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Background: Streptococcus mutans and Streptococcus sobrinus are Gram-positive bacteria involved in the development of dental caries, as they are able to form biofilms on tooth enamel, ferment sugars into acids, and survive under acidic conditions. This ultimately leads to a local lowering of the pH value on the tooth surface, which causes enamel cavities., Hypothesis: One measure to reduce caries is to limit the growth of cariogenic bacteria by using two anti-bacterial agents with different mechanisms of action. The hypothesis of this study was that the anti-bacterial activity of ω-6 polyunsaturated arachidonic acid (AA) against S. mutans and S. sobrinus can be enhanced by the sesquiterpene alcohol trans, trans-farnesol (t,t-farnesol)., Methods: The anti-bacterial activity of single and combined treatment was determined by the checkerboard assay. Bacterial viability was assessed by live/dead SYTO 9/propidium iodide (PI) staining on flow cytometry. Anti-biofilm activity was determined by MTT metabolic assay, crystal violet staining of biofilm biomass, SYTO 9/PI staining by spinning disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM)., Results: t,t-Farnesol lowered the minimum inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) of AA at sub-MICs. AA reduced the metabolic activity of preformed mature biofilms, while t,t-farnesol had no significant effect. The enhanced anti-bacterial effect of the combined t,t-farnesol/AA treatment was further evidenced by increased PI uptake, indicating membrane perforation. The enhanced anti-biofilm effect was further verified by SDCM and HR-SEM. Gene expression studies showed reduced expression of some biofilm-related genes., Conclusions: Altogether, our study suggests a potential use of the two naturally occurring compounds arachidonic acid and t,t-farnesol for preventing biofilm formation by the cariogenic bacteria S. mutans and S. sobrinus . These findings have implications for caries prevention.

Streptococcus mutans is a cariogenic bacterium in the oral cavity involved in plaque formation and dental caries. The endocannabinoid anandamide (AEA), a naturally occurring bioactive lipid, has been shown to have anti-bacterial and anti-biofilm activities against Staphylococcus aureus . We aimed here to study its effects on S. mutans viability, biofilm formation and extracellular polysaccharide substance (EPS) production. S. mutans were cultivated in the absence or presence of various concentrations of AEA, and the planktonic growth was followed by changes in optical density (OD) and colony-forming units (CFU). The resulting biofilms were examined by MTT metabolic assay, Crystal Violet (CV) staining, spinning disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM). The EPS production was determined by Congo Red and fluorescent dextran staining. Membrane potential and membrane permeability were determined by diethyloxacarbocyanine iodide (DiOC2(3)) and SYTO 9/propidium iodide (PI) staining, respectively, using flow cytometry. We observed that AEA was bactericidal to S. mutans at 12.5 µg/mL and prevented biofilm formation at the same concentration. AEA reduced the biofilm thickness and biomass with concomitant reduction in total EPS production, although there was a net increase in EPS per bacterium. Preformed biofilms were significantly affected at 50 µg/mL AEA. We further show that AEA increased the membrane permeability and induced membrane hyperpolarization of these bacteria. AEA caused S. mutans to become elongated at the minimum inhibitory concentration (MIC). Gene expression studies showed a significant increase in the cell division gene ftsZ . The concentrations of AEA needed for the anti-bacterial effects were below the cytotoxic concentration for normal Vero epithelial cells. Altogether, our data show that AEA has anti-bacterial and anti-biofilm activities against S. mutans and may have a potential role in preventing biofilms as a therapeutic measure.

Objectives: In this study, we aimed to develop a novel, sustained release varnish (SRV) for voice prostheses (VP) releasing chlorhexidine (CHX), for the prevention of biofilm formation caused by the common oral bacteria Streptococcus mutans on VP surfaces., Methods: This study was performed in an in vitro model as a step towards future in vivo trials. VPs were coated with a SRV containing CHX (SRV-CHX) or SRV alone (placebo-SRV) that were daily exposed to S. mutans. The polymeric materials of SRV were composed of ethylcellulose and PEG-400. Biofilm formation was assessed by DNA quantification (qPCR), crystal violet staining, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and kinetics experiments., Results: The amount of DNA in the biofilms formed by S. mutans on VP surfaces coated once with SRV-CHX (1.024 ± 0.218 ng DNA/piece) was 58.5 ± 8.8% lower than that of placebo-SRV-coated VPs (2.465 ± 0.198 ng DNA/piece) after a 48-h exposure to S. mutans (p = 0.038). Reduced biofilm mass on SRV-CHX-coated VPs was visually confirmed by CLSM and SEM. CV staining of SRV-CHX single-coated VPs that have been exposed to S. mutans nine times showed a 98.1 ± 0.2% reduction in biofilm mass compared to placebo-SRV-coated VPs (p = 0.003). Kinetic experiments revealed that SRV-CHX triple-coated VPs could delay bacterial growth for 23 days., Conclusions: Coating VPs with SRV-CHX has an inhibitory effect on biofilm formation and prevents bacterial growth in their vicinities. This study is a proof-of-principle that paves the way for developing new clinical means for reducing both VPs' bacterial biofilm formation and device failure., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: Streptococcus mutans is a common cariogenic bacterium in the oral cavity involved in plaque formation. Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has been introduced into tooth mousse to encourage remineralization of dental enamel. The aim of this research was to study the effect of tooth mousse containing CPP-ACP (GC Tooth Mousse®) or CPP-ACP with 0.2% fluoride (CPP-ACPF; GC Tooth Mousse Plus®; GCP) on S. mutans planktonic growth and biofilm formation., Methods: S. mutans was cultivated in the presence of different dilutions of the tooth mousse containing CPP-ACP or CPP-ACPF, and the planktonic growth was determined by ATP viability assay and counting colony-forming units (CFUs). The resulting biofilms were examined by crystal violet staining, MTT metabolic assay, confocal laser scanning microscopy (CLSM), and scanning electron microscope (SEM)., Results: The CPP-ACP tooth mousse (GC) at a dilution of 5-50 mg/ml (0.5-5%) did not inhibit planktonic growth, and even increased the ATP content and the number of viable bacteria after a 24 h incubation. The same was observed for the CPP-ACPF tooth mousse (GCP), except for the higher concentrations (25 and 50 mg/ml) that led to a drop in the bacterial count. Importantly, both compounds significantly decreased S. mutans biofilm formation at dilutions as low as 1.5-3 mg/ml. 12.5 mg/ml GC and 6.25 mg/ml GCP inhibited biofilm formation by 90% after 4 h. After 24 h, the MBIC 90 was 6.25 mg/ml for both. CLSM images confirmed the strong inhibitory effect GC and GCP had on biofilm formation when using 5 mg/ml tooth mousse. SEM images of those bacteria that managed to form biofilm in the presence of 5 mg/ml tooth mousse, showed alterations in the bacterial morphology, where the streptococci appear 25-30% shorter on the average than the control bacteria., Conclusion: Our data show that the tooth mousse containing CPP-ACP reduces biofilm formation of the cariogenic bacterium S. mutans without killing the bacteria. The use of natural substances which inhibit biofilm development without killing the bacteria, has therapeutic benefits, especially in orthodontic pediatric patients.

