattern of recovery for S. sobrinus was less clear with respect to dietary sucrose. S. sobrinus, however, was recovered at higher percentages from the tooth surface flora at the later two of three sampling dates. Most calculus--identified by the brittle quality, staining characteristics, and apatitic x-ray diffraction patterns of tooth surface deposits--was formed on the maxillary molars, and most carious lesions occurred on mandibular molars. While there was minimal association of the calculus score with the amount of sucrose in the diet, calculus scores increased greatly from 23 to 43 days after infectious challenge. Caries scores, of both fissure and smooth surfaces, by contrast, increased in a dose-response fashion with increasing dietary sucrose and with time. It is thus possible to induce calculus formation and caries simultaneously in specific pathogen-free Osborne-Mendel rats consuming a high-calcium and -phosphorus diet conducive to calculus formation and containing sucrose.(ABSTRACT TRUNCATED AT 250 WORDS)