Effect of whole saliva on the rheologic behavior of extracellular water-soluble glucan produced by Streptococcus mutans

Abstract— The viscosity of mixtures of Streptococcus mutans water-soluble glucan and stimulated whole saliva or buffer was measured at pH 5, 6, 7, and 8. The viscosity was measured as a function of shear rate in the range 15 s^-1-230 s^-1. Though the centrifuged saliva had a viscosity close to that of water it increased the viscosity of the glucan up to 65% at pH 6 and 55% at pH 7 and at a shear rate of 20 s^-1, indicating an interaction between saliva components and glucan that could be an important part of the cohesive forces of plaque matrix. The interaction between saliva and glucan was less pronounced at pH 5 and 8, which indicates a charge-dependent interaction. The viscosity increase at pH 6 and 7 was higher at low than at high shear rates, suggesting a higher contribution to plaque stability when weak as opposed to high mechanical forces are exerted on the plaque.     

Effect of delmopinol on the viscosity of extracellular glucans produced by Streptococcus mutans.

The surfactant delmopinol, which is a new antiplaque agent with a low anti-microbial profile, was tested for its effects on the viscosity of bacterial extracellular glucans. Glucans were isolated from Streptococcus mutans broth supernatants incubated with 0.15 M sucrose in 50 mM sodium phosphate buffer at pH 6. The viscosity was measured in a shear rate range from 15 to 230 reciprocal seconds. The viscosity of the water-soluble glucan was found to be independent of shear rate whereas the water-insoluble glucan showed a strong shear thinning. The addition of delmopinol to preformed glucans did not affect the viscosity nor the shear rate dependence of the glucans. However, when present during synthesis of the polysaccharides, delmopinol was found to reduce the viscosity of both water-soluble and water-insoluble glucans by approximately 50% at the shear rates investigated. The reduction in viscosity for the water-soluble glucans was obtained at a delmopinol concentration of 0.32 mM (0.01%) and for the water-insoluble glucans at 3.2 mM delmopinol. The observed reduction of viscosity of glucans indicates that the in vivo stability of plaque matrix after delmopinol treatment would be lowered, which may lead to a reduction of plaque cohesion and thus facilitate mechanical plaque removal.     

Methylation analysis of extracellular glucans produced by Streptococcus mutans strain JC 2.

The fine structure of the soluble (SG) and the major insoluble (IG-1) glucans produced by Streptococcus mutans strain JC 2 cultured in sucrose medium was investigated by methylation analysis. These glucans are highly branched at the C-3 and C-6 positions of the d-glucopyranose residues, and each glucan contains α-1:3 and α-1:6 glucopyranosyl linkages in different proportions. The SG contained 10 per cent α-1,3,6 linked branching residues, 10 per cent non-reducing terminal residues, 47 per cent α-1:6 linked units and 33 per cent α-1:3 linked units. The IG-1 contained 9 per cent α-1,3,6 linked branches, 9 per cent terminals, 36 per cent α-1:6 linked units and 46 per cent α-1:3 linked units.     

变形链球菌Ⅰ型和Ⅲ型合成葡聚糖的研究

目的 通过对Ⅰ型ＪＢＰ（ｃ型）和Ⅲ型６７１５（ｇ型）变链菌在不同状态葡糖基转移酶（ＧＴＦ）所合成的水不溶性和葡聚糖（ＩＧ）和水溶性葡聚糖（ＳＧ）的测定来研究两种变链菌的ＧＴＦ－Ⅰ和ＧＴＦ－Ｓ是否存在差异。方法 制备ＪＢＰ和６７１５的含酶上清液（ｃｅｌｌ－ｆｒｅｅ ｅｎｚｙｍｅ）及含酶提取液（ｃｅｌｌ－ｂｏｕｎｄ ｅｎｚｙｍｅ），以蔗糖为底物，恒温培养后分别收集ＩＧ和ＳＧ。     

Effects of exogenous insoluble glucan primer on insoluble glucan synthesis by Streptococcus mutans

The effects of exogenous glucans on WIG synthesis by S. mutans were investigated by turbidimetric measurement. The rapid synthesis of WIG by an enzyme preparation from PS-14 culture fluid proceeded after a lag period of several min. The addition of exogenous WIG, which was previously prepared using the PS-14 enzyme, caused a marked reduction of the lag period with little change in the reaction rate. The length of lag period was affected by the concentrations of WIG primer, enzyme and salts, and the reaction pH. The WIGs from other strains and the periodate-treated WIGs also exhibited effects similar to the PS-14 glucan. In contrast, dextran, starch, dextrin, laminarin, cellulose, chitin, and inulin were without any effect. These results suggest that such lag-reducing effect is specific to glucans containing a significant amount of alpha-(1 leads to 3) linkages.     

