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PubMed1974

Some Immunochemical Properties of Dextransucrase and Invertase from Streptococcus mutans.

Dextransucrase and invertase of some strains of Streptococcus mutans were examined by immunodiffusion with antisera against enzymes purified from strain HS-6 (Bratthall's serotype a). Both antisera cross-reacted with crude enzyme preparations from the other serotype a (strains HS-1 and AHT) and d organisms (strains KIR, OMZ176, and OMZ65) but not with those from serotype b (strains FA-1 and BHT) or c organisms (strains GS-5, Ingbritt, and NCTC 10449). Based upon the antiserum used, the orders of antigenic similarity of the cross-reacting enzymes to the HS-6 enzymes were HS-6 > HS-1 > AHT = KIR = OMZ176 = OMZ65 for dextransucrase and HS-6 = HS-1 > AHT = KIR = OMZ176 = OMZ65 for invertase. It was found that the enzymes from serotype a organisms were not always antigenically homogeneous, as seen between strains HS-6, HS-1, or AHT for dextransucrase, and between the HS group and strain AHT for invertase. Antiserum against the HS-6 dextransucrase markedly inhibited the heterologous dextransucrases of serotype a organisms with the exception of strain HS-1 and d organisms, with or without the addition of dextran.

Journal Article↗
PubMed2002

Real-time PCR for quantification of Streptococcus mutans.

A real-time polymerase chain reaction (PCR) assay was developed for the quantification of Streptococcus mutans. Primers targeting gtf genes of S. mutans were designed and tested for their specificity using 28 oral streptococcal strains, three other bacterial strains, and human DNA. The primers could amplify specifically the target DNA fragment from a mixture of oral streptococcus genomic DNA containing about 10 fg to 10 ng of S. mutans genome DNA. The real-time PCR produced a linear quantitative detection range over concentrations spanning seven exponential values, with a detection limit of a few copies of S. mutans' genomic DNA per reaction tube. The results of the real-time PCR assay corresponded well to those of conventional culture assays for S. mutans in saliva samples. A real-time PCR assay for Streptococcus sobrinus and Streptococcus downei was also established and produced results that corresponded well to those from conventional culture assays for S. sobrinus in saliva samples. These assays will be useful as a new means to assess one of the important risk factors for caries.

Bacterial Typing Techniques↗
PubMed2000

Role of the dpr product in oxygen tolerance in Streptococcus mutans.

We have previously identified and characterized the alkyl hydroperoxide reductase of Streptococcus mutans, which consists of two components, Nox-1 and AhpC. Deletion of both nox-1 and ahpC had no effect on the sensitivity of S. mutans to cumene hydroperoxide or H(2)O(2), implying that the existence of another antioxidant system(s) independent of the Nox-1-AhpC system compensates for the deficiency. Here, a new antioxidant gene (dpr for Dps-like peroxide resistance gene) was isolated from the S. mutans chromosome by its ability to complement an ahpCF deletion mutant of Escherichia coli with a tert-butyl hydroperoxide-hypersensitive phenotype. The dpr gene complemented the defect in peroxidase activity caused by the deletion of nox-1 and ahpC in S. mutans. Under aerobic conditions, the dpr disruption mutant carrying a spectinomycin resistance gene (dpr::Spc(r) mutant) grew as well as wild-type S. mutans in liquid medium. However, the dpr::Spc(r) mutant could not form colonies on an agar plate under air. In addition, neither the dpr::Spc(r) ahpC::Em(r)::nox-1 triple mutant nor the dpr::Spc(r) sod::Em(r) double mutant was able to grow aerobically in liquid medium. The 20-kDa dpr gene product Dpr is an iron-binding protein. Synthesis of Dpr was induced by exposure of S. mutans cells to air. We propose a mechanism by which Dpr confers aerotolerance on S. mutans.

Aerobiosis↗
PubMed1978

Streptococcus mutans, an assessment of its physiological potential in relation to dental caries.

Streptococcus mutans converts low levels of sucrose to lactic acid, but at high levels favours synthesis of glucans for plaque accumulation. Thus, the continued exposure to sucrose fluxes would select microorganisms in the oral cavity (S. mutans being a prototype) with highly specialized adaptation and potential dental caries activity. The bacteria that have evolved physiological systems to function efficiently under these conditions are the lactic acid bacteria. These organisms survive in environments where carbohydrate availability is constantly changing. High tolerances to acidic environments may be an important determinant in establishing the ecology of the carious lesion. Also, the intercellular polysaccharide storgae (glycogenamylopectin) and extracellular polymer reserves (levan and soluble glucan) are important during carbohydrate depletion. Further, the formation of insoluble glucans is a prerequisite for the caries process on smooth surfaces of teeth through plaque development. These conditions could result in an increase in S. mutans and cariogenic microorganisms. As a result, this process may be best understood as a manifestation of an amphibiotic shift.

