Studying biofilm formation of mutans streptococci.
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Bacterial Adhesion↗
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Salivary microbiota levels in relation to periodontal status, experience of caries and miswak use in Sudanese adults.
OBJECTIVES: The purpose of the present investigation was to assess the salivary levels of 25 oral bacteria in relation to periodontal status and experience of caries, and to compare the levels of these bacteria between habitual miswak and toothbrush users in adult Sudanese subjects. MATERIAL AND METHODS: The study subjects consisted of 56 individuals with age range 19-53 years (mean 35.2 years) and included 30 miswak and 26 toothbrush users. The periodontal status and presence of dental caries were assessed clinically. Whole saliva was collected from all subjects, and the levels of 25 selected bacterial species in saliva were assessed by the checkerboard DNA-DNA hybridization method using whole genomic DNA probes. RESULTS: A high percentage of the subjects had detectable levels (> or = 105 bacterial cells) of several bacterial species in saliva. Between 12% and 16% of the subjects showed high (> or = 106 cells) salivary levels of the periodontitis-associated bacteria A. actinomycetemcomitans, P. melaninogenica, P. intermedia, C. rectus and E. corrodens, whereas only two (3.6%) and four (7.1%) subjects had high levels of P. gingivalis and F. nucleatum, respectively. There were no significant differences in the levels of all or most bacterial species by age group, gender or periodontal status. Presence of > or = 105 L. acidophilus bacterial cells in saliva was associated with high caries scores (p = 0.02). There were significantly higher levels of A. actinomycetemcomitans, P. melaninogenica, C. rectus, P. micros, V. parvula, S. mutans, S. anginosus, A. israelii, C. sputigena, and C. gingivalis, and significantly lower levels of P. intermedia, F. nucleatum, S. sputigena, E. corrodens, L. acidophilus, S. sanguis, S. salivarius, S. oralis, and S. mitis in the miswak than in the toothbrush group. CONCLUSIONS: : The findings suggest that miswak may have a selective inhibitory effect on the level of certain bacteria in saliva, particularly several oral streptococci species. This is the first report that the checkerboard DNA-DNA hybridization method can be useful for assessing the levels of a wide range of bacterial taxa in saliva.
Adult↗
Xylitol-induced elevated expression of the gbpC gene in a population of Streptococcus mutans cells.
Xylitol possesses a unique property distinct from the other caries-preventive sweeteners. This sugar alcohol cannot be metabolized to acids but is taken up by Streptococcus mutans and accumulated as a toxic sugar-phosphate in the cells, resulting in growth inhibition. Due to the accumulation, xylitol induces biological responses including the emergence of xylitol-insensitive populations. Therefore, we expected another response induced by xylitol and found a new phenomenon, that cells repeatedly cultured in the presence of xylitol evolved into those exhibiting an elevated dextran-dependent aggregation phenotype. This phenotype was found to result from expression of the gbpC gene, which was previously reported to be expressed only under certain stress conditions. Construction of a Strep. mutans isogenic mutant carrying the gbpC::lacZ fusion gene indicated that gbpC expression of cells repeatedly cultured in the presence of xylitol was elevated 20-fold. DNA transfer experiments indicated that this phenotypic change did not appear to be due to a mutation. These cells also exhibited decreased adhesion to glass surfaces when grown in the presence of sucrose. This may be one of the ways by which some populations of Strep. mutans are removed from dental plaques.
Adaptation, Physiological↗
Antimicrobial activity of silver nitrate against periodontal pathogens.
