Effect of sucrose in culture media on the location of glucosyltransferase of Streptococcus mutans and cell adherence to glass surfaces

The findings of glucosyltransferase enzymes derived from oral streptococci

Glucosyltransferase enzymes (Gtfs) distribute among some streptococcal species in oral cavity and are known as key enzymes contributing to the development of oral biofilm such as dental plaque. In 18 streptococcal species, 45 glucosyltransferase genes (gtf) are detected from genome database. Gtfs catalyze the synthesis of the glucans, which are polymers of glucose, from sucrose and they are main component of oral biofilm. Especially, the Gtfs from Streptococcus mutans are recognized as one of dental caries pathogens since they contribute to the formation of dental plaque and the establishment of S. mutans in the tooth surface. Therefore, Gtfs has been studied particularly by many researchers in the dentistry field to develop the anti- caries vaccine. However, it is not still accomplished. In these days, the phylogenetic and crystal structure analyses of Gtfs were performed and the study of Gtfs will enter new situation from the technique in the past old viewpoint. The findings from those analyses will affect the development of the anti-caries vaccine very much after this.　In this review, we summarize the findings of oral streptococcal Gtfs and consider the perspectives of the dental caries prevention which targeted Gtf.

A comprehensive review on mutan (a mixed linkage of α-1-3 and α-1-6 glucans) from bacterial sources

Mutan is an extracellular sticky polymer having α-1-3 and α-1-6 glycosidic linkages with a large diversity in molecular weights and structures depending on the source. These compounds are reported to be highly thermostable and also have potential physiochemical and biological applications. The main aim of this review is to provide an overview of glucosyltransferases and their role in mutan synthesis. The production strategies and structural properties of bacterial mutans are discussed with a goal to improve production efficiency. The physicochemical features, chemical modifications, potential industrial applications and future prospects are also discussed. According to data, mutan and its derivatives will play a larger role in medicinal sectors and as thermoplastics in the near future.Abbreviations: ABTS: 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid; BHI: Brain heart infusion broth; ¹³C (HSQC) NMR: Heteronuclear Single Quantum Coherence NMR; CBMs: Carbohydrate binding modules; DPPH: 2,2-diphenyl-1-picrylhydrazyl; FTIR: Fourier-transform infrared spectroscopy; GC-MS: Gas chromatography-mass spectrometry; GPC: Gel permeation chromatography; Gtfs: Glucosyltransferases; ¹H (DQF-COSY): Double-quantum filtered correlation spectroscopy; HPAEC-PAD: High-performance anion exchange chromatography with pulsed amperometric detection; HPLC: High performance liquid chromatography; HPSEC-RI: High-performance size exclusive chromatography coupled with refractive index; HPSEC-MALLS: High-performance size exclusive chromatography with multi-angle laser light scattering detection; MALDI-TOF: Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry; M_w: Weight-average molecular weight; MWD: Molecular weight distribution; NMR: Nuclear magnetic resonance spectroscopy; TEM: Transmission electron microscopy; THB: Todd Hewitt Broth; TTY: Tryticase tryptose yeast extract broth.

Biofilm and Foreign Body Infection the Significance to Capd-Associated Peritonitis

Microbial colonization of indwelling and implantable medical devices and prostheses is known to precede the formation of an adherent biofilm, such as is found on peritoneal catheters during CAPD. Micro-organismderived exopolysaccharides within the biofilm matrix seem to confer unique biological properties on this material, such as enhanced resistance to host defenses and antimicrobial agents. It has been proposed that an adherent biofilm is a major contributing factor in the development of foreign-body infections, including CAPD peritonitis. The source of organisms which lead to biofilm formation on peritoneal catheters is unknown but may include “seeding” at the time of surgical placement and migration from the subcutaneous tunnel via the inner cuff.

Strategies to inhibit biofilm development in industrial systems usually involve physical destruction of the biofilm and the use of biocides. Clinical success has been achieved by antimicrobial agents impregnated into or coated onto susceptible devices. Microbial adhesion to inanimate surfaces is a complex and multifaceted event. Continued research in this area, however, should increase our understanding of the factors involved underlying foreignbody infection.

Recent Progress of Basic Studies of Natural Products and Their Dental Application

The present article reviews the research progress of three major polyphenols (tannins, flavonoids and lignin carbohydrate complexes), chromone (backbone structure of flavonoids) and herbal extracts. Chemical modified chromone derivatives showed highly specific toxicity against human oral squamous cell carcinoma cell lines, with much lower toxicity against human oral keratinocytes, as compared with various anticancer drugs. QSAR analysis suggests the possible correlation between their tumor-specificity and three-dimensional molecular shape. Condensed tannins in the tea extracts inactivated the glucosyltransferase enzymes, involved in the biofilm formation. Lignin-carbohydrate complexes (prepared by alkaline extraction and acid-precipitation) and crude alkaline extract of the leaves of Sasa species (SE, available as an over-the-counter drug) showed much higher anti-HIV activity, than tannins, flavonoids and Japanese traditional medicine (Kampo). Long-term treatment with SE and several Kampo medicines showed an anti-inflammatory and anti-oxidant effects in small size of clinical trials. Although the anti-periodontitis activity of synthetic angiotensin II blockers has been suggested in many papers, natural angiotensin II blockers has not yet been tested for their possible anti-periodontitis activity. There should be still many unknown substances that are useful for treating the oral diseases in the natural kingdom.

Biofilm formation of beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates and its association with emm polymorphism

Biofilm formation has been well known as a determinant of bacterial virulence. Group G Streptococcus dysgalactiae subspecies equisimilis (SDSE), a relevant pathogen with increasing medical importance, was evaluated for the biofilm-forming potential. Microtiter plate assay was used to assess the most feasible medium for group G SDSE to form a biofilm. Among 246 SDSE isolates examined, 46.7%, 43.5%, 33.3%, and 26.4% of isolates showed moderate or strong biofilm-forming abilities using tryptic soy broth (TSB), brain heart infusion broth (BHI), Todd-Hewitt broth (THB), and C medium with 30 mM glucose (CMG), respectively. The addition of glucose significantly increased the biofilm-forming ability of group G SDSE. FCT (fibronectin-collagen-T-antigen) typing of SDSE was first undertaken and 11 FCT types were found. Positive associations of stG10.0 or negative associations of stG245.0, stG840.0, and stG6.1 with biofilm-forming ability of SDSE were, respectively, found. This was the first investigation demonstrating biofilm-forming potential in clinical group G SDSE isolates; also, some significant associations of biofilm-forming ability with certain emm types were presented.

Dextranase from Arthrobacter oxydans KQ11-1 inhibits biofilm formation by polysaccharide hydrolysis

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC₅₀ and MBRC₅₀) of dextranase were 2 U ml^-1 and 5 U ml^-1, respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.