Objective: To evaluate the effect of medical cannabis consumption on oral flora and saliva., Design: A clinical prospective study, at the rheumatology clinic of the Nazareth Hospital in Nazareth, recruiting consecutively patients approved for medical cannabis, evaluating their saliva flow, pH and microbial load of Streptococcus mutans and Lactobacillus, prior to and under medical cannabis treatment., Methods: Patients recently licensed for medical cannabis treatment, were recruited just prior to starting medical cannabis consumption (week 0), 1 and 4 weeks later, patients provided 5-minute time saliva samples, which were measured for their volume and pH, and cultured on a special microbial kit, evaluating the growth of Streptococcus mutans and Lactobacillus., Results: Out of 16 patients enrolled, 14 were female and had fibromyalgia. The mean age of the patients was 52.8±12.9 years. The mean saliva flow at week 0, week 1 and week 4 were 5.38±3.36 ml/5-minutes, 6 (p = 0.769) and 5.45 (p = 0.391), respectively, and for saliva pH were 6.28, 5.94 (p = 0.51) and 5.5 (p = 0.07) respectively also. The mean Streptococcus mutans growth score at weeks 0, 1 and 4 was1.8±0.75, 1.6±0.83 (p = 0.234), and 2.4±0.84 (p = 0.058), respectively. The mean Lactobacilli growth score at weeks 0, 1 and 4 was 2.59±0.88, 3.1±0.69 (p = 0.033) and 3.3±0.67 (p = 0.025), respectively., Conclusions: The results of this study show that medical cannabis consumption has no significant effect on saliva volume or pH, but it may be associated with changes in salivary levels of oral microbes such as Streptococcus mutans and Lactobacilli., Competing Interests: No competing interests.

Bacillus subtilis is a Gram-positive probiotic bacterium that successfully colonises plant roots due to its ability to utilise various sugars. The vast probiotic potential of B. subtilis has been recently demonstrated in numerous host organisms under different environmental conditions. We examined the probiotic potential of B. subtilis against the pathogenic bacterium Streptococcus mutans , which is involved in various oral disorders due to its robust biofilm-forming capability. B. subtilis cells attenuated biofilm formation by S. mutans during their dual growth in the presence of sugar alcohols. Transcription of genes encoding key enzymes in the metabolism of sugar alcohols by B. subtilis were highly induced. Moreover, growth-curve analysis suggested that B. subtilis is more efficient at early utilising sugar alcohols than S. mutans , as supported by the bacterial metabolic activity rates. Similarly, a comparison of secondary metabolites of mono and mixed cultures of B. subtilis and S. mutans indicated that B. subtilis is more active metabolically in the dual culture. Finally, knock-out mutations of the genes encoding key enzymes in the central metabolic pathway significantly reduced B. subtilis ' ability to mitigate biofilm formation by S. mutans . We conclude that effective metabolism of sugar alcohols by B. subtilis reinforces the probiotic potential of this bacterium against pathogenic species such as S. mutans .

The potential anti-cariogenic effect of blue light was evaluated using an oral biofilm model. Two species, Streptococcus mutans and Streptococcus sanguinis, were cultivated ex vivo on bovine enamel blocks for 24 h, either separately or mixed together, then exposed to blue light (wavelengths 400-500 nm) using 112 J/cm 2 . Twenty four or 48 h after exposure to light the biofilm structure and biomass were characterized and quantified using SEM and qPCR, respectively. Bacterial viability was analyzed by CLSM using live/dead bacterial staining. Gene expression was examined by RT-qPCR. After exposure to light, S. mutans biomass in mono-species biofilm was increased mainly by dead bacteria, relative to control. However, the bacterial biomass of S. mutans when grown in mixed biofilm and of S. sanguinis in mono-species biofilm was reduced after light exposure, with no significant change in viability when compared to control. Furthermore, when grown separately, an upregulation of gene expression related to biofilm formation of S. mutans, and downregulation of similar genes of S. sanguinis, were measured 24 h after exposure to blue light. However, in mixed biofilm, a downregulation of those genes in both species was observed, although not significant in S. mutans. In conclusion, blue light seems to effectively alter the bacterial biomass by reducing the viability and virulence characteristics in both bacterial species and may promote the anti-cariogenic balance between them, when grown in a mixed biofilm. Therefore, exposure of oral biofilm to blue light has the potential to serve as a complementary approach in preventive dentistry.

Endocannabinoid/endocannabinoid-like (EC/EC-like) are natural endogenous compounds which have been found to affect MRSA pathogenicity. Our previous studies showed that EC/EC-like was able to impair staphylococcal biofilm formation and maintenance as well as to alter biofilm-associated virulence factors. In the present study, we investigated the combinatory effect of the selected EC/EC-like with a natural antimicrobial agent, poly-L-lysine, on cariogenic bacteria Streptococcus mutans growth and biofilm formation. Among four tested EC/EC-like, only two, anandamide (AEA) and oleoylethanolamide (OEA), exhibited synergistic combinatory effect with poly-L-lysine against S . mutans . We attribute this distinct effect to differences in the fatty acid chain structure of the selected EC/EC-like compounds. Moreover, AEA exerted a specific antibiofilm mode of action against S . mutans by effecting total inhibition of biofilm formation while still allowing bacteria viability. Finally, we postulate that the presence of EC/EC-like and poly-L-lysine could enhance the permeability and efficacy of each other via hydrophobic and electrostatic interactions with the S . mutans membrane. In conclusion, we assume that a combination of endogenous natural compounds such as EC/EC-like and poly-L-lysine may benefit oral hygiene by preventing dental plaque., Competing Interests: The authors declare that they have no conflicts of interest regarding the publication of this paper., (Copyright © 2020 Mark Feldman et al.)

Thiazolidinediones (TZDs) have been found to act as effective quorum sensing quenchers, capable of preventing biofilm formation. Our previous studies demonstrated a profound antibiofilm effect of the TZD derivative thiazolidinedione-8 (S-8), either in solution or incorporated into a sustained-release membrane (SRM-S-8) under batch conditions. In the present study, we used a constant depth film fermenter model in order to investigate the impact of SRM-S-8 on mixed C. albicans - S. mutans biofilm development, under flow conditions. We found that essential parameters of cospecies biofilm maintenance and maturation, such as metabolic activity, biofilm thickness, roughness, extracellular polysaccharides production, and morphology of both pathogens, were altered by SRM-S-8 in the flow system. We propose that prolonged and sustained release of S-8 in a flow-through system allows better penetration of the active agent to deeper layers of the mixed biofilm, thereby increasing its activity against both pathogens. In conclusion, the use of a locally applied sustained-release drug delivery system of S-8 can affect the dental polymicrobial biofilm, resulting in clinical improvements and a better patient compliance.