Carbohydrate Metabolism↗
PubMed1996

Deletion and reintroduction of glucosyltransferase genes of Streptococcus mutans and role of their gene products in sucrose dependent cellular adherence.

Streptococcus mutans has three kinds of glucosyltransferases (GTases), i.e. GTase-I, GTase-SI and GTase-S. These enzymes co-operatively synthesize adhesive glucan from sucrose, which contributes to firm adherence of growing organisms to solid surfaces. In this study, the genes encoding GTase-I (gtfB) and GTase-SI (gtfC) of S. mutans MT8148 (serotype c) were inactivated by the insertion mutagenesis by allelic exchange. Three types of isogenic mutants lacking either GTase-I, GTase-SI or both, respectively were isolated. Sucrose dependent cellular adherence of these mutants were significantly lower than that of the parent. Adherence of GTase-SI deficient mutant was lower than that of GTase-I deficient mutant. We then generated Escherichia coli-Streptococcus shuttle vectors carrying the gtfB and gtfC gene. The shuttle vector containing the gtfB gene was transformed into the GTase-I deficient mutant. Western blot analysis of the transformant revealed that GTase-I protein was fully expressed. Sucrose dependent adherence of the transformant increased but did not reach that of the parent. Similarly, the shuttle vector containing the gtfC gene was transformed into the GTase-SI deficient mutant. The expression of GTase-SI and sucrose dependent adherence of the transformant was revealed to be at a level similar to those by the parent. These results indicated that GTase-SI does play an essential role in the production of adhesive glucan that can lead to firm cellular adherence to solid surfaces.

Bacterial Adhesion↗
PubMed1979

Inhibition of complement-mediated lysis of sheep erythrocytes by cell-free preparations from Streptococcus mutans BHT.

A cell-free extract from the spent medium of Streptococcus mutans BHT was tested for anti-complementary activity with sheep erythrocytes (E) as target cells. It was determined that this extract was enriched for extracellular lipoteichoic acid (LTA) and that the LTA bound to the surfaces of sheep E. Furthermore, sheep E, sheep E plus antibodies (EA), and sheep cells in the intermediate stage of complement (C) component fixation EAC14 became refractory to C-mediated lysis after treatment with the LTA-rich extract. Sheep E in the intermediate states EAC142 and EAC1423567 were unaffected despite the fact that LTA could be detected on the surfaces of these cells with the passive hemagglutination procedure. Preliminary results showed that the C inhibitory activity co-purified with LTA, and LTA (both crude and purified) from other bacteria were anticomplementary. Both crude extracellular material from S. mutans BHT and partially purified extracellular LTA from the same bacteria caused consumption of whole human C activity.

Animals↗
PubMed1983

Characterization of serological cross-reactivity between polysaccharide antigens of Streptococcus mutans serotypes c and d.

Immunological assays with antisera prepared against purified Streptococcus mutans serotype c polysaccharide demonstrated that a cross-reacting determinant on c polysaccharide reacted with the wall-associated rhamnose-glucose polysaccharide from S. mutans serotype d. Studies with 60 antisera prepared against chemostat cultures of S. mutans Ingbritt (c) demonstrated that the rhamnose-glucose polysaccharide cross-reactive determinant was consistently expressed on c antigen under a variety of growth conditions.

Cell Wall↗
PubMed2006

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin.