Experimental Models of Oral Biofilms Developed on Inert Substrates: A Review of the Literature

The oral ecosystem is a very complex environment where more than 700 different bacterial species can be found. Most of them are organized in biofilm on dental and mucosal surfaces. Studying this community is important because a rupture in stability can lead to the preeminence of pathogenic microorganisms, causing dental decay, gingivitis, or periodontitis. The multitude of species complicates biofilm analysis so its reproduction, collection, and counting are very delicate. The development of experimental models of dental biofilms was therefore essential and multiple in vitro designs have emerged, each of them especially adapted to observing biofilm formation of specific bacteria within specific environments. The aim of this review is to analyze oral biofilm models.

Inhibitory effect of zingiber officinale towards Streptococcus mutans virulence and caries development: in vitro and in vivo studies

BACKGROUND

Streptococcus mutans is known as a key causative agent of dental caries. It metabolizes dietary carbohydrate to produce acids which reduce the environmental pH leading to tooth demineralization. The ability of this bacterium to tolerate acids coupled with acid production, allows its effective colonization in the oral cavity leading to the establishment of highly cariogenic plaque. For this reason, S. mutans is the only bacterium found in significantly higher numbers than other bacteria in the dental plaque. The aim of this study was to evaluate the effect of crude extract and methanolic fraction of Z. officinale against S. mutans virulence properties.

RESULTS

We investigated in vitro and in vivo activity of crude extract and methanolic fraction at sub- MIC levels against cariogenic properties of S. mutans. We found that these extracts strongly inhibited a variety of virulence properties which are critical for its pathogenesis. The biofilm formation in S. mutans was found to be reduced during critical growth phases. Furthermore, the glucan synthesis and adherence was also found to be inhibited. Nevertheless, the insoluble glucan synthesis and sucrose dependent adherence were apparently more reduced as compared to soluble glucan synthesis and sucrose- independent adherence. Biofilm architecture inspected with the help of confocal and scanning electron microscopy, showed dispersion of cells in the treated group as compared to the control. The Quantitative Real Time PCR (qRT-PCR) data had shown the down regulation of the virulence genes, which is believed to be one of the major reasons responsible for the observed reduction in the virulence properties. The incredible reduction of caries development was found in treated group of rats as compared to the untreated group which further validate our in vitro data.

CONCLUSION

The whole study concludes a prospective role of crude extract and methanolic fraction of Z. officinale in targeting complete array of cariogenic properties of S. mutans, thus reducing its pathogenesis. Hence, it may be strongly proposed as a putative anti- cariogenic agent.

Effect of sucrose concentration on sucrose-dependent adhesion and glucosyltransferase expression of S. mutans in children with severe early-childhood caries (S-ECC)

Sucrose, extracellular polysaccharide, and glucosyltransferases (GTFs) are key factors in sucrose-dependent adhesion and play important roles in the process of severe early-childhood caries (S-ECC). However, whether sucrose concentration regulates gtf expression, extracellular polysaccharide synthesis, and sucrose-dependent adhesion is related to the different genotypes of S. mutans isolated from ECC in children and still needs to be investigated. In this study, 52 strains of S. mutans were isolated from children with S-ECC and caries-free (CF) children. Water-insoluble glucan (WIG) synthesis was detected by the anthrone method, adhesion capacity by the turbidimetric method, and expression of gtf by RT-PCR in an in vitro model containing 1%–20% sucrose. The genotypes of S. mutans were analyzed by AP-PCR. The results showed that WIG synthesis, adhesion capacity, and gtf expression increased significantly when the sucrose concentration was from 1% to 10%. WIG synthesis and gtfB as well as gtfC expression of the 1% and 5% groups were significantly lower than those of the 10% and 20% groups (p < 0.05). There were no significant differences between the 10% and 20% groups. The fingerprints of S. mutans detected from individuals in the S-ECC group exhibited a significant difference in diversity compared with those from CF individuals (p < 0.05). Further, the expression of gtfB and gtfC in the S-ECC group was significantly different among the 1- to 5-genotype groups (p < 0.05). It can be concluded that sucrose-dependent adhesion might be related to the diversity of genotypes of S. mutans, and the 10% sucrose level can be seen as a “turning point” and essential factor for the prevention of S-ECC.

Inhibition of major virulence pathways of Streptococcus mutans by quercitrin and deoxynojirimycin: a synergistic approach of infection control

OBJECTIVES

To evaluate the synergistic effect of Quercitrin and Deoxynojirimycin (DNJ) together with their individual inhibitory effect against virulence pathways of Streptococcus mutans.

METHODOLOGY

MICs of both the compounds were determined by the microdilution method, followed by their in vitrosynergy using checkerboard and time kill assay. The nature of interaction was classified as synergistic on the basis of fractional inhibitory concentration index (FICI) value of ≤0.5. Furthermore, the activity of Quercitrin and DNJ was evaluated individually and in combination against various cariogenic properties of S. mutans UA159 such as acidogenesis, aciduracity, glucan production, hydrophobicity, biofilm and adherence. Moreover, expression of virulent genes in S. mutans was analysed by quantitative RT- PCR (qRT-PCR) and inhibition of F1F0-ATPase, lactate dehydrogenase and enolase was also evaluated. Finally, scanning electron microscopy (SEM) was used to investigate structural obliteration of biofilm.

RESULTS

The in vitro synergism between Quercitrin and DNJ was observed, with a FICI of 0.313. Their MIC values were found to be 64 μg/ml and 16 μg/ml respectively. The synergistic combination consistently showed best activity against all the virulence factors as compared to Quercitrin and DNJ individually. A reduction in glucan synthesis and biofilm formation was observed at different phases of growth. The qRT-PCR revealed significant downregulation of various virulent genes. Electron micrographs depicted the obliteration of biofilm as compared to control and the activity of cariogenic enzymes was also inhibited.

CONCLUSIONS

The whole study reflects a prospective role of Quercitrin and DNJ in combination as a potent anticariogenic agent against S. mutans.

A graphene/zinc oxide nanocomposite film protects dental implant surfaces against cariogenic Streptococcus mutans

Oral biofilms play a crucial role in the development of dental caries and other periodontal diseases. Streptococcus mutans is one of the primary etiological agents in dental caries. Implant systems are regularly employed to replace missing teeth. Oral biofilms accumulate on these implants and are the chief cause of dental implant failure. In the present study, the potential of graphene/zinc oxide nanocomposite (GZNC) against the cariogenic properties of Streptococcus mutans was explored and the anti-biofilm behaviour of artificial acrylic teeth surfaces coated with GZNC was examined. Acrylic teeth are a good choice for implants as they are low cost, have low density and can resist fracture. Microscopic studies and anti-biofilm assays showed a significant reduction in biofilm in the presence GZNC. GZNC was also found to be nontoxic against HEK-293 (human embryonic kidney cell line). The results indicate the potential of GZNC as an effective coating agent for dental implants by efficiently inhibiting S. mutans biofilms.