Metal ions were evaluated as potential antimicrobial agents suitable for local delivery in the oral cavity for the treatment of periodontitis. Silver nitrate, copper chloride, and zinc chloride were tested for antimicrobial activity in in vitro killing assays conducted in phosphate buffered saline with a series of oral bacteria including gram-negative periodontal pathogens and gram-positive streptococci. Copper and zinc salts failed to exhibit strong and consistent activity against periodontal pathogens. In contrast, silver at a concentration of 0.5 microg/mL produced a 3 log10 reduction in colony forming units (CFU)/mL or greater against all periodontal pathogens tested including Porphyromonas gingivalis, Prevotella intermedia, Prevotella denticola, Bacteroides forsythus, Fusobacterium nucleatum vincentii, Campylobacter gracilis, Campylobacter rectus, Eikenella corrodens, and Actinobacillus actinomycetemcomitans. In comparison, substantially higher concentrations of silver nitrate failed to kill oral streptococci. A silver nitrate concentration of 25 microg/mL produced log10 reductions in CFU/mL of 3.5-5 in killing assays performed in human serum against P. gingivalis, demonstrating the ability of silver to retain activity in a biological medium similar to that encountered in vivo in the periodontal pocket. These results identify silver nitrate, an antimicrobial that may possess advantages over traditional antibiotics, as a potential agent for controlled release local delivery in the oral cavity for the treatment of periodontitis.
Administration, Topical↗
The use of a caries detector dye during cavity preparation: a microbiological assessment.
During cavity preparation conventional tactile and optical criteria are used to assess the caries status of the enamel-dentine junction, cavity preparation being considered complete when this area is hard to a sharp probe and stain free. In the present study 201 cavities were prepared under rubber dam. When caries removal was considered complete using the conventional tactile and optical criteria, a caries detector dye (1% acid red in propylene glycol), which is claimed to stain 'infected' tissue red, was applied. Fifty-two per cent of cavities showed caries dye stain in some part of the enamel-dentine junction. Subsequent microbiological sampling of dye-stained and dye-unstained sites resulted in the recovery of low numbers of bacteria and revealed no difference in the level of infection of the two sites. It is concluded that the conventional tactile and optical criteria are satisfactory assessments of the caries status of tissue during cavity preparation and that subsequent use of a caries detector dye on hard and stain-free dentine will result in unnecessary tissue removal.
Adult↗
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.
Carbon Radioisotopes↗
Demonstration of identical strains of mutans streptococci within Chinese families by genotyping.
The aim of this study was to investigate the intra-familial distribution of mutans streptococci in some Chinese families. Eighteen families consisting of mother, father and a 3-yr-old child without any older siblings participated. Clinical examination and interview were performed to obtain information about level of mutans streptococci in saliva, caries prevalence scored by DMFT or deft, general health, diet regimens, breast-feeding time, principal caretaker of the child and the parents' profession. At the same appointment, two pooled plaque samples from each subject were collected with the tips of sterile tooth picks. From these plaque samples, mutans streptococci were isolated on MSB-agar plates and identified by serotyping. Pure isolates were obtained from all subjects of 11 families. These isolates were genotyped using restriction endonuclease HaeIII. The results showed that in 4 families the mothers shared genotype with the child, and in 3 families it was the father and the child who harboured a similar genotype. In 2 families, all subjects harboured an identical genotype. Further, the spouses in one parental pair showed an identical genotype, and, finally, in one family all subjects harboured their unique genotypes. None of the investigated factors could explain the differences in the intra-familial distribution of mutans streptococci. The pattern of similar genotypes in these Chinese families differs from that reported for western families.
Adult↗
Recolonisation pattern of mutans streptococci after suppression by three different modes of chlorhexidine gel application.
Clinical studies have shown conflicting results for the reduction of approximal caries when chlorhexidine gel has been applied either in trays or by flossing. To investigate whether these modes of treatment affect the colonization of mutans streptococci (MS) differently, we quantified MS in saliva and on various tooth surfaces before and after a single chlorhexidine gel application. Twenty-one schoolchildren (15-16 yr old), with high numbers of salivary MS, were randomised into three groups. The subjects were treated with a 1% chlorhexidine gel applied either by: 1) interdental flossing; 2) individually designed mouth trays; or 3) a combination of polishing and flossing. Analysis of saliva and of dental plaque from 12 sites over an 8-wk period showed a greater reduction of both salivary MS counts and total number of colonised sites in the tray group than in the flossing group. The effect on MS in the polishing-flossing group approached that obtained in the tray group. In the interdental areas, more sites had no detectable MS (score 0) after tray treatment than after flossing, whereas the reduction of heavily colonised sites (scores 3+/-4) was higher in the flossing group. The reappearance of sites with score 3+/-4 after the gel treatment was more rapid in the flossing group than in the other two groups. In conclusion, the results showed a transient reduction of MS colonisation by all three methods, and that the application of the chlorhexidine gel both in mouth trays or as a combination of polishing and flossing was more effective in reducing the MS population than flossing alone.