In prior studies, exposure of Streptococcus mutans in biofilm to blue light using high fluences of up to 680 J/cm(2) did not interfere with bacterial capability to reform an initial biofilm; however, a delayed antibacterial effect was observed. Our aim was to determine the sustained effecttts of blue light-emitting diode (LED) curing light on the pathogenicity of the newly formed biofilm. S. mutans were grown to form biofilm that was exposed to blue light (wavelengths, 460-480 nm) for 1, 3, and 7 min (equivalent to 37, 112, and 262 J/cm(2), respectively). Then, bacteria were suspended and allowed to regrow into new biofilms. The regrown biofilms were assessed for bacterial quantification by optical density (OD) measurement and quantitative polymerase chain reaction (qPCR), bacterial viability and extracellular polysaccharide production by fluorescent staining using confocal scanning laser microscopy, acid production by bacteria (acidogenicity), and bacterial survival at low pH (aciduricity) using qPCR. Bacterial growth in the regrown biofilms was increased when samples were previously exposed to light; however, under the confocal microscopy, a higher proportion of dead bacteria and a reduction in polysaccharide production were observed. The acidogenicity from the regrown biofilm was lowered as fluences of light increased. The aciduricity of the regrown biofilm was decreased, meaning less growth of bacteria into biofilm in low pH with increasing fluences. Blue light has sustained effects on S. mutans bacteria grown into new biofilm. Although bacterial growth in biofilm increased, bacterial viability and virulence characteristics were impaired. The cariogenic potential over time of S. mutans previously exposed to blue light when grown on tooth surfaces is yet to be determined.

Background and Objectives: CO2 laser irradiation of tooth enamel can inhibit demineralization of tooth enamel, by changing enamel composition and resistance to acid attack. The aim of this work was to examine these effects of CO2 laser irradiation on enamel covered by biofilm., Materials and Methods: Streptococcus mutans was grown on bovine enamel surfaces for 48 hours to form a mature biofilm. Samples were irradiated by CO2 laser (wavelength of 10.6 µm) at a power of 0.08 W in a super-pulse mode for 1 second and 24 pulses/second, with an energy density of 0.77 J/cm(2) per pulse. Untreated controls and laser treated samples with and without biofilm were examined for the morphology of the biofilm and the enamel surface by scanning electron microscopy (SEM). Structural biofilm viability was assessed using confocal laser scanning microscopy with live/dead staining. The biofilm was removed in a sonication water bath and the non-treated and irradiated enamel samples were chemically analyzed using energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR)., Results: Irradiated samples showed a melt zone with micro-cracks in the center of the irradiating beam position, which was smaller when irradiated enamel was covered by biofilm. Confocal microscopy images demonstrated higher proportion of dead bacteria at the margins of the irradiated spot area, while at the spot center the bacteria were evaporated exposing the enamel surface to direct laser irradiation. EDS analysis showed an increase in Ca/P ratio after irradiation of enamel covered with biofilm. FTIR analysis showed an approximately 40% carbonate loss in the irradiated enamel samples, including those with biofilms., Conclusion: Biofilms protect enamel surfaces from possible morphological irradiation damage without interfering with the resultant chemical changes that may increase the enamel resistance to acid attack. Therefore, under certain exposure regimens that are thermally and mechanically safe for enamel, CO2 laser irradiation of biofilms on dental hard tissues is suggested as a potential novel preventive treatment for controlling dental caries., (© 2014 Wiley Periodicals, Inc.)

Unlabelled: Abstract Objective: The aim of this work was to study the effect of CO2 laser light on gene expression of Streptococcus mutans in a planktonic environment irradiated by sublethal energies., Background Data: The use of the CO2 laser for oral clinical applications has great benefits over the traditional procedures, including a reduced bacterial environment., Materials and Methods: In order to determine the sublethal irradiation dose, S. mutans in suspension was irradiated with a continuous wave CO2 laser (wavelength 10.6 μm) for duration times of 0.5-1.5 min at fluences ranging from 65 to 536 J/cm(2), following bacterial growth and viability measurements. The effect of CO2 laser irradiation at sublethal dose on gene expression was evaluated by DNA microarray. Temperature rise in the suspension caused by laser irradiation was measured using thermocouple electrodes., Results: Bacterial growth and viability began to decrease after exposure to laser irradiation using 284 J/cm(2). Following irradiation with sublethal fluences of 134 and 268 J/cm(2), changes in gene expression were found with seven downregulated genes being common to both fluences. The temperature rise in the bacterial sample after irradiation with 268 J/cm(2) was from room temperature to only 35°C., Conclusions: CO2 laser irradiation inhibited viability and growth of S. mutans in suspension in a dose-dependent manner. Irradiation of planktonic bacterial suspensions with sublethal fluences resulted in changes mostly of downregulation in gene expression in a fashion similar to S. mutans in biofilm, except that different genes were involved.

Our aim was to examine the viability and structure of new biofilm formed by Streptococcus mutans that was previously exposed to blue light. S. mutans bacteria were grown to form a mature biofilm, that was exposed to blue light (wavelengths, 400-500 nm) for 1-10 min (equivalent to 68-680 J/cm(2)). Biofilm was dispersed by sonication, and then the suspended bacteria were grown to re-organize as a new biofilm. Biofilm formation after 2, 4, and 6 h, was examined by viable counts and by confocal laser scanning microscopy using live/dead bacterial staining. A significant decrease in bacterial viability was found in the 6h biofilms formed by bacteria that had been previously exposed to blue light for 7 or 10 min. Confocal microscopy images showed a decrease in the live/dead bacterial ratio after 3-10 min of light exposures. Dead bacteria were mainly at the outer layers of the biofilm. Exposure of S. mutans in biofilm to blue light affected the re-formation of a new biofilm, showing an increase in the amount of dead bacteria. This phenomenon suggests that blue light has a delayed antibacterial effect, although it does not interfere with bacterial capability to reform an initial biofilm., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Garlic has been used medicinally throughout human history. Allicin is considered the most therapeutic constituent of garlic. This study tested the antimicrobial activity of garlic allicin on oral pathogens associated with dental caries and periodontitis. Allicin was found effective against all the tested bacteria. The broth dilution method revealed that planktonic growth of the cariogenic, gram-positive species Streptococcus mutans, S. sobrinus, and Actinomyces oris was inhibited by an allicin concentration of 600 μg/mL or higher. Planktonic growth of the tested gram-negative periopathogenic species Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum was inhibited by a minimum allicin concentration of 300 μg/mL. Porphyromonas gingivalis, an anaerobic, gram-negative pathogen and the bacterium most associated with chronic periodontitis, demonstrated the lowest sensitivity to allicin (2,400 μg/mL). Gel zymography and the synthetic chromogenic substrate N(α)-benzoyl-L-arginine 4-nitroanilide hydrochloride demonstrated that allicin inhibits the proteases of P. gingivalis, including the arginine and lysine gingipains known as major virulence factors of this organism. A gingipain-inactivated mutant demonstrated high sensitivity to allicin (<300 μg/mL), revealing that gingipains confer resistance to allicin. Live/dead staining followed by analysis with confocal laser scanning microscopy revealed that allicin was bactericidal to S. mutans grown in mature biofilms. However, this bactericidal effect was reduced as biofilm depth increased. In conclusion, these results support the traditional medicinal use of garlic and suggest the use of allicin for alleviating dental diseases.