Structural diversity of streptococcal mutans synthesized under different culture and environmental conditions and its effect on mutanase synthesis

Streptococcal mutans synthesized under different conditions by growing cultures or by their glucosyltransferases were shown to exhibit a great structural and property diversity. Culturing and environmental factors causing structural differences in mutans were specified. All of the obtained biopolymers (76 samples) were water-insoluble and most of them (72) had a structure with a predominance of α-(1→3)-linked glucose (i.e., the content of α-(1→3)-linkages in the glucan was always higher than 50%, but did not exceed 76%). An exception were four glucans containing more than 50% of α-(1→6)-sequences. In these structurally unique mutans, the ratio of α-(1→3)- to α-(1→6)-bonds ranged from 0.75 to 0.97. Aside from one polymer, all others had a heavily branched structures and differed in the number of α-(1→3), α-(1→6), and α-(1→3,6) linkages and their mutual proportion. The induction of mutanase production in shaken flask cultures of Trichoderma harzianum by the structurally diverse mutans resulted in enzyme activities ranging from 0.144 to 1.051 U/mL. No statistical correlation was found between the total percentage content of α-(1→3)-linkages in the α-glucan and mutanase activity. Thus, despite biosynthetic differences causing structural variation in the mutans, it did not matter which mutan structures were used to induce mutanase production.

Efficacy of E. officinalis on the cariogenic properties of Streptococcus mutans: a novel and alternative approach to suppress quorum-sensing mechanism

The present study was focused on evaluating the potential of Emblica officinalis against cariogenic properties of Streptococcus mutans, a causative microorganism for caries. The effect of crude extract and ethanolic fraction from Emblica officinalis fruit was analysed against S. mutans. The sub-MIC concentrations of crude and ethanolic fraction of E. officinalis were evaluated for its cariogenic properties such as acid production, biofilm formation, cell-surface hydrophobicity, glucan production, sucrose-dependent and independent adherence. Its effect on biofilm architecture was also investigated with the help of confocal and scanning electron microscopy (SEM). Moreover, expression of genes involved in biofilm formation was also studied by quantitative RT- PCR. This study showed 50% reduction in adherence at concentrations 156 µg/ and 312.5 µg/ml of crude extract and ethanolic fraction respectively. However, the biofilm was reduced to 50% in the presence of crude extract (39.04 µg/ml) and ethanolic fraction (78.08 µg/ml). Furthermore, effective reduction was observed in the glucan synthesis and cell surface hydrophobicity. The qRT-PCR revealed significant suppression of the genes involved in its virulence. Confocal and scanning electron microscopy clearly depicted the obliteration of biofilm structure with reference to control. Hence, this study reveals the potential of E. officinalis fruit extracts as an alternative and complementary medicine for dental caries by inhibiting the virulence factors of Streptococcus mutans.

Enhancement of fluoride activity against Streptococcus mutans biofilms by a substance separated from Polygonum cuspidatum

Polygonum cuspidatum is a plant with spreading rhizomes and numerous reddish-brown stems that has been used in Korean folk medicine to improve oral hygiene. Nevertheless, there are no reports related to its possible effect on the virulence of dental biofilms. In this study, the ability of a fraction (F1) separated from P. cuspidatum, alone or in combination with fluoride, to disrupt virulence factors and the composition of Streptococcus mutans biofilms was examined. F1 was mainly composed of resveratrol, emodin and physcion (approximately 16.2%, 18.9% and 2.07% of the weight of F1, respectively). F1 showed inhibitory effects on acid production and F-ATPase activity of S. mutans in biofilms, and could enhance fluoride activity against acid production and acid tolerance of S. mutans in biofilms. When S. mutans biofilms were briefly treated with F1 (10 min, a total of five times), the biomass accumulation, water-insoluble polysaccharides and intracellular iodophilic polysaccharides were reduced. Furthermore, the fluoride activity against biomass accumulation was enhanced by F1. These results suggest that F1 may be useful in the control of dental biofilms and in improving the cariostatic properties of fluoride without increasing its exposure.

Role of glucosyltransferase B in interactions of Candida albicans with Streptococcus mutans and with an experimental pellicle on hydroxyapatite surfaces

Candida albicans and mutans streptococci are frequently detected in dental plaque biofilms from toddlers afflicted with early childhood caries. Glucosyltransferases (Gtfs) secreted by Streptococcus mutans bind to saliva-coated apatite (sHA) and to bacterial surfaces, synthesizing exopolymers in situ, which promote cell clustering and adherence to tooth enamel. We investigated the potential role Gtfs may play in mediating the interactions between C. albicans SC5314 and S. mutans UA159, both with each other and with the sHA surface. GtfB adhered effectively to the C. albicans yeast cell surface in an enzymatically active form, as determined by scintillation spectroscopy and fluorescence imaging. The glucans formed on the yeast cell surface were more susceptible to dextranase than those synthesized in solution or on sHA and bacterial cell surfaces (P < 0.05), indicating an elevated α-1,6-linked glucose content. Fluorescence imaging revealed that larger numbers of S. mutans cells bound to C. albicans cells with glucans present on their surface than to yeast cells without surface glucans (uncoated). The glucans formed in situ also enhanced C. albicans interactions with sHA, as determined by a novel single-cell micromechanical method. Furthermore, the presence of glucan-coated yeast cells significantly increased the accumulation of S. mutans on the sHA surface (versus S. mutans incubated alone or mixed with uncoated C. albicans; P < 0.05). These data reveal a novel cross-kingdom interaction that is mediated by bacterial GtfB, which readily attaches to the yeast cell surface. Surface-bound GtfB promotes the formation of a glucan-rich matrix in situ and may enhance the accumulation of S. mutans on the tooth enamel surface, thereby modulating the development of virulent biofilms.

Novel epitopic region of glucosyltransferase B from Streptococcus mutans

In the development of a component vaccine against caries, the catalytic region (CAT) and glucan-binding domain (GBD) of glucosyltransferase B (GtfB) from Streptococcus mutans have been employed as target antigens. These regions were adopted as primary targets because they theoretically include epitopes associated with enzyme function. However, their antigenicities have not been fully evaluated. Although there are many reports about successful vaccination using these components, the principle has not yet been put to practical use. For these reasons, we came to doubt the effectiveness of the epitopes in vaccine production and reevaluated the antigenic region of GtfB by using in silico analyses combined with in vitro and in vivo experiments. The results suggested that the ca. 360-amino-acid variable region (VR) in the N terminus of GtfB is more reactive than CAT and GBD. This region is S. mutans and/or GtfB specific, nonconserved among other streptococcal Gtfs, and of unknown function. Immunization using an adenovirus vector-borne DNA vaccine confirmed that VR is an epitope that shows promise for the development of a caries vaccine.

