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PubMed1981

A radioimmunoassay for serum and gingival crevicular fluid antibodies to a purified protein of Streptococcus mutans.

A solid-phase radioimmunoassay was developed to measure serum IgG antibodies to a purified protein antigen I/II prepared from Streptococcus mutans. The assay was specific to this antigen and significant binding of 125I-radiolabelled antiserum was found only in sera from rhesus monkeys immunized with the antigen I/II but not in sham-immunized monkeys or those immunized with streptococcal antigen III. A very significant correlation was found in serum IgG antibodies tested by the radioimmunoassay and an immunofluorescent technique (r = 0.88, P less than 0.001). The sensitivity of the double-layer radioimmunoassay was increased 10 times by the addition of a third antibody layer and this enabled gingival crevicular fluid antibodies to be measured. Comparison of paired samples of serum and crevicular fluid revealed a very significant correlation between IgG antibodies to streptococcal antigen I/II in the the two fluids (P less than 0.001). These findings suggest that serum antibodies can reach the tooth surface via gingival crevicular fluid.

Animals↗
PubMed1986

Isolation and mode of action of a cell-free bacteriocin (mutacin) from serotype g Streptococcus mutans MT3791.

A bacteriocin, mutacin MT3791, was isolated from the culture supernatant of a dialysate medium of Tryptose phosphate broth cultures of Streptococcus mutans MT3791 (serotype g), a clinical isolate from a carious lesion of a Japanese child. The mutacin was found to inhibit the growth of most indicator strains of S. mutans and S. salivarius by the drop assay method. The mutacin was purified 1,450 fold from culture supernatant of S. mutans MT3791 by 60% saturated ammonium sulfate precipitation, followed by ultracentrifugation at 300,000 X g for 18 h. Gel filtration studies using Sepharose 4B indicated that the mutacin was highly aggregated, but could be dissociated by addition of 1% (final concentration) Tween 80 or 6M urea. The mutacin was heat stable, but the activity was destroyed after autoclaving at 120 degrees C for 60 min. It was susceptible to the enzymatic action of papain and pronase, but not trypsin, lipase or nucleases. The mutacin was adsorbed to whole cells of most strains of S. mutans. Mutacin MT3791 was bactericidal for an indicator strain, S. mutans MT703R (serotype e). The mutacin inhibited the incorporation of isotope-labelled precursors of protein, DNA, and RNA. Furthermore, mutacin MT3791 selectively and markedly suppressed the growth of S. mutans present in the dental plaque obtained from active carious lesions in the teeth of children. Possible role of mutacin in vivo was discussed with special reference to oral microbial ecology.

Bacteriocins↗
PubMed1988

Bicarbonate-based dental powder, fluoride, and saccharin inhibition of dental caries associated with Streptococcus mutans infection of rats.

The effects of NaHCO3-based dental powder containing NaF and sodium saccharin on dental caries and Streptococcus mutans recoveries in rats were studied. Weanling specific-pathogen-free Osborne-Mendel (SPFOM) rats were inoculated with S. mutans NCTC-10449S. Four infected groups were topically treated with either demineralized water (DW), a dental powder suspended such that there was 1 part solid per 2 parts DW, 0.073% NaF, or a combination of 0.073% NaF and 0.5% Na-saccharin (Nas). NaF-supplemented DW (at 10 ppm F-) was provided to a 5th group of infected rats as a positive treatment control, but this group was otherwise untreated. A sixth but uninfected group was topically treated with DW. All topical treatments were given once for 1 min daily per rat, for 5 days per week. Animals' teeth were swabbed for recovery of 10449S and total recoverable flora. Recoveries of 10449S were lower from powder-treated rats than from DW-treated rats. This difference approached but did not reach statistical significance. Total caries scores were 51% lower for the dental powder, 36% lower for the topical NaF, 34% lower for the combined NaF-Nas, and 54% lower for the NaF-supplemented drinking water group, all p less than 0.001. While all of the treatments inhibited smooth-surface caries, the dental powder effects, like those for the combined NaF-Nas, and NaF drinking water, were evident in fissure tooth surfaces as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Enhanced (+)-catechin transglucosylating activity of Streptococcus mutans GS-5 glucosyltransferase-D due to fructose removal.