Administration, Topical↗
Effects of bovine immune and non-immune whey preparations on the composition and pH response of human dental plaque.
Colostral products from non-immunized cows (CP) and cows immunized with mutans streptococci (IP) were used as mouth rinses in a short-term human study. The acidogenic potential of the products was tested and found to be negligible in vivo before application to subsequent rinsing tests. At first, all the participants received a professional tooth cleaning, after which they rinsed with one of the solutions (IP; CP; water) three times per day for 3 d. After each rinsing period, the resting pH and decrease in plaque pH after sucrose challenge were determined, the amount of plaque was estimated, and all available plaque was collected. No significant differences were recorded in the composition or in the amounts of accumulated plaque. The resting pH values of plaques with low "innate" pH were increased after the IP rinsing period. Surprisingly, the lowest pH values after the sucrose challenge were recorded in IP plaques. The number of cultivable facultative flora or total streptococci were not affected by different rinsings, but the relative number of mutans streptococci significantly decreased after the IP rinsing period when compared to the CP period. Thus, the short term rinsing indicates favourable effects of bovine immune whey on human dental plaque.
Adult↗
Antibacterial properties of dentin bonding systems, polyacid-modified composite resins and composite resins.
This study examined the antibacterial activities of the bonding systems Syntac, EBS and Scotchbond 1, the polyacid-modified composite resins Hytac and Compoglass, and the composite resins Tetric, Z100 and Scalp-it. They were evaluated using the cariogenic bacteria Streptococcus mutans, Lactobacillus salivarius, Streptococcus sorbinus and Actinomyces viscosus in vitro with a modified cylinder drop plate agar diffusion assay. All adhesives of the dentin bonding systems and the polyacid-modified composite resins exhibited various degrees of antibacterial activity against all of the test bacteria. On the contrary, composite resins did not affect bacterial growth. The data suggest that the use of these adhesives and polyacid-modified composite resins may reduce the consequences of microleakage owing to their antibacterial properties.
Actinomyces viscosus↗
High-sucrose diet reduces defensive reactions of the pulpo-dentinal complex to dentinal caries in young rats.
The significance of systemic dietary effects on the response of the pulpo-dentinal complex to dentinal caries was examined. Weanling rats were divided into high sucrose or control diet groups both with and without cariogenic bacterial inoculation. At the onset, tetracycline was injected to mark the dentin formation during the experiment. After 5-6 week, mandibular molars were sectioned sagittally. The areas of dentin formed during the experiment and those of dentinal caries were quantified separately in the first and second molars. In the control diet groups the area of dentin was significantly greater under carious fissures, whereas in the high sucrose diet groups the area of dentin formed did not differ between intact and carious fissures. The high sucrose diet resulted in a significantly smaller area of dentin formation than did the control diet. The high sucrose diet with cariogenic bacterial inoculation resulted in the greatest area of dentinal caries. With the control diet a positive response against dentinal caries occurs, but the high dietary sucrose content impairs the defensive reactions of pulpo-dentinal complex against dentinal caries. These findings add further evidence of the importance of the local endogenous factors of caries progression.
Analysis of Variance↗
Composition of the salivary microflora during habitual consumption of fluoridated milk.
The aim was to evaluate the effect of habitual consumption of fluoridated milk on the composition of the salivary microflora. The study group comprised 20 healthy schoolchildren and young adults with a mean age of 13.6 years and the investigation had a randomized double-blind crossover design with a washout period of 1 month. After professional tooth-cleaning at baseline, the subjects were supplied with either fluoridated (250 mL, 5 ppm F) or non-fluoridated milk for one daily intake during a period of 4 weeks. Salivary samples were collected immediately before tooth-cleaning and after 1, 2, and 4 weeks, respectively. The samples were immediately cultivated for total viable counts, oral streptococci, mutans streptococci, lactobacilli, and actinomyces spp. Bacterial counts were logarithmically transformed before statistical evaluation using ANOVA. No significant alterations of the salivary microflora were found during any of the milk regimens compared with baseline. There was a slight reduction in the proportion of mutans streptococci after 2 and 4 weeks during consumption with fluoridated milk but the difference failed to reach statistical significance. In conclusion, this study was unable to disclose any significant alteration of the composition of the salivary microflora following daily intake of fluoridated milk.