Adherence capacities of oral lactobacilli for potential probiotic purposes

The most abundantly used probiotic strains come from the genus Lactobacillus and only a few studies have investigated their role in oral health. Even if a positive correlation has been established between the saliva Lactobacillus count and dental caries, this genus is generally recognized as safe (GRAS). Moreover, lactobacilli could in some cases play a beneficial role by inhibiting the growth of some oral pathogenic bacteria. This activity could justify their use as probiotic. To establish the potential health benefit of probiotic candidates, appropriate in vitro tests are required, particularly on their adhesive capacity. The aim of this work was to investigate the adhesive properties and surface characteristics of 70 oral lactobacilli that could be used as probiotics for oral health. For this, three methods were used: biofilm formation on a glass surface and on saliva-coated hydroxyapatite discs and the microbial adhesion to solvent method. The results of the biofilm formed on glass surface showed 13 strains with an adhesion score equal to or higher than 3. 57/70 (81%) of the tested lactobacilli did not form any biofilm on glass surfaces. All of the 13 strains formed biofilms on HA discs. Among these 13 strains, 10/13 (77%) showed low surface hydrophobicity (0-35%) and 3/13 (23%) showed medium hydrophobicity (36-70%). Some of the selected strains showed potentially useful adhesive capacity. This work paves the way for the selection of probiotics that could be used for oral health purposes with the aim to reduce carious risk.

Effect of sodium fluoride on the virulence factors and composition of Streptococcus mutans biofilms

OBJECTIVE

This study aimed to evaluate the influence of NaF (2, 10, 50 and 125 ppm F(-)) on the virulence factors and composition of Streptococcus mutans biofilms.

METHODS

S. mutans UA159 biofilms were formed on saliva-coated hydroxyapatite discs. To assess the influence of NaF on the virulence factors of S. mutans biofilm cells, glycolytic pH drop, proton-permeability and F-ATPase activity assay were performed using 74 h old S. mutans biofilms. Glucosyltransferase (GTF) activity assay in suspension was also performed. To examine the influence of NaF on S. mutans biofilm composition, the biofilms were treated twice daily (5 min exposure/treatment) a total of five times during biofilm formation. After a total of 5 treatments, the biomass, colony forming unit (CFU) and polysaccharide composition of the treated 74h old S. mutans biofilms were analysed by microbiological and biochemical methods, and scanning electron microscopy.

RESULTS

NaF showed inhibitory effects on the acid production and acid tolerance of S. mutans biofilm cells at 10, 50 and 125 ppm F(-), compared to the vehicle control (P<0.05) and the treatments at these concentrations also affected the biomass, water-insoluble extracellular polysaccharides and intracellular iodophilic polysaccharides of the biofilms, compared to the vehicle control (P<0.05).

CONCLUSIONS

These results indicate that NaF (10, 50 and 125 ppm F(-)) has inhibitory effects on the virulence factors and composition of S. mutans biofilms, suggesting the potential use of these concentrations as an effective measure for controlling dental biofilms.

In vitro anti-bacterial and anti-adherence effects of natural polyphenolic compounds on oral bacteria

AIMS

To investigate the action of different polyphenolic compounds, extracted from red wine, grape marc and pine bark, on oral bacteria.

METHODS AND RESULTS

The anti-microbial activity of extracts was examined by determining the Minimal Inhibitory Concentration and Minimal Bactericidal Concentration using the macro dilution broth technique. Their effect on the adherence was tested on growing cells of Streptococcus mutans on a glass surface and on a multi-species biofilm grown on saliva-coated hydroxyapatite discs. The effect on glucosyltransferase activity was analysed through the reductions in the overall reaction rate and the quantity of insoluble glucan (ISG) synthesized. Pine bark and grape marc extracts were the most effective inhibitors of the multi-species biofilm formation and of the ISG synthesis.

CONCLUSION

The tested components showed an interesting anti-plaque activity in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is, to our knowledge, the first and the most complete report on the properties of wine and pine bark extracts that could be used for oral disease prevention purpose.

In vitro effects of a fraction separated from Polygonum cuspidatum root on the viability, in suspension and biofilms, and biofilm formation of mutans streptococci

Polygonum cuspidatum (Polygonaceae) has traditionally been used in folk medicine to control oral diseases. Nevertheless, there are no reports related to its possible effect on the diseases, particularly on biofilm-related diseases such as dental caries. In this study, we evaluated in vitro effects of a fraction separated from Polygonum cuspidatum root on the viability, in both suspension and biofilms, and the biofilm formation of mutans streptococci. The separated fraction (F1) showed bacteriostatic and bactericidal activity against mutans streptococci in suspension, with minimum inhibitory concentration (MIC) range of 31.3-250 microg/ml and minimum bactericidal concentration (MBC) range of 0.5-1 mg/ml. At a concentration of 1.5 mg/ml, F1 killed approximately 2 log(10)CFU/ml of Streptococcus mutans and Streptococcus sobrinus after 2h of exposure. In biofilms, F1 also inhibited the viability of Streptococcus mutans and Streptococcus sobrinus, dependent on the biofilm age, the concentration of F1, and the treatment time. Four hours of exposure to 1.5 mg/ml F1 reduced the viable counts of Streptococcus mutans and Streptococcus sobrinus by greater than 2 log(10)CFU/disc. Furthermore, at sub-MIC levels, F1 inhibited biofilm formation by Streptococcus mutans and Streptococcus sobrinus in a dose-dependent fashion. Based on the preliminary phytochemical analysis, the activity of F1 may be related to the presence of anthraquinones, cardiac glycosides, terpenoids, and phenolics. These results indicate that F1 is probably useful in the control of oral biofilms and subsequent dental caries development.

In vitro inhibitory effects of Polygonum cuspidatum on bacterial viability and virulence factors of Streptococcus mutans and Streptococcus sobrinus

OBJECTIVES

Polygonum cuspidatum has been used in Korean folk medicine to improve oral hygiene. This study was performed to evaluate the effects of methanol extract from root of P. cuspidatum (MEP) on bacterial viability and the virulence factors of Streptococcus mutans and Streptococcus sobrinus.