BACKGROUND AND OBJECTIVES: A reliable method to eradicate the bacteria of residual carious dentin has not yet been developed. The aim of this study was to evaluate the antibacterial effect of a diode laser on Streptococcus mutans through different thickness (500, 1,000, and 2,000 microm) of human dentin. The thermal effect of laser irradiation was also investigated. STUDY DESIGN/MATERIALS AND METHODS: Dentin specimens were inoculated with 2 microl of S. mutans on one side and irradiated by a diode laser on the other side with a power output ranging from 0.5 to 7 W. The laser tip was swept with the whole irradiation area of 7 mm x 3 mm at a speed of about 10 mm/second with a total irradiation time of 30 seconds. Cooling with distilled water (30 ml/minute) was applied simultaneously during laser irradiation. After laser irradiation, the bacteria was removed from the dentin surfaces and cultured for 48 hours at 37 degrees C anaerobically to assess the colony forming units (CFU) per ml. The morphology of the lased bacteria and the temperature rise during laser irradiation were observed by scanning electron microscope (SEM) and measured by thermocouple, respectively. RESULTS: The results revealed that 7 W of laser power could kill 97.7% of CFU through 500 microm thickness of dentin. However, the bactericidal efficiency was significantly reduced as the dentin thickness was increased. The morphological changes of lased bacteria ranged from less affected such as loss of their wall bands and existence of minicells to more severely degenerated, such as disintegration and fusion of cells with pores on the cell wall. Only the dentin specimens with a thickness of 500 microm exhibited a temperature rise greater than 5.5 degrees C after receiving 5 or 7 W of laser irradiation. CONCLUSIONS: A diode laser can eliminate the Streptococcus mutans of the residual carious dentin without inducing high pulpal temperature rise when the remaining dentin thickness is greater than 1 mm.

Dental Caries↗
PubMed2006

Synergic antibacterial effect between visible light and hydrogen peroxide on Streptococcus mutans.

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.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Inhibitory effect of mouthwashes on Streptococcus mutans growth].

The efficacy of 10 mouthwashes available in Bangkok in inhibiting Streptococcus mutans growth in vitro was studied. After one-minute incubation with the bacterium, most mouthwashes, at concentrations recommended by the manufacturers, demonstrated the antimicrobial effect; three exhibited a complete while five a partial but varying degree of inhibition. Only two mouthwashes were found that did not significantly show any detrimental effect on the bacterial viability.

Mouthwashes↗
PubMed1997

[Ultrastructure of adherence of Streptococcus mutans MT8148 and its glucosyltransferase deficient mutants].

The ultrastructure of adherence of Streptococcus mutans MT8148 and its glucosyltransferase deficient mutants were compared by Scanning Electronic Microscope. Four patterns of adherence of tested strains in the presence of sucrose were observed. These results suggest that the cell-associated GTase is responsible for firm aggregation of cells. However, cell free GTase is also important in aggregation between cells.

Bacterial Adhesion↗
PubMed1979

Bacteriocinogeny and antibiotic resistance of naturally occurring strains of Streptococcus mutans.

We studied bacteriocinogenies and antibiotic resistances of naturally occurring strains of Streptococcus mutans isolated from different sources. It was found that naturally occurring strains from humans and rats were distinguished by their bacteriocin susceptibilities and production. We had a few incidences of tetracycline resistant strains only among those isolated from rats. It is quite interesting that none of the resistant strains we collected produced bacteriocins.

Animals↗
PubMed1979

Phenotypic stability of the cell wall of Streptococcus mutans Ingbritt grown under various conditions.

Quantitative analyses of cell walls from Streptococcus mutans Ingbritt grown under carbohydrate limitation in the chemostat showed that growth conditions had no statistically significant effect on the composition of polysaccharide, peptidoglycan, or the proportion of polysaccharide in the cell wall. Lysis of cell wall preparations with a muramidase supported this conclusion and further indicated that there was little difference in their overall structure. In contrast, there was a consistent difference between the rates of lysis by this enzyme of organisms grown in 0.2% glucose and 0.5% glucose. Extremes of pH or dilution rate essentially did not influence the immunogenicity of type c antigen in whole organisms irrespective of whether the carbohydrate source was glucose or sucrose. However, differences were found in the immunogenicity of lipoteichoic acid under similar circumstances. The results indicated there was an inherent phenotypic stability in the cell walls of S. mutans Ingbritt despite changes in pH, generation time, and carbohydrate source, and that any changes that did occur were probably due to associated cell-surface components.

Alanine↗
PubMed2004

Further characterization of immunomodulation by a monoclonal antibody against Streptococcus mutans antigen P1.

We demonstrated previously that mucosal immunization of mice with Streptococcus mutans coated with the monoclonal antibody (MAb) 6-11A directed against the major surface adhesin protein P1 results in changes in the amount, isotype distribution, and specificity of serum antibodies compared with animals immunized with bacteria only. We now show that the specificity of the mucosal secretory IgA response was also influenced by this MAb. Changes in antibody specificity were associated with changes in biological activity. Serum samples which differed in antibody reactivity with P1 polypeptides generated by partial digestion with N-chlorosuccinimide but not in isotype distribution or overall reactivity with S. mutans or intact P1 demonstrated a statistically significant difference in the ability to inhibit bacterial adherence to salivary-agglutinin-coated hydroxyapatite beads. Serum IgG antibodies against P1 from mice immunized with either S. mutans alone or S. mutans coated with 6-11A were shown to recognize antigenic determinants dependent on the presence of the central proline-rich repeat domain, a segment necessary for the structural integrity of the molecule. However, no statistically significant differences were observed in antibody reactivity with a panel of six partial P1 polypeptides encoded by overlapping spaP subclones, suggesting that the targets of biologically relevant antibodies involve complex epitopes not reconstituted by the recombinant products tested. Lastly, we show that binding of MAb 6-11A to P1 on the surface of S. mutans alters P1's susceptibility to proteolytic digestion. Hence, changes in antigen processing and presentation may contribute to the immunomodulatory effects of this MAb.