Actinomyces↗
Validation and inter-examiner agreement of mutans streptococci levels in plaque and saliva of 10-year-old children using simple chair-side tests.
Since there are few validation studies of chair-side tests of oral mutans streptococci, we compared a commercially available strip test with the conventional laboratory assay. Two plaque samples obtained from the mesial surfaces of the upper right and lower left permanent molars of sixty-five 10-year-old children (boys = 38, girls = 27) were cultured and incubated using chair-side site strip tests (Dentocult SM, Orion Diagnostica). Two plaque sampling tools, namely dental floss and micro-brush, were compared, and inter-examiner agreement between recordings of three examiners was assessed. Paraffin-stimulated saliva was then collected for laboratory and chair-side assays. The plaque and saliva chair-side tests correlated well with each other (Spearman rho, r = 0.72) and with the laboratory method, showing coefficients of 0.76 and 0.80 for saliva and plaque, respectively. Compared to the laboratory method, the sensitivity (Sn), specificity (Sp), accuracy (A), and kappa (K) values of the salivary and plaque chair-side tests were 0.63, 0.75 (Sn), 0.93, 0.90 (Sp), 0.82, 0.85 (A), and 0.58, 0.66 (K), respectively. Agreement between the two plaque sampling techniques was good (0.91). Inter-examiner agreement of plaque scores ranged between 0.65 and 0.86 when all density categories were analysed separately; when dichotomized into low and high categories, complete agreement was found. Agreement between the plaque and saliva chair-side tests and the laboratory salivary assay was good, and in terms of sensitivity, accuracy, and kappa values, the site strip plaque test surpassed the salivary chair-side test.
Child↗
Levels of mutans streptococci and lactobacilli in plaque on aged restorations of an ion-releasing and a universal hybrid composite resin.
The purpose of this in vivo study was to evaluate the cariogenic microflora of plaque on aged restorations of a hydroxyl, fluoride, and calcium ion-releasing composite resin (IRCR) (Ariston pHc), and to compare it intra-individually with a universal hybrid composite resin and enamel. Each of 19 subjects received one proximal restoration of the IRCR, one proximal universal hybrid composite resin restoration (CR) and each subject had one non-filled proximal enamel control surface to make intra-individual comparisons possible. To avoid peak ion releases from the materials, aged restorations were studied. Plaque was collected from 57 surfaces using sterile applicator tips. Samples were cultured to determine the numbers of mutans streptococci, lactobacilli, and total microorganisms. The relative numbers for mutans streptococci (% of total bacteria) were: IRCR 0.59%, CR 0.40%, enamel 0.22%. Two outliers were found in the IRCR group. Excluding these outliers resulted in a relative number of 0.33%. Lactobacilli were detected in the plaque from only 9 surfaces and at very low relative proportions for all three surfaces: 0.01%. The enamel surfaces showed the lowest relative numbers of mutans streptococci and lactobacilli, but the differences were not significant. It can be concluded that the ion release of the IRCR did not influence the growth of cariogenic microorganisms in dental plaque.
Aged↗
Effect of xylitol-containing chewing gums on interdental plaque-pH in habitual xylitol consumers.