METHODS

To test the effects of MEP on bacterial viability, we determined the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against 20 bacterial strains, including S. mutans and S. sobrinus, using a micro-dilution assay. In case of S. mutans and S. sobrinus, the assays for time-kill and bacterial growth rate at sub-MIC concentrations were also performed. To determine effects of the extract on the virulence factors of S. mutans and S. sobrinus, the assays for sucrose-dependent adherence, water-insoluble glucan formation, glycolytic acid production, and acid tolerance were performed at sub-MIC levels. Phytochemical analysis for constituents of MEP was carried out.

RESULTS

MEP showed a broad antibacterial range (MIC 0.5-4 mg/ml). The MBC was two to four times higher than the MIC. The time-kill curves showed S. mutans and S. sobrinus were significantly killed after 1h of incubation. At sub-MIC levels, doubling times of S. mutans and S. sobrinus dose-dependently increased up to 211% and 123%, respectively. At sub-MIC levels, MEP also showed inhibitory effects on the virulence factors of S. mutans and S. sobrinus in a dose-dependent fashion. Phytochemical analysis revealed the presence of alkaloids, sterol/terpenes, tannins, flavonoids, and carbohydrates.

CONCLUSION

These data indicate that MEP has inhibitory effects on bacterial viability at higher concentrations (> or =MIC) and the virulence factors of S. mutans and S. sobrinus at sub-MIC concentrations, suggesting that it might be useful for the control of dental plaque formation and subsequent dental caries formation.

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

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

Guaijaverin – a plant flavonoid as potential antiplaque agent against Streptococcus mutans

AIMS

The aim of the present study was to investigate the anti-Streptococcus mutans activity and the in vitro effects of subminimal inhibitory concentrations of guaijaverin isolated from Psidium guajava Linn. on cariogenic properties of Strep. mutans.

METHODS AND RESULTS

Bioautography-directed chromatographic fractionation, yield biologically active compound, quercetin-3-O-alpha-l-arabinopyranoside (guaijaverin), from crude methanol extract of P. guajava. Growth-inhibitory activity of the compound against Strep. mutans of both clinical and type strain cultures was evaluated. The anti-Strep. mutans activity of the guaijaverin was found to be bacteriostatic, both heat and acid stable and alkali labile with the minimum inhibitory concentration (MIC) of 4 mg ml(-1) for MTCC 1943 and 2 mg ml(-1) for CLSM 001. The sub-MIC concentrations (0.0078-2 mg ml(-1)) of the guaijaverin were evaluated for its cariogenic properties such as acid production, cell-surface hydrophobicity, sucrose-dependent adherence to glass surface and sucrose-induced aggregation of Strep. mutans.

CONCLUSIONS

The active flavonoid compound, quercetin-3-O-alpha-l-arabinopyranoside (guaijaverin) demonstrated high potential antiplaque agent by inhibiting the growth of the Strep. mutans.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated the new growth-inhibitory compound guaijaverin against Strep. mutans and led to the acceptance of traditional medicine and natural products as an alternative form of health care.

In vitro and in vivo effects of isolated fractions of Brazilian propolis on caries development

Recently, two chemically different types of Brazilian propolis (type-3 and -12) were shown to have cariostatic properties. This study aimed to evaluate the influence of their isolated fractions on mutans streptococci viability, glucosyltransferases (GTFs) activity and caries development in rats. The ethanolic extracts of propolis (EEPs) were serially fractionated into hexane (H-fr), chloroform, ethyl acetate, and ethanol. The ability of the four fractions and EEP to inhibit Streptococcus mutans and Streptococcus sobrinus growth and adherence to a glass surface was examined. The effect on GTFs B and C activity was also determined. For the caries study, 60 Wistar rats infected with Streptococcus sobrinus were treated topically twice daily as follows: (1) EEP type-3, (2) H-fr type-3, (3) EEP type-12, (4) H-fr type-12, and (5) control. In general, the H-fr from both types of propolis showed the highest antibacterial activity and GTFs inhibition. Furthermore, the EEP and H-fr type-3 and -12 were equally effective in reducing dental caries in rats. The data suggest that the putative cariostatic compounds of propolis type-3 and -12 are mostly non-polar; and H-fr should be the fraction of choice for identifying further potentially novel anti-caries agents.

Optimization of conditions for the efficient production of mutan in streptococcal cultures and post-culture liquids

The strain Streptococcus sobrinus CCUG 21020 was found to produce water-insoluble and adhesive mutan. The factors influencing both stages of the mutan production, i.e. streptococcal cultures and glucan synthesis in post-culture supernatants were standardized. The application of optimized process parameters for mutan production on a larger scale made it possible to obtain approximately 2.2 g of water-insoluble glucan per 11 of culture supernate--this productivity was higher than the best reported in the literature. It was shown that some of the tested beet sugars might be successfully utilized as substitutes for pure sucrose in the process of mutan synthesis. Nuclear magnetic resonance analyses confirmed that the insoluble biopolymer synthesized by a mixture of crude glucosyltransferases was a mixed-linkage (1-->3), (1-->6)-alpha-D-glucan (the so-called mutan) with a greater proportion of 1,3 to 1,6 linkages.

Comparative analysis of Gtf isozyme production and diversity in isolates of Streptococcus mutans with different biofilm growth phenotypes

Streptococcus mutans is the main pathogenic agent of dental caries. Glucosyltransferases (Gtfs) produced by these bacteria are important virulence factors because they catalyze the extracellular synthesis of glucans that are necessary for bacterial accumulation in the dental biofilm. The diversity of GtfB and GtfC isozymes was analyzed in 44 genotypes of S. mutans that showed a range of abilities to form biofilms in vitro. Several approaches were used to characterize these isozymes, including restriction fragment length polymorphism analysis of the gtfB and gtfC genes, zymographic analysis of the identified GtfB and GtfC genotypes, and quantitation of isozyme production in immunoblot experiments with specific monoclonal antibodies. A high diversity of gtf genes, patterns of enzymatic activity, and isozyme production was identified among the isolates tested. GtfC and, to a lesser extent, GtfB were produced in significantly higher amounts by strains that had high biofilm-forming ability than by strains with low biofilm-forming ability. Biofilm formation was independent of the GtfB and GtfC genotype. Atypical strains that showed an apparent single Gtf isozyme of intermediate size between GtfB and GtfC were also identified. The results indicate that various expression levels of GtfB and GtfC isozymes are associated with the ability of distinct S. mutans genotypes to grow as biofilms, strengthening the results of previous genetic and biochemical studies performed with laboratory strains. These studies also emphasize the need to identify factors that control gtf gene expression.