Purposes: (1) To determine the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and acidulated phosphate fluoride (APF) on S. mutans viability, (2) to observe their effects on biofilm structure, and (3) to examine the element content of the hydroxyapatite (HA) surfaces after exposure to CPP-ACP and APF., Methods: HA discs were coated with: CPP-ACP (GC Tooth-Mousse), APF, CPP-ACP+APF (1/1). Uncoated HA discs were used as control. Following application of the materials, the discs were immersed in human saliva and incubated with S. mutans ATCC (27315) for 24 hours. Growth of bacteria on the discs was evaluated by microbial culturing methods. The structure of the biofilm was examined with confocal laser scanning microscope (CLSM). The change in element content of HA surfaces (without biofilm) was evaluated with energy-dispersive x-ray spectroscopy (EDS). The values were statistically analyzed using Kruskal-Wallis and Dunn's test., Results: The total number of bacteria of APF and CPP-ACP+APF applied groups were found significantly lower than the control group (P< 0.05). All specimens showed similar microbial colonization structure. No statistically significant differences were observed in O, F, Na, P, Ca content on HA surfaces after exposure to the tested agents, although fluoride concentration of the APF treated HA surfaces were increased compared to CPP-ACP, CPP-ACP +APF.

Streptococcus mutans colonizing on tooth surfaces is one of the major causative agents of human dental caries. Despite numerous studies conducted on lasers and oral tissue interactions, little is known about the effect of laser energy on S. mutans gene expression in a biofilm form. The aim of this study was to investigate the effect of sublethal energies of CO(2) laser on biofilm and gene expression of the oral bacteria S. mutans immobilized in biofilm. S. mutans biofilm was irradiated with CO(2) laser. Vitality and construction of the biofilm were observed by confocal laser scanning microscopy and scanning electron microscopy. The effect of laser irradiation on gene expression was evaluated by DNA microarray. CO(2) laser irradiation had a dose effect on the viability of S. mutans immobilized in biofilm. A nonsignificant lethal effect was observed at 31 J/cm(2) while at higher energy of 70 and 144 J/cm(2) an antibacterial effect was recorded. The mode of antibacterial action seems to be from the inner layers toward the outer layer of the biofilm, indicating the influence of the surface on the killing effect. At 31 J/cm(2), microarray analysis indicated a moderate effect on S. mutans gene expression due to CO(2) laser irradiation, mainly down-regulating genes related to bacterial stress response. In conclusion, laser irradiation at sublethal energy had an effect on gene expression of S. mutans., (Copyright © 2011 S. Karger AG, Basel.)

Background: Adhesion and successful colonization of bacteria onto solid surfaces play a key role in biofilm formation. The initial adhesion and the colonization of bacteria may differ between the various types of surfaces found in oral cavity. Therefore, it is conceivable that diverse biofilms are developed on those various surfaces. The aim of the study was to investigate the molecular modifications occurring during in vitro biofilm development of Streptococcus mutans UA159 on several different dental surfaces., Results: Growth analysis of the immobilized bacterial populations generated on the different surfaces shows that the bacteria constructed a more confluent and thick biofilms on a hydroxyapatite surface compared to the other tested surfaces. Using DNA-microarray technology we identified the differentially expressed genes of S. mutans, reflecting the physiological state of biofilms formed on the different biomaterials tested. Eight selected genes were further analyzed by real time RT-PCR. To further determine the impact of the tested material surfaces on the physiology of the bacteria, we tested the secretion of AI-2 signal by S. mutans embedded on those biofilms. Comparative transcriptome analyses indicated on changes in the S. mutans genome in biofilms formed onto different types of surfaces and enabled us to identify genes most differentially expressed on those surfaces. In addition, the levels of autoinducer-2 in biofilms from the various tested surfaces were different., Conclusions: Our results demonstrate that gene expression of S. mutans differs in biofilms formed on tested surfaces, which manifest the physiological state of bacteria influenced by the type of surface material they accumulate onto. Moreover, the stressful circumstances of adjustment to the surface may persist in the bacteria enhancing intercellular signaling and surface dependent biofilm formation.

Context: Cranberry juice has long been recognized in folk medicine as a therapeutic agent, mainly in urinary tract infections. Its proposed mechanism of action is antiadhesion of bacteria., Objective: Investigation of the potential antiadhesion effect of nondialyzed material of cranberry (NDM) via its influence on secretion, gene expression, and promoter activity of the fructosyltransferase (FTF), which is among the extracellular enzymes associated with dental biofilm formation and pathogenesis of oral bacteria., Main Outcome Measures: Secretion of FTF from Streptococcus mutans, in the presence of NDM, was measured by immunoblotting and confocal scanning laser microscopy. Its influence on ftf gene expression was determined by reverse transcription followed by real-time RT-PCR. The luciferase assay was used to detect bioluminescence expressed by the ftf promoter activity of bacteria exposed to NDM., Results: NDM at concentrations between 0.2/mL and 1mg/mL significantly (P<.05) decreased secretion of extracellular FTF, as well as down-regulated ftf expression in a dose-dependent manner. NDM also markedly reduced the luciferase activity under the ftf promoter.

Background: A biofilm is a complex community of microorganisms that develop on surfaces in diverse environments. The thickness of the biofilm plays a crucial role in the physiology of the immobilized bacteria. The most cariogenic bacteria, mutans streptococci, are common inhabitants of a dental biofilm community. In this study, DNA-microarray analysis was used to identify differentially expressed genes associated with the thickness of S. mutans biofilms., Results: Comparative transcriptome analyses indicated that expression of 29 genes was differentially altered in 400- vs. 100-microns depth and 39 genes in 200- vs. 100-microns biofilms. Only 10 S. mutans genes showed differential expression in both 400- vs. 100-microns and 200- vs. 100-microns biofilms. All of these genes were upregulated. As sucrose is a predominant factor in oral biofilm development, its influence was evaluated on selected genes expression in the various depths of biofilms. The presence of sucrose did not noticeably change the regulation of these genes in 400- vs. 100-microns and/or 200- vs. 100-microns biofilms tested by real-time RT-PCR. Furthermore, we analyzed the expression profile of selected biofilm thickness associated genes in the luxS- mutant strain. The expression of those genes was not radically changed in the mutant strain compared to wild-type bacteria in planktonic condition. Only slight downregulation was recorded in SMU.2146c, SMU.574, SMU.609, and SMU.987 genes expression in luxS- bacteria in biofilm vs. planktonic environments., Conclusion: These findings reveal genes associated with the thickness of biofilms of S. mutans. Expression of these genes is apparently not regulated directly by luxS and is not necessarily influenced by the presence of sucrose in the growth media.

Aim: To assess whether parental involvement can improve children's oral health as a strategiy to reduce caries risk in children undergoing orthodontic treatment., Methods: The study population consisted of 40 healthy children aged 7 to 15 years (mean 10.93 ± 2.78) and their accompanying parents (mother or father). Oral hygiene instructions were given simultaneously to all children and accompanying parents every 6 weeks at their regular orthodontic appointments. Levels of Streptococcus mutans and salivary buffer capacity were assessed for both children and parents before and 9 months into orthodontic treatment., Results: The majority of children (74%) and parents (92%) expressed unchanged levels of Streptococcus mutans and stable salivary buffer capacity throughout the study. When analyzing child-parent pairs with respect to Streptococcus mutans and salivary buffer capacity, no significant differences were found prior to treatment. Nine months into treatment, 57% of the children and parents still showed similar Streptococcus mutans counts and buffer capacity., Conclusion: The child-parent approach succeeded in preventing deterioration of children's oral hygiene. Parental involvement has an essential part in maintaining children's oral health. Oral health care professionals should partner with parents when implementing any kind of health behavior., (COPYRIGHT © 2008 BY QUINTESSENCE PUBLISHING CO, INC.)