The (+)-catechin transglucosylating activities of several glucosyltransferases (GTFs) from the genus Streptococcus were compared. For this purpose, a mixture of four GTFs from Streptococcus sobrinus SL-1 and recombinant GTF-B and GTF-D from Streptococcus mutans GS-5 expressed in Escherichia coli were studied. It was shown that after removal of alpha-glucosidase activity, GTF-D transglucosylated catechin with the highest efficiency. A maximal yield (expressed as the ratio of moles of glucoside formed to moles of catechin initially added) of 90% was observed with 10 mM catechin and 100 mM sucrose (K(m), 13 mM) in 125 mM potassium phosphate, pH 6.0, at 37 degrees C. (1)H and (13)C nuclear magnetic resonance spectroscopy revealed the structures of two catechin glucosides, (+)-catechin-4'-O-alpha-D-glucopyranoside and (+)-catechin-4',7-O-alpha-di-D-glucopyranoside. Fructose accumulation during glucosyl transfer from sucrose to the acceptor competitively inhibited catechin transglucosylation (K(i), 9.3 mM), whereas glucose did not inhibit catechin transglucosylation. The addition of yeasts was studied in order to minimize fructose inhibition by means of fructose removal. For this purpose, the yeasts Pichia pastoris and the mutant Saccharomyces cerevisiae T2-3D were selected because of their inabilities to utilize sucrose. Addition of P. pastoris or S. cerevisiae T2-3D to the standard reaction mixture resulted in a twofold increase in the duration of the maximum GTF-D transglucosylation rate. The addition of the yeasts also stimulated sucrose utilization by GTF-D.

Catechin↗
PubMed1997

The role of the Streptococcus mutans glucosyltransferases in the sucrose-dependent attachment to smooth surfaces: essential role of the GtfC enzyme.

Previous results have indicated that the glucosyltransferase activities of mutans streptococci are required for sucrose-dependent colonization of tooth surfaces. We have constructed mutants of Streptococcus mutans GS5 that are altered in varying combinations of the three gtf genes present in this organism. A quantitative in vitro sucrose-dependent attachment system was used to demonstrate that the inactivation of the gtfC gene drastically reduced adherence to smooth surfaces. By contrast, inactivation of the gtfB gene resulted in a smaller, but significant, reduction in attachment while the gtfD mutant was only marginally affected. Furthermore, production of only the glucosyltransferase C enzyme allowed for attachment although at reduced levels compared to the wild-type organism. The results from reintroduction of single copies of each of the gtf genes into a mutant of strain GS5 lacking glucosyltransferase activity also demonstrated the crucial role of the glucosyltransferase C enzyme in colonization. These results suggest a unique role for the glucosyltransferase C enzyme in the sucrose-dependent colonization of tooth surfaces by S. mutans strains.

Bacterial Adhesion↗
PubMed1990

The effect of sustained release application of chlorhexidine on salivary levels of Streptococcus mutans in partial denture wearers.

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.

Chlorhexidine↗
PubMed1980

Size determination of Streptococcus mutans 10499 by laser light scattering.

We have performed three different optical experiments to determine the mean size of the bacterial strain Streptococcus mutans 10449, a microorganism with dimensions comparable to the wavelength of the light used in our experiments. The three optical measurements give size values which are consistent with one another and favorably comparable to the consistency we found in identical measurements on a test system of polystyrene spheres of dimensions similar to the bacteria. Homodyne time correlation and power spectrum spectroscopy both depend on the coherence and monochromaticity of laser light for the determination of the mean diffusion coefficient of the scatterers. The Stokes-Einstein equation then relates the diffusion constant to the cell size. Differential light scattering relies for the interpretation of experimental data on the classical theoretical analysis of the angular distribution of scattered light from a scattering object. The three methods yield mean values for the radius of S. mutans 10499 of 0.324 +/- 0.006 mum, 0.0325 +/- 0.007 mum, and 0.315 +/- 0.009 mum, respectively. However, since intensity correlation spectroscopy provides a direct measure of polydispersity, it would appear to be the preferred single measurement technique for size determination.

Lasers↗
PubMed2004

RegM is required for optimal fructosyltransferase and glucosyltransferase gene expression in Streptococcus mutans.

Glucosyltransferases (Gtfs) and fructosyltransferase (Ftf), and the exopolysaccharides they produce, facilitate bacterial adherence and biofilm formation, and enhance the virulence of Streptococcus mutans. In this study, we used continuous chemostat cultures and reporter gene fusions to study the expression of ftf and gtfBC in response to carbohydrate availability and pH, and to asses the role of a protein similar to catabolite control protein A (CcpA), RegM, in regulation of these genes. Expression of ftf was efficient at pH 7.0 and 6.0, but was repressed at pH 5.0 under glucose-excess conditions. At pH 7.0, ftf expression was 5-fold lower under glucose-limiting conditions than in cells growing with an excess of glucose. Expression of gtfBC was also sensitive, albeit to a lesser extent, to pH and glucose availability. Inactivation of regM resulted in decreases of as much as 10-fold in both ftf and gtfBC expression, depending on growth conditions. These findings reinforce the importance of pH and carbohydrate availability for expression of two primary virulence attributes of S. mutans and reveal a critical role for RegM in regulation of expression of both gtfBC and ftf.