Genotypic diversity and virulence traits of Streptococcus mutans in caries-free and caries-active individuals

The present study evaluated the relationship between clonal diversity and some virulence traits of Streptococcus mutans isolated from eight caries-free and eight caries-active subjects. A total of 155 S. mutans isolates from caries-free subjects and 144 isolates from caries-active subjects were obtained from samples of saliva, dental plaque and tongue surface and identified by PCR. The isolates were submitted to arbitrarily primed (AP)-PCR (OPA-2 and OPA-13) and multilocus enzyme electrophoresis (MLEE) to establish the genotypic diversity. Production of water-insoluble glucan (WIG) (monitored by SDS-PAGE), final pH of cultures and the ability of bacterial cells to adhere to smooth glass in the presence of sucrose were measured. High and comparable abilities of MLEE and AP-PCR were found to distinguish S. mutans genotypes, using Simpson's index of discrimination (0.971 and 0.968, respectively). The results showed a significant difference (P < 0.01) in the number of genotypes when caries-free and caries-active groups were compared by both fingerprinting methods used. Final pH (P = 0.32) and the percentage of adherence to a glass surface (P = 0.62) did not show differences between the two groups; however, the intensities of WIG bands from the caries-active group were greater than those from the caries-free group (P < 0.01). In addition, WIG was positively correlated with the ability of S. mutans to adhere to a glass surface (r = 0.34, P = 0.02) from caries-active subjects. These data showed that AP-PCR analysis and MLEE are both effective methods for assessing the genetic relatedness of S. mutans. Using these techniques, it was found that there is a larger number of genotypes of S. mutans with increased ability to synthesize WIG in caries-active individuals.

Purification of glucosyltransferase from cell-lysate of Streptococcus mutans by counter-current chromatography using aqueous polymer two-phase system

Counter-current chromatography (CCC) using a cross-axis coil planet centrifuge (X-axis CPC) was applied to the purification of glucosyltransferase (GTF) from a cell-lysate of cariogenic bacteria. The purification was performed using an aqueous polymer two-phase system composed of 4.4% (w/w) polyethylene glycol (PEG) 8000-6% (w/w) dextran T500 containing 10mM phosphate buffer at pH 9.2 by eluting the upper phase (UP) at 1.0ml/min. The bacterial GTF in the cell-lysate of Streptococcus mutans was selectively retained in the dextran-rich lower stationary phase. The column contents were diluted and subjected to hydroxyapatite (HA) chromatography to remove the polymers from the GTF. Fractions eluted with 500mM potassium phosphate buffer were analyzed by GTF enzymatic activity as well as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The GTF purity in the final product was increased about 87 times as that in the cell-lysate with a good recovery rate of about 79% through this purification process.

Hydroquinone, a control agent of agglutination and adherence of Streptococcus mutans induced by sucrose

Hydroquinone was found to alter agglutination of Streptococcus mutans induced by sucrose. The newly formed agglutination product produced by hydroquinone does not kill this cariogenic bacterium and the formation is reversible. The agglutination altering activity of hydroquinone seems to be specific for strains of S. mutans. As a result, hydroquinone inhibits sucrose-induced adherence of S. mutans.

Effect of a novel type of propolis and its chemical fractions on glucosyltransferases and on growth and adherence of mutans streptococci

Flavonoids have been considered the main biologically active components in propolis. However, a new variety of flavonoid-free propolis was recently found and chemically classified as type 6. Because it showed activity against oral microorganisms, this study evaluated the effects of the crude ethanolic extract of this propolis and its chemical fractions on the activity of purified glucosyltransferases (GTFs) and on the growth and adherence of mutans streptococci. The inhibitory effect of propolis extracts on GTF activities was determined either in solution or adsorbed onto saliva-coated hydroxyapatite. Streptococcus mutans Ingbritt 1600, Streptococcus sobrinus 6715, and two clinical isolates of each species were used for antibacterial assays. Susceptibilities to the test extracts were analyzed using the agar diffusion method and by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC); the effect on bacterial adherence to a glass surface was also assessed. The activity of GTFs in solution was effectively inhibited by the ethanolic extract of propolis type 6 (EEP) (>80% inhibition at 0.5 mg/ml), hexane, and chloroform fractions (60-90% inhibition at 100 microg/ml); their inhibitory effects on surface enzymes were less pronounced. The EEP, hexane, and chloroform fractions also showed significant antibacterial activity. The data showed that propolis type 6 remarkably reduced GTF activity and inhibited mutans streptococci growth and adherence; these biological activities are associated with its nonpolar components.

Cloning of the Streptococcus mutans gene encoding glucan binding protein B and analysis of genetic diversity and protein production in clinical isolates

Streptococcus mutans, the primary etiological agent of dental caries, produces several activities that promote its accumulation within the dental biofilm. These include glucosyltransferases, their glucan products, and proteins that bind glucan. At least three glucan binding proteins have been identified, and GbpB, the protein characterized in this study, appears to be novel. The gbpB gene was cloned and the predicted protein sequence contained several unusual features and shared extensive homology with a putative peptidoglycan hydrolase from group B streptococcus. Examination of gbpB genes from clinical isolates of S. mutans revealed that DNA polymorphisms, and hence amino acid changes, were limited to the central region of the gene, suggesting functional conservation within the amino and carboxy termini of the protein. The GbpB produced by clinical isolates and laboratory strains showed various distributions between cells and culture medium, and amounts of protein produced by individual strains correlated positively with their ability to grow as biofilms in an in vitro assay.

Effect of 3-hydroxymethylene-2-thioxopyrrolidine on growth of two species of mutans streptococci and their in vitro plaque formation

3-Hydroxymethylene-2-thioxopyrrolidine (HMTP), the major product derived from radish mustard oil, was studied for its activity to inhibit the growth of mutans streptococci, their in vitro plaque formation and their glucan production. The minimum inhibitory concentration (MIC) (800-1600 mg/l) of HMTP at pH 7.0 was reduced to 200 mg/l by lowering the medium pH to 5.0. A dose-dependent inhibition of in vitro plaque formation was observed at 200-800 mg/l dose of HMTP. Production of water-insoluble glucan (WIG) was effectively inhibited by 45-98%, depending on HMTP dose (200-800 mg/l), while only 22% inhibition of water-soluble glucan (WSG) production was observed at an 800 mg/l dose.

Utilization and acid production of beta-galactosyllactose by oral streptococci and human dental plaque

Beta-galactosyllactose is a trisaccharide containing the beta-galactosidic linkage at the nonreducing end. The purpose of this study was to determine whether certain oral streptococci could utilize four kinds of beta-galactosyllactoses. Three of four beta-galactosyllactoses were unable to support growth of the oral streptococci and to be a substrate for producing acid from the cell suspensions and dental plaque. 4'-beta-Galactosyllactose supported growth of Streptococcus sanguis ATCC 35105, ATCC 49298, Streptococcus mitis ATCC 15914, Streptococcus oralis ATCC 35037, ATCC 10557 and Streptococcus milleri 10707 and produced acid from dental plaque. Although beta-galactosidase activities were observed in all the strains, 4'-beta-galactosyllactose could not be used as a carbon source for the growth of mutans streptococci. Enzymes metabolizing 4'-beta-galactosyllactose were induced when S. oralis ATCC 10557 was cultured in medium containing galactose. These results suggested that 4'-beta-galactosyllactose could be as cariogenic as lactose if it is consumed frequently and retained for a long period in the mouth.