Oral biofilms are associated with the most common infections of the oral cavity. Bacteria embedded in the biofilms are less sensitive to antibacterial agents than planktonic bacteria are. Recently, an antibacterial synergic effect of noncoherent blue light and hydrogen peroxide (H(2)O(2)) on planktonic Streptococcus mutans was demonstrated. In this study, we tested the effect of a combination of light and H(2)O(2) on the vitality and gene expression of S. mutans embedded in biofilm. Biofilms of S. mutans were exposed to visible light (wavelengths, 400 to 500 nm) for 30 or 60 s (equivalent to 34 or 68 J/cm(2)) in the presence of 3 to 300 mM H(2)O(2). The antibacterial effect was assessed by microbial counts of each treated sample compared with that of the control. The effect of light combined with H(2)O(2) on the different layers of the biofilm was evaluated by confocal laser scanning microscopy. Gene expression was determined by real-time reverse transcription-PCR. Our results show that noncoherent light, in combination with H(2)O(2), has a synergistic antibacterial effect through all of the layers of the biofilm. Furthermore, this treatment was more effective against bacteria in biofilm than against planktonic bacteria. The combined light and H(2)O(2) treatment up-regulated the expression of several genes such as gtfB, brp, smu630, and comDE but did not affect relA and ftf. The ability of noncoherent visible light in combination with H(2)O(2) to affect bacteria in deep layers of the biofilm suggests that this treatment may be applied in biofilm-related diseases as a minimally invasive antibacterial procedure.

Streptococcus mutans is known as a primary pathogen of dental caries, one of the most common human infectious diseases. Exopolysaccharide synthesis, adherence to tooth surface and biofilm formation are important physiological and virulence factors of S. mutans. In vitro comparative gene expression analysis was carried out to differentiate 10 selected genes known to be mostly involved in S. mutans biofilm formation by comparing the expression under biofilm and planktonic environments. Real-time RT-PCR analyses indicated that all of the genes tested were upregulated in the biofilm compared to cells grown in planktonic conditions. The influence of simple dietary carbohydrates on gene expression in S. mutans biofilm was tested also. Among the tested genes, in the biofilm phase, the greatest induction was observed for gtf and ftf, which are genes encoding the extracellular polysaccharide-producing enzymes. Biofilm formation was accompanied by a 22-fold induction in the abundance of mRNA encoding glucosyltransferase B (GTFB) and a 14.8 -fold increase in mRNA encoding GTFC. Levels of mRNA encoding fructosyltransferase were induced approximately 11.8-fold in biofilm-derived cells. Another notable finding of this study suggests that glucose affects the expression of S. mutans GS5 biofilm genes. In spite of a significant upregulation in biofilm-associated gene expression in the presence of sucrose, the presence of glucose with sucrose reduced expression of most tested genes. Differential analysis of the transcripts from S. mutans, grown in media with various nutrient contents, revealed significant shifts in the expression of the genes involved in biofilm formation. The results presented here provide new insights at the molecular level regarding gene expression in this bacterium when grown under biofilm conditions, allowing a better understanding of the mechanism of biofilm formation by S. mutans.

Streptococcus mutans often adopts a sessile biofilm lifestyle that differs greatly from that of free-living cells. Biofilm formation represents a protected mode of growth that allows cells to survive in hostile environments. In this study, in vitro comparative transcriptome analysis was carried out to identify genes that are differentially expressed in biofilm of S. mutans compared with free-living cells. DNA-microarray analyses indicated that about 12 % of genes showed significant differential expression: 139 were activated and 104 were repressed in biofilm vs the planktonic environment. The differential expression of 20 selected genes was confirmed by real-time RT-PCR. In addition, regulation of expression of these genes during biofilm development was tested in 100 and 400 microm deep biofilms. Direct comparison of optical images consistently demonstrated that changes in biofilm thickness are accompanied by significant shifts in cell viability. From evaluation of gene expression patterns, it was shown that the majority of the genes tested were significantly down-regulated in 400 vs 100 microm deep biofilms. This study provides a genome-scale synopsis and adds important insights into gene expression in biofilm development processes of S. mutans, which are strongly associated with the pathogenesis of dental diseases.

Dental caries is one of the most common infectious diseases that affects humans. Streptococcus mutans, the main pathogenic bacterium associated with dental caries, produces a number of extracellular sucrose-metabolizing enzymes, such as glucosyltransferases (GTFB, GTFC and GTFD) and fructosyltransferase (FTF). The cooperative action of these enzymes is essential for sucrose-dependent cellular adhesion and biofilm formation. A global response regulator (vicR) plays important roles in S. mutans ftf and gtf expression in response to a variety of stimuli. A real-time reverse-transcription polymerase chain-reaction was used to quantify the relative levels of ftf, gtfB, gtfC, gtfD and vicR transcription of S. mutans in the presence of various dietary carbohydrates: sucrose, D-glucose, D-fructose, D-glucitol (D-sorbitol), D-mannitol and xylitol. Ftf was highly expressed at late exponential phase in the presence of sorbitol and mannitol. GtfB was highly expressed in the presence of all the above carbohydrates except for xylitol at early exponential growth phase and glucose and fructose at late exponential growth phase. Similar to gtfB, the expression of gtfC was also induced with the presence of all the tested carbohydrates except for xylitol at early growth and glucose and fructose at late exponential phase. In addition, no effect of mannitol on gtfC expression at early exponential phase was observed. GtfD was less influenced compared to the gtfB and gtfC, demonstrating enhanced expression especially in the presence of sorbitol, glucose, mannitol and xylitol at early exponential phase and mannitol at late exponential phase. VicR expression was induced only at the presence of xylitol at late exponential phase, and a decrease in expression was recorded at early exponential phase. Our findings show that dietary carbohydrates have a major influence on the transcription of ftf, gtfB, gtfC and gtfD, but less on vicR. Sorbitol and mannitol, which are considered as noncariogenic sugar substitutes, may indirectly affect caries by promoting biofilm formation via enhanced expression of gtfs and ftf. These results suggest regulatory circuits for exopolysaccharide gene expression in S. mutans.

Objectives: The glucosyltransferase (GTF) and fructosyltransferase (FTF) enzymes play a pivotal role in dental biofilm formation as they synthesize polysaccharides that act as the extracellular matrix of the biofilm. Iodine is a unique antibacterial agent that has distinct properties from other conventional antibacterial agents. In this study we have examined the effect of iodine and povidone iodine (PI) on gtf and ftf expression in biofilm and planktonic environments and on immobilized and unbound GTF and FTF activity., Methods: Real-time reverse transcription-PCR was used to investigate the effect of iodine and PI on ftf, gtfB and gtfC expression. The effect of iodine and PI on GTF and FTF activity was tested using radioactive assays., Results: Our results indicate that iodine and PI in a tetraglycol carrier cause enhancement of expression of gtfB in Streptococcus mutans in biofilms but not in planktonic bacteria. PI in water induced expression of gtfB and gtfC in planktonic bacteria. However, iodine and PI strongly inhibit polysaccharide production by GTF and to a lesser extent by FTF activity. The inhibitory effect on GTF activity was similar in solution compared to its activity in the immobilized environment. This unique effect may be attributed to the distinct chemical properties of iodine compared with other antibacterial agents., Conclusions: This study indicates that iodine at sub-bactericidal concentrations demonstrates molecular and enzymatic effects that are highly associated with biofilm formation.