Bacterial Proteins↗
PubMed2002

An iron-binding protein, Dpr, from Streptococcus mutans prevents iron-dependent hydroxyl radical formation in vitro.

The dpr gene is an antioxidant gene which was isolated from the Streptococcus mutans chromosome by its ability to complement an alkyl hydroperoxide reductase-deficient mutant of Escherichia coli, and it was proven to play an indispensable role in oxygen tolerance in S. mutans. Here, we purified the 20-kDa dpr gene product, Dpr, from a crude extract of S. mutans as an iron-binding protein and found that Dpr formed a spherical oligomer about 9 nm in diameter. Molecular weight determinations of Dpr in solution by analytical ultracentrifugation and light-scattering analyses gave values of 223,000 to 292,000, consistent with a subunit composition of 11.5 to 15 subunits per molecule. The purified Dpr contained iron and zinc atoms and had an ability to incorporate up to 480 iron and 11.2 zinc atoms per molecule. Unlike E. coli Dps and two other members of the Dps family, Dpr was unable to bind DNA. One hundred nanomolar Dpr prevented by more than 90% the formation of hydroxyl radical generated by 10 microM iron(II) salt in vitro. The data shown in this study indicate that Dpr may act as a ferritin-like iron-binding protein in S. mutans and may allow this catalase- and heme-peroxidase-deficient bacterium to grow under air by limiting the iron-catalyzed Fenton reaction.

Bacterial Proteins↗
PubMed1985

Distinct bacteriocin groups correlate with different groups of Streptococcus mutans plasmids.

A correlation between the presence of 5.6-kilobase plasmids and bacteriocin activity was found in human-derived strains of Streptococcus mutans. Compared with bacteriocin activity of randomly selected clinical isolates of plasmid-negative strains, bacteriocin activity of plasmid-positive strains significantly inhibited not only two laboratory strains of S. mutans, OMZ176 and AHT (P less than 0.0001 and P = 0.038, respectively), but most plasmid-negative clinical isolates as well (P = 0.0005). Comparisons of inhibition between pairs of plasmid-positive strains revealed two groups, group I and group II, that produced distinct bacteriocins we designated as mutacin I and mutacin II, respectively. Within each group, a strain produced inhibitory activity against all the members of the other group but against no members of its own group. Plasmid DNA from plasmid-positive strains of each group was isolated and analyzed by restriction endonuclease digestion. Plasmids from the two groups that were apparently identical in size differed in digestion patterns for EcoRI, HaeIII, and TaqI, even though six TaqI fragments appeared to be common to all. Based on bacteriocin profiles and restriction enzyme digests, two distinct groups of plasmid-positive S. mutans strains emerged. Although the bacteriocin activity of plasmid-positive strain LM7 (serotype e) placed it in group I, clear differences in restriction digests distinguished it from the other plasmid-containing strains.

Bacteriocins↗
PubMed1980

Growth inhibition of Streptococcus mutans strain OMZ 176 by xylitol.

The present study showed that xylitol exhibited a dose-related inhibition of the growth of Streptococcus mutans in a Brain Heart Infusion medium. It is suggested that the mechanism involved may be an effect of the translocation of glucose across the bacterial cell membrane. Sorbitol showed no similar effect but caused a delay in the reaching of the stationary phase.

Culture Media↗
PubMed2001

uvrA is an acid-inducible gene involved in the adaptive response to low pH in Streptococcus mutans.

The pH-inducible acid tolerance response (ATR) is believed to play a major role in acid adaptation and virulence of Streptococcus mutans. To study this phenomenon in S. mutans JH1005, differential display PCR was used to identify and clone 13 cDNA products that had increased expression in response to pH 5.0 compared to that of pH 7.5-grown cells. One of these products, confirmed to be pH inducible by RNA dot blot and reverse transcription-PCR analyses, had 67% identity to a uvrA-UV repair excinuclease gene in Bacillus subtilis. Further sequence analysis of the uvrA homologue using the S. mutans genome database revealed that the complete gene was encoded in an open reading frame (ORF) of 2,829 bp (944 amino acids; 104.67 kDa). Immediately 3' of uvrA was an ORF encoding a putative aminopeptidase gene (pepP). uvrA knockouts were constructed in S. mutans strains JH1005, NG8, and UA159 using allelic-exchange mutagenesis, replacing the entire gene with an erythromycin resistance cassette. As with uvrA mutants in other bacteria, the S. mutans uvrA mutants were extremely sensitive to UV irradiation. The uvrA mutant of S. mutans JH1005 was also more sensitive than the wild type to growth at pH 5.0, showing a 15% reduction in growth rate and a 14% reduction in final resting culture density. Acid-adapted S. mutans JH1005 uvrA mutants were shown to be more resistant to UV irradiation than was the parent but were unable to survive exposure to a killing pH of 3.0. Moreover, agarose gel electrophoretic analysis of chromosomal DNA isolated from uvrA-deficient cells exposed to low pH demonstrated more DNA damage than that for the wild-type strain. Here we suggest that uvrA and the nucleotide excision repair pathway are involved in the repair of acid-induced DNA damage and are associated with successful adaptation of S. mutans to low pH.