Agglutinins↗
PubMed1991

Effect of nutrients on defined bacterial plaques and Streptococcus mutans C67-1 implantation in a model mouth.

Actinomyces viscosus WVU 627, Streptococcus oralis LPA-1 and Veillonella dispar OMZ 193 were cocultured on teeth in a model mouth for 66 h. Synthetic saliva containing bovine salivary glycoprotein supported bacterial growth, although the delivery of an intermittent nutrient supplement, containing 1% (w/v) glucose or sucrose, gave greater bacterial cell and viable counts. When Streptococcus mutans C67-1 was super-inoculated onto 24-hour mixed plaques, it became established under all regimens, but there was pronounced colonization resistance. With saliva only, the proportion of S. mutans at 66 h was less than 0.5% of the total cultivable microflora. When a glucose supplement was delivered for 1 h every 6 h, S. mutans attained a final proportion of 2.4%. With sucrose, both S. mutans C67-1 and its non-cariogenic glucan-deficient mutant, C67-25, attained similar proportions of 15-20%. These experiments indicate how this model can be used to study the factors influencing colonizing ability and microbial interactions in biofilms under controlled conditions.

Actinomyces↗
PubMed2002

Attenuation of glucan-binding protein C reduces the cariogenicity of Streptococcus mutans: analysis of strains isolated from human blood.

A blood isolate of Streptococcus mutans strain TW871 shows relatively low homology with MT8148, a reference oral isolate strain, and lacks the serotype-specific polysaccharide antigen, suggesting that other cell-surface structures correlate with cariogenicity. We compared cariogenicity of TW871 with MT8148 (serotype c) and blood isolate TW964 (serotype f) in rats. Strain TW871 showed significantly lower cariogenicity than MT8148 or TW964 and expressed significantly lower sucrose-independent cellular adhesion to saliva-coated hydroxyapatite and dextran-binding activity than strain MT8148. Strains TW871 and TW964 showed a defect in the gbpA gene by Southern hybridization analysis, while sequencing analysis revealed gbpC variation in TW871. These results suggest that variation in GbpC may alter cellular adherence properties and can be correlated with the cariogenicity of S. mutans in this strain.

Amino Acid Sequence↗
PubMed1999

Humoral immunity to commensal oral bacteria in human infants: salivary secretory immunoglobulin A antibodies reactive with Streptococcus mitis biovar 1, Streptococcus oralis, Streptococcus mutans, and Enterococcus faecalis during the first two years of life.

Secretory immunoglobulin A (SIgA) antibodies reactive with the pioneer oral streptococci Streptococcus mitis biovar 1 and Streptococcus oralis, the late oral colonizer Streptococcus mutans, and the pioneer enteric bacterium Enterococcus faecalis in saliva samples from 10 human infants from birth to age 2 years were analyzed. Low levels of salivary SIgA1 and SIgA2 antibodies reactive with whole cells of all four species were detected within the first month after birth, even though S. mutans and E. faecalis were not recovered from the mouths of the infants during the study period. Although there was a fivefold increase in the concentration of SIgA between birth and age 2 years, there were no differences between the concentrations of SIgA1 and SIgA2 antibodies reactive with the four species over this time period. When the concentrations of SIgA1 and SIgA2 antibodies reactive with all four species were normalized to the concentrations of SIgA1 and SIgA2 in saliva, SIgA1 and SIgA2 antibodies reactive with these bacteria showed a significant decrease from birth to 2 years of age. Adsorption of each infant's saliva with cells of one species produced a dramatic reduction of antibodies recognizing the other three species. Sequential adsorption of saliva samples removed all SIgA antibody to the bacteria, indicating that the SIgA antibodies were directed to antigens shared by all four species. The induction by the host of a limited immune response to common antigens that are likely not involved in adherence may be among the mechanisms that commensal streptococci employ to persist in the oral cavity.

Antibodies, Bacterial↗