Dental diseases are chronic infections caused by oral bacteria harboring the dental biofilm. Local sustained-release delivery systems prolong the duration of a drug in the oral cavity, thus enhancing its therapeutic potential, while reducing its side effects. Triclosan is an agent that was found to have an antibacterial effect against oral bacteria. However, its substantivity in the oral cavity is low, resulting in reduced antibacterial efficiency. The purpose of this study was to develop a local sustained release device containing triclosan and to test its antibacterial efficacy on Streptococcus mutans biofilm. Our results show that we can formulate an ethylcellulose-based, nondegradable, sustained-release device in which 80% of the loaded triclosan is released over a 10-day period. The release rate of triclosan corresponded to the Higuchi's planar homogenous diffusion release model (r2 = 0.998). A degradable local sustained-release delivery based on a methacrylate ester matrix was also developed for a faster release rate of triclosan. The release kinetics in those types of sustained-release delivery systems was erosion control. The local sustained-release delivery system significantly affected the viability of S. mutans in biofilm compared to placebo as was tested by confocal laser scanning microscopy. Our in vitro results show that triclosan can be incorporated into degradable or nondegradable sustained-release drug delivery systems. The release of triclosan from the local sustained-release delivery system can be controlled, thus extending its antibacterial properties., ((c) 2005 Wiley Periodicals, Inc.)

Objectives: To evaluate the possibility of enhancing the phototoxic effect on Streptococcus mutans using a potentially antibacterial synergic effect between blue light and hydrogen peroxide (H2O2), and to investigate the antibacterial mechanism involved., Methods: Growth of S. mutans samples was determined after exposure to light in the presence and absence of H2O2. The effect of such light on H2O2 degradation, on reactive oxygen species (ROS) generation and on the exposed-medium temperature was examined., Results: The combination of light exposure for 20 s (approximately 23 J/cm2) and a concentration of 0.3 mM H2O2 yielded 96% growth inhibition, whereas, when applied separately, light exposure decreased bacterial growth by 3% and H2O2 by 30% compared with the control. The results showed no direct effect of the light on H2O2 degradation, a partial protective effect of ROS scavengers on S. mutans and a non-lethal increase in the medium temperature after light exposure., Conclusions: An antibacterial synergic effect between blue light and H2O2 was observed. The mechanism of the phototoxic effect on S. mutans was basically a photochemical process, in which ROS were involved. Application of such light in combination with H2O2 to an infected tooth could be an alternative to or serve as an additional minimally invasive antibacterial treatment.

Dental diseases are among the most prevalent afflictions of humankind. These diseases are associated with the formation of biofilms harbouring pathogenic bacteria. Eight different derivatives of oxazaborolidines were synthesised and evaluated for their affect on Streptococcus mutans adhesion and biofilm formation. Structure-activity relationship was observed. The B-butyl moiety of the oxazaborolidines contributed an anti-adhesion effect for all derivatives, whilst its effect diminished when the boron atom was incorporated in a fused heterocyclic ring. The B-phenyl group induced bacterial adhesion in all tested compounds Oxazaborolidines may serve as novel agents for affecting oral biofilm formation. Moreover, the ability to alter the oxazaborolidine molecule and thus affect biofilms offers an excellent opportunity to study biofilm formation.

Streptococcus mutans produces a fructosyltransferase (FTF) enzyme, which synthesizes fructan polymers from sucrose. Fructans contribute to the virulence of the biofilm by acting as binding sites for S. mutans adhesion and as extracellular nutrition reservoir for the oral bacteria. Antibodies raised against a recombinant S. mutans FTF were used to test the effect of glucose, fructose, and sucrose on FTF expression in S. mutans GS-5 biofilms. Biofilms formed in the presence of fructose and glucose showed a higher ratio of FTF compared to biofilms formed in the presence of sucrose. Confocal laser scanning microscopy images of S. mutans biofilms indicated a carbohydrate-dependent FTF distribution. The layer adjacent to the surface and those at the liquid interface displayed high amounts cell-free FTF with limited amount of bacteria while the in-between layers demonstrated both cell-free FTF and cells expressing cell-surface FTF. Biofilm of S. mutans grown on hydroxyapatite surfaces expressed several FTF bands with molecular masses of 160, 125, 120, 100, and 50 kDa, as detected by using FTF specific antibodies. The results show that FTF expression and distribution in S. mutans GS-5 biofilms is carbohydrate regulated.

Background: Previous studies have shown that high molecular-weight non-dialysable material derived from cranberry juice (NDM) inhibits co-aggregation of a variety of oral bacteria., Objectives: In the present study, we examined the effect of NDM on several constituents of the dental biofilm, glucosyltransferase (GTF) and fructosyltransferase (FTF), as well as on the adhesion of Streptococcus sobrinus., Results: The activity of immobilized and soluble GTF and FTF was inhibited by NDM (P > 0.05). NDM also inhibited adhesion of S. sobrinus to hydroxyapatite (P < 0.05)., Conclusions: Our results indicate that NDM may affect biofilm formation. One of the proposed mechanisms is via inhibition of extracellular polysaccharide synthesis, which promote the sucrose-dependent adhesion of oral bacteria as S. sobrinus.

Several representative oxazaborolidines have been synthesized and evaluated against S. mutans for antibacterial activity. This is the first reported antibacterial activity of this class of compounds. The minimal inhibitory concentration values ranged from 0.53 to 6.75 mM.

Streptococcus mutans utilizes sucrose to synthesize glucans by glucosyltransferase and fructans by fructosyltransferase (FTF). Antibodies raised against a recombinant FTF were used to study S. mutans FTF secretion. Low amounts of cell-free FTF were found in culture of S. mutans grown with sucrose, while an increase in bacteria displaying cell surface FTF was detected. FTF added to S. mutans cultures was adsorbed to bacteria grown with sucrose but not to bacteria grown with glucose or fructose or to a gtf inactivated mutant grown with sucrose. Recombinant FTF was found to have high affinity for glucans suggesting that fructans and glucans are an integral part of the polysaccharide matrix of oral biofilms.

Previous investigations showed that a high molecular mass, non-dialyzable material (NDM) from cranberries inhibits the adhesion of a number of bacterial species and prevents the co-aggregation of many oral bacterial pairs. In the present study we determined the effect of mouthwash supplemented with NDM on oral hygiene. Following 6 weeks of daily usage of cranberry-containing mouthwash by an experimental group (n = 29), we found that salivary mutans streptococci count as well as the total bacterial count were reduced significantly (ANOVA, P < 0.01) compared with those of the control (n = 30) using placebo mouthwash. No change in the plaque and gingival indices was observed. In vitro, the cranberry constituent inhibited the adhesion of Streptococcus sobrinus to saliva-coated hydroxyapatite. The data suggest that the ability to reduce mutans streptococci counts in vivo is due to the anti-adhesion activity of the cranberry constituent.