Inhibitory effects of apple polyphenols and related compounds on cariogenic factors of mutans streptococci

The inhibitory effects of apple polyphenols (APP) on the synthesis of water-insoluble glucans by glucosyltransferases (GTF) of streptococci of the mutans group and on the sucrose-dependent adherence of the bacterial cells were examined in vitro. APP markedly inhibited the activity of GTF purified from the cariogenic bacterial cells. However, APP showed no significant effect on the growth of the cariogenic bacteria. The strongest GTF inhibitors in APP were apple condensed tannins (ACT), a mixture of procyanidins. The 50% inhibitory doses of ACT against the GTF of S. sobrinus and that of S. mutans were 1.5 microgram/mL and 5 microgram/mL, respectively. The ACT efficacy largely depended upon the degree of polymerization. Interestingly, while the other polyphenols known to inhibit GTF such as tannic acid markedly inhibited salivary alpha-amylase activity, APP and ACT only scarcely inhibited that enzyme activity. This means that APP and ACT might selectively inhibit the bacterial GTF activity under oral conditions.

Caries inhibitory activity of cacao bean husk extract in in-vitro and animal experiments

Cacao bean husk extract (CBH) was examined for inhibitory effects on the caries-inducing properties of mutans streptococci in vitro and on caries development in specific pathogen-free Sprague-Dawley rats infected with mutans streptococci. CBH reduced the growth rate of almost all oral streptococci examined, which resulted in the reduction of acid production. Furthermore, insoluble glucan synthesis by the glucosyltransferases from Streptococcus mutans MT8148R and Streptococcus sobrinus 6715 was significantly inhibited by CBH. Hence, the sucrose-dependent cell adherence of mutans streptococci was also depressed by CBH. The administration of CBH in drinking water resulted in significant reductions of caries development and dental plaque accumulation in rats infected with either Strep. sobrinus 6715 or Strep. mutans MT8148R, and the minimum cariostatic concentration was 1.0 mg/ml. These results indicate that CBH possesses powerful anticariogenic potential.

Purification, characterization, and molecular analysis of the gene encoding glucosyltransferase from Streptococcus oralis

Streptococcus oralis is a member of the oral streptococcal family and an early-colonizing microorganism in the oral cavity of humans. S. oralis is known to produce glucosyltransferase (GTase), which synthesizes glucans from sucrose. The enzyme was purified chromatographically from a culture supernatant of S. oralis ATCC 10557. The purified enzyme, GTase-R, had a molecular mass of 173 kDa and a pI of 6.3. This enzyme mainly synthesized water-soluble glucans with no primer dependency. The addition of GTase markedly enhanced the sucrose-dependent resting cell adhesion of Streptococcus mutans at a level similar to that found in growing cells of S. mutans. The antibody against GTase-R inhibited the glucan-synthesizing activities of Streptococcus gordonii and Streptococcus sanguis, as well as S. oralis. The N-terminal amino acid sequence of GTase-R exhibited no similarities to known GTase sequences of oral streptococci. Using degenerate PCR primers, an 8.1-kb DNA fragment, carrying the gene (gtfR) coding for GTase-R and its regulator gene (rgg), was cloned and sequenced. Comparison of the deduced amino acid sequence revealed that the rgg genes of S. oralis and S. gordonii exhibited a close similarity. The gtfR gene was found to possess a species-specific nucleotide sequence corresponding to the N-terminal 130 amino acid residues. Insertion of erm or aphA into the rgg or gtfR gene resulted in decreased GTase activity by the organism and changed the colony morphology of these transformants. These results indicate that S. oralis GTase may play an important role in the subsequent colonizing of mutans streptoccoci.

In vitro antimicrobial activity of propolis and Arnica montana against oral pathogens

Arnica and propolis have been used for thousands of years in folk medicine for several purposes. They possess several biological activities such as anti-inflammatory, antifungal, antiviral and tissue regenerative, among others. Although the antibacterial activity of propolis has already been demonstrated, very few studies have been done on bacteria of clinical relevance in dentistry. Also, the antimicrobial activity of Arnica has not been extensively investigated. Therefore the aim here was to evaluate in vitro the antimicrobial activity, inhibition of adherence of mutans streptococci and inhibition of formation of water-insoluble glucan by Arnica and propolis extracts. Arnica montana (10%, w/v) and propolis (10%, w/v) extracts from Minas Gerais State were compared with controls. Fifteen microorganisms were used as follows: Candida albicans--NTCC 3736, F72; Staphylococcus aureus--ATCC 25923; Enterococcus faecalis--ATCC 29212; Streptococcus sobrinus 6715; Strep. sanguis--ATCC 10556; Strep. cricetus--HS-6; Strep. mutans--Ingbritt 1600; Strep. mutans--OMZ 175; Actinomyces naeslundii--ATCC 12104, W 1053; Act. viscosus OMZ 105; Porphyromonas gingivalis; Porph. endodontalis and Prevotella denticola (the last three were clinical isolates). Antimicrobial activity was determined by the agar diffusion method and the zones of growth inhibition were measured. To assess cell adherence to a glass surface, the organisms were grown for 18 h at 37 degrees C in test-tubes at a 30 degree angle. To assay water-insoluble glucan formation, a mixture of crude glucosyltransferase and 0.125 M sucrose was incubated for 18 h at 37 degrees C in test-tubes at a 30 degree angle. Arnica and propolis extracts (20 microl) were added to these tubes to evaluate the % of inhibition of cell adherence and water-insoluble glucan formation. The propolis extract significantly inhibited all the microorganisms tested (p < 0.05), showing the largest inhibitory zone for Actinomyces spp. The Arnica extract did not demonstrate significant antimicrobial activity. Cell adherence and water-insoluble glucan formation were almost completely inhibited by the propolis extract at a final concentration of 400 microg/ml and 500 microg/ml, respectively. The Arnica extract showed slight inhibition of the adherence of the growing cells (19% for Strep. mutans and 15% for Strep. sobrinus) and of water-insoluble glucan formation (29%) at these same concentrations. Thus, the propolis extract showed in vitro antibacterial activity, inhibition of cell adherence and inhibition of water-insoluble glucan formation, while the Arnica extract was only slightly active in those three conditions.