OBJECTIVE: The aim was to investigate the effect of high and low amounts of xylitol on the interdental plaque-pH, directly and after sucrose challenge, in schoolchildren with habitual consumption. MATERIAL AND METHODS: The study group consisted of 11 healthy children (10-15 years) with low caries risk and the experiment had a single-blind crossover (Latin square) design. After a 2-week run-in period with a daily 4.0 g xylitol intake, the children were subjected to single-dose exposures of chewing gums with (i) paraffin (CTR; no xylitol), (ii) low-dose xylitol (LX; 2.0 g xylitol), and (iii) high-dose xylitol (HX; 6.0 g xylitol) in a randomized order separated by a washout period of 1 week. Samples of chewing-stimulated whole saliva were collected prior to and after the experimental period for determination of bacterial counts. The outcome measures were in situ plaque-pH (micro-touch method) and area under the pH curve (AUC). RESULTS: The AUC was significantly greater (p < 0.05) in the HX group compared to the LX and control groups during the first 5 min after chewing. After a 10% sucrose rinse, the interdental plaque-pH dropped in all groups but the HX regimen displayed significantly less reduction 0-5 min after chewing (p < 0.05). No significant alterations of the total viable counts or mutans streptococci levels in saliva were disclosed during the 4-week experimental period. CONCLUSIONS: The present results suggested that a high single dose of xylitol had a short and limited beneficial effect on interdental plaque-pH in habitual xylitol consumers, while a low single dose, resembling normal chewing gum use, did not differ from the control.
Adolescent↗
Extraction, assay, and analysis of antimicrobials from plants with activity against dental pathogens (Streptococcus sp.)
Many dental and periodontal diseases are largely a question of bacterial etiology. Dental caries develop due to an increase of strongly acidogenic and aciduric gram-positive bacteria while common forms of periodontal disease are linked to anaerobic gram-negative bacteria in subgingival plaque. Many plants and plant-derived antimicrobial components are used in folklore therapeutics for the treatment of periodontal disorders and for the purposes of oral hygiene. Some have been evaluated for possible use in modern medicine, while thousands of other potentially useful/plants have not been tested. In this study, we evaluated the feasibility of screening for antibacterials isolated from plants with activity against three representatives of oral streptococci. We developed and tested the following methodologies: (1) Extraction of antibacterial components from plants; (2) Assays for antibacterial activity; (3) Chromatographic methods for initial analysis of compounds of interest. The screening process for plant antimicrobials consisted of extraction of plant material and assay of antibacterial activity using a spotting test with the selected oral streptococci as indicator strains. In addition, we developed chromatographic procedures that allow characterization and optimization of initial isolation steps. Depending on the indicator microorganisms used, the screening assay can target additional pathogens including other streptococci (group A and B, and pneumococci) and periodontal pathogens such as Porphyromonas. Also, we noted that the activity of some extracts varied against different oral bacteria. Our conclusion, supported by extensive data, was that the screening for antimicrobials from plants is a feasible approach to the identification of natural compounds with antimicrobial properties against dental pathogens.
Anti-Bacterial Agents↗
Whole-cell protein electrophoretic analysis of viridans streptococci: evidence for heterogeneity among Streptococcus mitis biovars.
One hundred reference strains representing all species belonging to the different phylogenetic lineages of the viridans streptococci were examined by means of one-dimensional whole-organism protein electrophoresis. For most of the species examined, multiple strains characterized by DNA-DNA hybridization were included and, wherever described, representatives of different biochemical variants were analysed. Most species were clearly differentiated. The data support the viewpoint that members of the Streptococcus anginosus group constitute a single species and indicate that Streptococcus mitis biovar 2 is a heterogeneous taxon comprising strains from several streptococcal species.
Bacterial Proteins↗
Inhibitory effects of cranberry juice on attachment of oral streptococci and biofilm formation.
Cranberry juice is known to inhibit bacterial adhesion. We examined the inhibitory effect of cranberry juice on the adhesion of oral streptococci strains labeled with [3H]-thymidine to saliva-coated hydroxyapatite beads (s-HA). When the bacterial cells were momentarily exposed to cranberry juice, their adherence to s-HA decreased significantly compared with the control (P < 0.01). Their hydrophobicity also decreased dependently with the concentration of cranberry juice. We also evaluated the inhibitory effect of cranberry juice on biofilm formation. By using a microplate system, we found that the high molecular mass constituents of cranberry juice inhibited the biofilm formation of the tested streptococci. The inhibitory activity was related to the reduction of the hydrophobicity. The present findings suggest that cranberry juice component(s) can inhibit colonization by oral streptococci to the tooth surface and can thus slow development of dental plaque.
Adult↗