Purpose: The purpose of the study was to assess mutans streptococci (MS) count in children who were treated for early childhood caries (ECC) in a follow-up examination., Methods: Forty-four children who were treated for ECC in the pediatric dentistry clinic of the Hebrew University-Hadassah School of Dental Medicine were given paraffin film to chew. A blade containing children's saliva was placed inside a test tube containing MS selective medium to allow bacteria growth. The kits were transferred immediately to the laboratory and incubated for 48 hours in a 37 degrees C incubator. After incubation, bacterial growth was counted by the amount of colonies formed., Results: Children who were examined closer to the end of the dental treatment demonstrated significantly lower MS counts. In addition, children who had higher birth weight also demonstrated lower bacterial counts. Significantly more parents of children with the high MS group than in the low MS group count reported that oral hygiene instructions greatly reduced children's plaque levels. All the children who were born preterm had high MS count, while 77% of children who were born at term demonstrated high MS count., Conclusions: Children who had dental treatment due to ECC may have high MS count in the future and are at risk for caries attack. Factors that may be associated with high MS counts are low birth weight and mother's education.

This study evaluated the effect of sustained-release chlorhexidine varnish on orthodontic patients. Ten children, ages 10 to 16 years, participated. Bacterial levels of Streptococcus mutans and Actinomyces viscosus and total counts were evaluated in sputum samples. These counts were evaluated at 4 stages: before orthodontic treatment, at least 2 weeks after bonding of the brackets, 1 week after application of chlorhexidine varnish, and 3 weeks after application of chlorhexidine varnish. Increases in bacterial levels of S mutans and in the total bacterial count were detected after the brackets were bonded. One week after the sustained-release chlorhexidine varnish was applied, a significant decrease of total bacterial levels and S mutans was observed. This decrease persisted for 3 weeks after the first application. No significant change in A viscosus levels occurred during that period. The results provide additional evidence that sustained-release chlorhexidine varnish decreases S mutans levels in orthodontic patients with fixed appliances and therefore might be useful in preventing caries lesions.

Purpose: To examine the effect of toothbrushing with different brands of regular (Meridol, Colgate) and whitening toothpaste (Pearl Weiss, Rembrant, Email Diamant) on bacterial adhesion onto enamel surfaces in vitro., Materials and Methods: Extracted intact human teeth were brushed twice a day, for 3 minutes with the tested toothpaste for a period of 7 days. Sucrose dependent adhesion of Streptococcus mutans to the tested teeth was measured using pre-radioactive labeled bacteria., Results: S. mutans adhered more to enamel surfaces, pre-brushed with the tested toothpastes, than to teeth which were not brushed. Different profiles of bacterial adhesion were recorded. Both Diamant and Rembrant toothpastes increased bacterial affinity toward the enamel surface as compared to the other toothpastes. Meridol and Pearl Weiss demonstrated a similar adhesion effect as the etching control while brushing with Colgate demonstrated the least bacterial adhesion.

This study describes properties of potential sustained release varnishes (SRV) containing amine fluoride or amine fluoride with stannous fluoride. The release kinetics, antibacterial properties and antiadhesion properties of two potential varnishes were tested. The varnish of ethylcellulose matrix was found to release fluoride for 4 h in vitro, while the formulation based on hydroxypropylmethylcellulose acetate succinate had a rapid release rate. Hydroxyapatite tablets coated with ethylcellulose-based SRV increased adhesion of Streptococcus mutans, while tablets coated with hydroxypropylmethylcellulose acetate succinate-based SRV decreased bacterial adhesion. Both types of SRV demonstrated a strong antibacterial effect on bacteria in biofilm., (Copyright 2002 S. Karger AG, Basel)

Aims: To investigate the formation of fructosyltransferase (FTF) complexes on hydroxyapatite (HA) surfaces., Methods and Results: Cell-free extracellular FTF from Streptococcus mutans, purified from hyperproducing strain V-1995, was adsorbed onto HA and then eluted from the surface by means of a concentration gradient of potassium phosphate buffer. The FTF monomers loaded onto HA formed, upon adsorption, various complexes ranging from 200 to 700 kDa as demonstrated using native PAGE. All these complexes exhibited enzymatic activity., Conclusions: Adsorption of FTF onto HA induced the formation of stable and enzymatically-active complexes., Significance and Impact of the Study: The formation of these complexes may explain the change of FTF catalytic properties after adsorption onto HA. This study is another step in determining the properties of a-cellular constituents of the oral biofilm.

Bacteria in biofilm and planktonic bacteria exhibit different properties. The objective of the present study was to compare the growth rates of Streptococcus sobrinus and Streptococcus mutans on different types of biofilm with their planktonic growth rate. Our experimental model consisted of hydroxyapatite beads coated with human saliva (sHA). Glucans or fructans were synthesized in situ on sHA by immobilized cell-free glucosyltransferase or fructosyltransferase isolated from oral bacteria. S. sobrinus or S. mutans was then adsorbed onto the glucan- or fructan-coated sHA and incubated for different time intervals. The depth of the developing biofilm was measured. Our results show that growth rates of S. sobrinus and S. mutans on both fructan- and glucan-coated sHA were similar during a 23 h period. In addition, the profile was similar to the growth profile of the same planktonic bacteria. The resemblance in growth rates between planktonic and biofilm bacteria may be attributed to the thin and non-dense biofilm formed in the initial stages of the biofilm formation. The thin biofilm coat, reaching a maximal depth of 11 microm, has only imposed limited diffusion restrictions, thus not affecting the growth of the bacteria in the biofilm. Our study shows that growth of bacteria on surfaces may resemble their growth in suspension if the bacteria are not embedded in a thick dense biofilm.

Extracellular polysaccharides (PS) synthesized by oral bacteria constitute one of their major virulence factors. The PS, synthesized from sucrose, facilitate adhesion and colonization by bacteria to tooth surfaces. The study was designed to test the effect of in situ production of extracellular PS by Streptococcus mutans on the bactericidal activity of human neutrophils. These effects were tested on bacteria pre-exposed to sucrose (PS-positive Strep. mutans) and compared to bacteria not exposed to sucrose (PS-negative Strep. mutans). The interactions between neutrophils and Strep. mutans were tested in suspension and on bacteria in an experimental model of dental plaque. Viability of Strep. mutans was measured by [3H]-thymidine incorporation into the bacteria. Degranulation of neutrophils was evaluated by the release of lysozyme, and the production of reactive oxygen products was measured by chemiluminescence. When neutrophils were incubated with suspended bacteria, the viability of PS-negative Strep. mutans was 20% of that of bacteria not incubated with neutrophils (control), while the viability of PS-positive Strep. mutans was 40% of the control. In the experimental dental-plaque model, 50% of the PS-negative Strep. mutans were killed by neutrophils while the viability of PS-positive Strep. mutans was not different than of the control. Degranulation of neutrophils was not affected by the presence of extracellular PS of Strep. mutans. Artificial stimulation of neutrophils with phorbol myristate acetate also did not enhance the bactericidal effect of neutrophils on PS-positive Strep. mutans. However, PS-positive Strep. mutans elicited oxygen-reactive products from neutrophils, 2-fold less than with PS-negative Strep. mutans. The results indicate that in situ production of bacterial extracellular polysaccharides might be a major virulence factor of Strep. mutans, enabling PS-positive Strep. mutans in the dental-plaque biofilm to evade killing by human neutrophils.