Acids↗
PubMed1988

Streptococcus mutans counts obtained by a dip-slide method in relation to caries frequency, sucrose intake and flow rate of saliva.

The level of Streptococcus mutans in saliva was determined by a dip-slide method in 841 13-year-old children in order to identify children with high caries risk. For each child, the flow rate of saliva was determined. Caries scores were obtained from Public Dental Health records. A sucrose intake score was calculated based on self-reported frequency of intake of six types of sugary products. As S. mutans counts increased, there was a significant trend of increased DMFS and DS scores. No linear correlation was observed between reported intake of sucrose and S. mutans counts, but the children with the highest counts (class 3) tended to have significantly higher sucrose intake than the rest of the children. The flow rate of saliva decreased significantly as S. mutans increased.

Adolescent↗
PubMed1994

Identification of amino acid residues in Streptococcus mutans glucosyltransferases influencing the structure of the glucan product.

The glucosyltransferases (GTFs) of mutans streptococci are important virulence factors in the sucrose-dependent colonization of tooth surfaces by these organisms. To investigate the structure-function relationship of the GTFs, an approach was initiated to identify amino acid residues of the GTFs which affect the incorporation of glucose residues into the glucan polymer. Conserved amino acid residues were identified in the GTF-S and GTF-I enzymes of the mutans streptococci and were selected for site-directed mutagenesis in the corresponding enzymes from Streptococcus mutans GS5. Conversion of six amino acid residues of the GTF-I enzyme to those present at the corresponding positions in GTF-S, either singly or in multiple combinations, resulted in enzymes synthesizing increased levels of soluble glucans. The enzyme containing six alterations synthesized 73% water-soluble glucan in the absence of acceptor dextran T10, while parental enzyme GTF-I synthesized no such glucan product. Conversely, when residue 589 of the GTF-S enzyme was converted from Thr to either Asp or Glu, the resulting enzyme synthesized primarily water-insoluble glucan in the absence of the acceptor. Therefore, this approach has identified several amino acid positions which influence the nature of the glucan product synthesized by GTFs.

Amino Acid Sequence↗
PubMed2006

Triclosan inhibition of membrane enzymes and glycolysis of Streptococcus mutans in suspensions and biofilms.

Triclosan was found to be a potent inhibitor of the F(H+)-ATPase of the oral pathogen Streptococcus mutans and to increase proton permeabilities of intact cells. Moreover, it acted additively with weak-acid transmembrane proton carriers, such as fluoride or sorbate, to sensitize glycolysis to acid inhibition. Even at neutral pH, triclosan could inhibit glycolysis more directly as an irreversible inhibitor of the glycolytic enzymes pyruvate kinase, lactic dehydro genase, aldolase, and the phosphoenolpyruvate:sugar phosphotransferase system (PTS). Cell glycolysis in suspensions or biofilms was inhibited in a pH-dependent manner by triclosan at a concentration of about 0.1 mmol/L at pH 7, approximately the lethal concentration for S. mutans cells in suspensions. Cells in intact biofilms were almost as sensitive to triclosan inhibition of glycolysis as were cells in suspensions but were more resistant to killing. Targets for irreversible inhibition of glycolysis included the PTS and cytoplasmic enzymes, specifically pyruvate kinase, lactic dehydrogenase, and to a lesser extent, aldolase. General conclusions are that triclosan is a multi-target inhibitor for mutans streptococci, which lack a triclosan-sensitive FabI enoyl-ACP reductase, and that inhibition of glycolysis in dental plaque biofilms, in which triclosan is retained after initial or repeated exposure, would reduce cariogenicity.

Anti-Infective Agents, Local↗
PubMed1992

Epidemiological survey of Streptococcus mutans in a group of adult patients living in Pisa (Italy).

An epidemiological investigation was carried out to evaluate the prevalence of Streptococcus mutans in a group of 134 adult patients. Markedly higher frequency of isolation was observed in caries-active subjects than in caries-inactive or caries-free subjects, indicating a significant association between the prevalence of the microorganism and the caries status. Moreover, the presence of the microorganism appeared to have a significant association with the extent of caries experience evaluated by the DMF score. These findings are in agreement with those reported previously for school children in other areas of Italy. Isolation of S. mutans was compared among patients groups with different caries activity in relation to culture times of dental plaque samples in a transport medium (Colorimetric Broth Medium). S. mutans was most frequently isolated from caries-active subjects when the medium was incubated for 48 h after inoculation with dental plaque samples.

Adolescent↗