Production of glucosyltransferases by clinical mutans streptococcal isolates as determined by semiquantitative cross-dot assay

Forty-four clinical isolates of mutans streptococci were examined by a semiquantitative cross-dot assay for in vitro production of glucosyltransferases GTF-I, GTF-SI and GTF-S of Streptococcus mutans, and GTF-I of Strep. sobrinus, using monospecific antibodies. The isolates were obtained from 12 1.5- to 3-year old children, six caries-active and six caries-free, and from their mothers. The isolates were selected originally from 243 isolates and they represented 35 genetically distinct types as analysed by serotyping and ribotyping. 27 isolates were of serotype c, nine of serotype e and eight of serotype g. Mother child pairs shared nine ribotypes, suggesting vertical transmission. The results showed that, when cultured in Todd-Hewitt broth supplemented with 1% glucose, all Strep. mutans isolates produced GTF-I and GTF-S and all except two produced GTF-SI of Strep. mutans. All Strep. sobrinus isolates produced GTF-I of Strep. sobrinus. The Strep. mutans GTF-I, GTF-SI and GTF-S production of isolates exhibiting a different ribotype showed variability. The variability of GTF-SI and GTF-S production was less pronounced for serotype e isolates. The GTF-I production by Strep. sobrinus isolates did not vary. Transmitted strains produced the same levels of GTFs as strains that were distinct (not transmitted). Strep. mutans isolates of caries-active children produced the same levels of GTF-I and GTF-S, but tended to produce lower levels of GTF-SI than isolates of caries-free children. In conclusion, the results suggested that Strep. mutans isolates exhibiting a different ribotype often had differences in production of GTFs. However, no clear superiority of the high-producer over the low-producer strains was found in regard to their colonization or caries promotion in young children.

Streptococcus oralis previously identified as uncommon 'Streptococcus sanguis' in Behçet's disease

The relation between the biochemical and serological properties of 'Streptococcus sanguis' was studied to characterize the strains isolated from dental plaque of patients with Behçet's disease and controls. Seven reference and 100 clinical strains preserved by the Behçet's Disease Research Committee of Japan were identified using established criteria and differentiated with antisera against Strep. oralis ATCC 10557, Strep. sanguis ATCC 10556 and 'Strep. sanguis' ST7, compatible with the criteria. Uncommon serovars (serotypes) KTH-1 (= ATCC 49298), KTH-2 (= ATCC 49296), KTH-3 (= ATCC KTH-4 (= ATCC 49297) and B220 (serovar KTH-1) with both IgA1 protease and neuraminidase (sialidase) were identified as Strep. oralis, whereas common serovars ST3 with IgA1 protease alone and ST7 without both enzymes were identified as Strep. sanguis and Strep. gordonii, respectively. Isolates previously ranked as uncommon serovars were identified as Strep. oralis, whereas the rest ranked as common serovars were identified as the same species as those of the grouping strains. A soft-agar technique was available for species identification except for Strep. oralis serovar KTH-1 reacting with the antiserum against Strep. gordonii ST7. The frequency of isolation of Strep. oralis was higher in Behçet's disease (52%) than in controls (38%), but no difference was observed between the properties of the two groups of isolates. Strep. oralis virulence factors may be involved in breach the mucosal barrier in patients with specific reactivity to these antigens and inducing Behçet's disease.

Molecular and structural requirements of a lipoteichoic acid from Enterococcus hirae ATCC 9790 for cytokine-inducing, antitumor, and antigenic activities

Comparison was made between the immunobiological and antigenic properties of two lipoteichoic acid (LTA) fractions (LTA-1 and -2) from Enterococcus hirae ATCC 9790, their glycolipid portions, and synthetic compounds partially mimicking the above bacterial products. The more lipophilic LTA-2 fraction was capable of inducing serum tumor necrosis factor alpha and interleukin-6 in muramyldipeptide-primed mice and serum gamma interferon in those primed with Propionibacterium acnes. The LTA-2 fraction also induced tumor necrosis factor alpha, interleukin-6, and thymocyte-activating factor (essentially interleukin-1) in murine peritoneal macrophage cultures. Consecutive intravenous injections of muramyldipeptide and the LTA-2 fraction in Meth A fibrosarcoma-bearing BALB/c mice caused hemorrhagic necrosis and marked regression leading to complete regression of the tumor with no accompanying weakening or lethal effects. The LTA-2 fraction was at least 10,000-fold less pyrogenic in rabbits than a reference endotoxic lipopolysaccharide. The more hydrophilic LTA-1 fraction, on the other hand, showed at most marginal activity in the in vivo and in vitro assays. Natural glycolipids (NGL-1 and -2) which were prepared from a chloroform-methanol extract of Streptococcus pyogenes and E. hirae cells, and comparable in structure to the lipid moieties of the LTA-1 and -2 fractions, respectively, were practically inactive in all of the assays. None of the test synthetic compounds was immunobiologically active, although synthetic partial counterparts of the structure of LTA proposed by W. Fischer (Handb. Lipid Res. 6:123-234, 1990) reacted with murine monoclonal antibody TS-2, which was raised against OK-432, a penicillin-killed S. pyogenes preparation, and capable of neutralizing the cytokine-inducing activities of the LTA-2 fraction.

Properties of Leuconostoc mesenteroides B-512FMC constitutive dextransucrase

Leuconostoc mesenteroides B-512FMC, a constitutive mutant for dextransucrase, was grown on glucose, fructose, or sucrose. The amount of cell-associated dextransucrase was about the same for the three sugars at different concentrations (0.6% and 3%). Enzyme produced in glucose medium was adsorbed on Sephadex G-100 and G-200, but much less enzyme was adsorbed when it was produced in sucrose medium. Sephadex adsorption decreased when the glucose-produced enzyme was preincubated with dextrans of molecular size greater than 10 kDa. The release of dextransucrase activity from Sephadex by buffer (20 mM acetate, pH 5.2) was the highest at 28 degrees-30 degrees C. The addition of dextran to the enzyme stimulated dextran synthesis but had very little effect on the temperature or pH stability. Dextransucrase purified by ammonium sulfate precipitation, hydroxyapatite chromatography, and Sephadex G-200 adsorption did not contain any carbohydrate, and it synthesized dextran, showing that primers are not necessary to initiate dextran synthesis. The purified enzyme had a molecular size of 184 kDa on SDS-PAGE. On standing at 4 degrees C for 30 days, the native enzyme was dissociated into three inactive proteins of 65, 62, and 57 kDa. However, two protein bands of 63 and 59 kDa were obtained on SDS-PAGE after heat denaturation of the 184-kDa active enzyme at 100 degrees C. The amount of 63-kDa protein was about twice that of 59-kDa protein. The native enzyme is believed to be a trimer of two 63-kDa and one 59-kDa monomers.