Objectives: The purpose of this study was to evaluate the antimicrobial efficacy of parabens, in a mouthwash and in a slow release device, against cariogenic bacteria in the oral cavity., Methods: Parabens were formulated in a mouthwash or in a topical slow release varnish preparation. In two separate studies, volunteers were asked to use the mouthwash or the slow release varnish applied in a personal night guard device. The levels of mutans streptococci (MS), Lactobacilli (LB) and total cultivated bacteria were measured before and after using the mouthwash or the slow release varnish., Results: The mouthwash containing parabens had a minor and a short-term effect on MS and LB counts in human saliva. The use of slow release varnish containing parabens, applied in a night guard, had a prolonged antibacterial effect on both MS and LB counts., Conclusions: Parabens in a mouthwash had little effect on oral bacteria counts; however, paraben in the slow release device had a significant and an extended effect in reducing oral bacteria. Although substantial reductions in oral bacterial counts were recorded after the use of parabens in a slow release device, this effect could probably be enhanced by an improved pharmaceutical formulation.

The prevalence of dental caries and periodontal treatment needs in an institutionalized population with Down syndrome was examined and the relationship between caries prevalence, salivary pH, and salivary levels of Streptococcus mutans was studied. Thirty-two children with Down syndrome, aged 8 to 13, were compared with two control groups of similar age ranges: healthy children and non-Down mentally retarded (MR) children living in the same institution as the Down syndrome population. The gender ratio mixtures in each group also matched the study sample. Caries experience as indicated by decayed, missing, and filled surfaces (DMF-S) showed significantly lower mean scores for the Down syndrome group compared with both control groups. A similar pattern was found when evaluating the mean numbers of decayed surfaces. Streptococcus mutans counts, expressed as number of colony-forming units on mitis salivarius agar plates among the Down syndrome group, were the lowest, although not statistically significant compared with the counts of the healthy children. Both groups had bacterial counts which were significantly lower than those of the MR group. Significant differences between the two institutionalized groups and the healthy group were recorded for the salivary pH levels. The periodontal treatment needs as evaluated by the Community Periodontal Index of Treatment Needs showed significant difference between the MR group versus both the healthy population and the Down syndrome group. On the whole, 84% of the Down syndrome children were cariesfree.

The suppression of S. mutans is a predominate factor in preventing tooth decay. Sustained-release-delivery varnish of chlorhexidine was applied to dental plastic shells and administered to eight volunteers to be worn while sleeping. Salivary bacterial samples were taken on days 0, 7, 14, 21, 28, 35. A statistically significant reduction in S. mutans counts was recorded during the course of the study while a non-significant reduction in the total bacterial counts was found. Our results indicate that the application of chlorhexidine in the form of slow-release varnish in plastic shells is an effective intraoral drug delivery system resulting in reduction of S. mutans.

The effect of a slow-releasing dosage (SRD) coating of chlorhexidine on the salivary levels of Streptococcus mutans and on plaque index scores in patients with removable partial dentures (RPD) was tested. The SRD proved to be effective in maintaining a low level of S. mutans counts after mechanical cleaning, as compared to a baseline established during the control period. Plaque index scores were lower following the treatment and correlated with the microbiological results. Our findings indicate that a single application of sustained-release chlorhexidine to removable partial dentures effectively maintains S. mutans levels as well as reducing the plaque score for a minimum period of 1 week.

The in vitro effect of lithium (Li) on growth and adherence of Streptococcus mutans 6715 in the presence and absence of sucrose was examined by means of optical density and transmission electron microscopy. In the non-sucrose assay, bacterial growth was depressed and adherence was elevated between concentrations of 1.44-11.52 mmol/L Li. At 7.20 mmol/L Li extracellular material was present on the bacterial wall. Using 11.52-28.08 mmol/L Li resulted in a perfect negative correlation between the increasing concentrations of Li and bacterial growth and adherence (rs = -0.9 and rs = -1, respectively) in both assays. This paper addresses the dichotomy between the low and high Li concentrations regarding the two bacterial parameters studied, as well as their possibly related cariogenic and cariostatic clinical relevance.

Streptococcus mutans colonizing on tooth surfaces is one of the major causative agents of human dental caries. Despite numerous studies conducted on lasers and oral tissue interactions, little is known about the effect of laser energy on S. mutans gene expression in a biofilm form. The aim of this study was to investigate the effect of sublethal energies of CO2 laser on biofilm and gene expression of the oral bacteria S. mutans immobilized in biofilm. S. mutans biofilm was irradiated with CO2 laser. Vitality and construction of the biofilm were observed by confocal laser scanning microscopy and scanning electron microscopy. The effect of laser irradiation on gene expression was evaluated by DNA microarray. CO2 laser irradiation had a dose effect on the viability of S. mutans immobilized in biofilm. A nonsignificant lethal effect was observed at 31 J/cm2 while at higher energy of 70 and 144 J/cm2 an antibacterial effect was recorded. The mode of antibacterial action seems to be from the inner layers toward the outer layer of the biofilm, indicating the influence of the surface on the killing effect. At 31 J/cm2, microarray analysis indicated a moderate effect on S. mutans gene expression due to CO2 laser irradiation, mainly down-regulating genes related to bacterial stress response. In conclusion, laser irradiation at sublethal energy had an effect on gene expression of S. mutans. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We have previously shown that the natural sweetener glycyrrhizin (glyc) inhibits in vitro adherence of Streptococcus mutans in the presence of sucrose. In order to further examine the mechanism of adherence inhibition, extracellular glucosyltransferase of S. mutans was obtained, and its ability to produce glucans from sucrose in the presence of glyc was tested. These results indicate that glyc inhibits bacterial adherence by affecting the activity of glucosyltransferase. [ABSTRACT FROM AUTHOR]

The ability of oral bacteria to adhere to surfaces is associated with their pathogenicity. Actinomyces can adhere to pellicle and cells through extracellular fimbriae. Research on adhesion of actinomyces has been conducted with use of hydroxyapatite (HA) coated with mammalian-derived salivary constituents, whereas the bacterial-derived components of the acquired pellicle have been largely ignored. The influence of the cell-free bacterial enzyme, glucosyltransferase (GTF), on adhesion of human and rodent isolates of Actinomyces viscosus was examined. Cell-free GTF was adsorbed onto parotid saliva-coated hydroxyapatite (sHA). Next, A. viscosus was exposed to the pellicle following the synthesis of glucan formed in situ by GTF. Glucans formed on the pellicle served as binding sites for adhesion of a rodent strain of A. viscosus. Conversely, the presence of in situ glucans on sHA reduced the adhesion of human isolates of A. viscosus compared with their adhesion to sHA. Adhesion of the rodent strains may be facilitated through a dextran- binding protein, since the rodent strains aggregated in the presence of dextrans and mutan. The human isolates were not aggregated by dextran or mutan. Pellicle harboring A. LiSCOSUS rodent strains interfered with the subsequent adhesion of Streptococcus mutans to the bacterial-coated pellicle. In contrast, the adhesion of S. mutans to pellicle was not decreased when the pellicle was pre-exposed to a human isolate of A. viscosus. The experimental data suggest that human and the rodent isolates of A. viscosuts have distinct glucan adhesion properties. Moreover, these results emphasize the role of in situ glucans in bacterial adhesion to the acquired pellicle by promoting selective adherence of bacteria or by masking potential binding sites for others. [ABSTRACT FROM AUTHOR]