白屈菜红碱对变形链球菌葡糖基转移酶和细胞外水不溶性多糖的影响

目的：研究白屈菜红碱对变形链球菌葡糖基转移酶和细胞外水不溶性多糖合成的影响。方法：采用二倍稀释法,用含2％蔗糖的脑心浸萃液肉汤琼脂（BHI）液体培养基,将白屈菜红碱稀释为从390．6μg／ml到24．4μg／ml共计5个浓度的溶液．以BHI液体培养基作为阴性对照组。加入变形链球菌菌液,厌氧培养24h后,将培养物离心,收集上清液．分为2份。一份提取葡糖基转移酶,采用考马斯亮蓝法和Somogyi法分别测定总蛋白和还原糖含量,计算酶活性和比活力大小;另一份上清液采用蒽酮法测定水不溶性多糖的含量。实验结果采用SPSS13．0软件包进行数据处理,总体均数之间的比较采用单因素方差分析,采用Pearson相关检验进行两组样本之间的相关分析。结果：随着白屈菜红碱溶液浓度的升高,葡糖基转移酶活性和水不溶性多糖含量逐渐降低,各组总体均数间均具有高度显著性差异（P〈0．01）,葡糖基转移酶各实验组与对照组酶活性及比活力之间均有高度显著性差异（P〈0．01）;除24．4μg／ml浓度组外．各实验组与对照组水不溶性多糖含量也均有高度显著性差异（P〈0．01）。葡糖基转移酶活性和水不溶性多糖含量之间呈正相关关系（r=0．883．P〈0．01）。结论：白屈菜红碱对变形链球菌葡糖基转移酶和细胞外水不溶性多糖的合成具有显著抑制作用。     

Acid diffusion through extracellular polysaccharides produced by various mutants of Streptococcus mutans

Mutants of Streptococcus mutans V403, constructed by allelic exchange and altered in their capacity to produce enzymes involved in the production of extracellular polysaccharides from sucrose, were used to study the role of glucans and fructans in the diffusion of ions through cell concentrates. A 4.0mm diameter, 0.75 mm deep diffusion chamber with an ion-sensitive field-effect transistor electrode positioned at the base was used to monitor the diffusion of hydronium ions from a sodium lactate buffer using cell concentrates prepared from bacteria grown in various concentrations of sucrose and glucose. The wild-type strain V403 produced at least seven times as much water-insoluble glucan (ISG) from sucrose as mutants deficient in various combinations of glucosyltransferase B (GTF B), GTF C, GTF D and fructosyltransferase. The fastest diffusion of hydronium ions occurred with sucrose-grown cell concentrates of strain V403, and the time of diffusion to the bottom of the chamber was approximately 2.3 times longer when this strain was grown in glucose. The speed of diffusion with glucose-grown V403 was similar to that obtained with each of the mutants. When cells of strain V403 grown in sucrose and glucose were mixed, increases in diffusion speed were found to be directly related to the proportion of sucrose-grown cells. The mixing of ISG with several strains of S. mutans revealed that increases in diffusion speed were directly related to the quantity of ISG added.     

Effect of a chlorhexidine varnish on Streptococcus mutans in saliva

The aim of the present work was to evaluate the effect of a thymol/chlorhexidine varnish at 1% on Streptococcus mutans (S. mutans) in saliva applied after teaching and evaluating an oral hygiene technique and dressing the cavities to reduce the bacterial load. Streptococcus mutans levels in saliva samples and dental status were evaluated in 38 girls between 6 and 13 years of age with high risk of caries. The girls were then trained and assessed in oral hygiene. On day seven, oral hygiene assessment was repeated and supragingival plaque control was performed. After 15 days (day 21) another culture was performed and the level of S. mutans in saliva samples was determined. Evaluation and reinforcement of the oral hygiene technique were repeated and the cavities were dressed to reduce the bacterial load. At 36 days from the onset of the experiment, culture S. mutans counts were performed; evaluation and reinforcement of the oral hygiene technique were undertaken and the girls were divided randomly into two groups: 1 The teeth of the experimental group were painted with a varnish containing 1% chlorhexidine and thymol. 2 The teeth of the control group were painted with a placebo varnish containing only thymol. After a further 15 days (day 51), another culture and S. mutans counts were performed. The results showed a gradual reduction in the S. mutans counts in saliva in each subsequent experimental period analyzed. Significant differences between the experimental group and the control group were recorded after treatment. It can be concluded that the levels of S. mutans decreased in each subsequent experimental period and that the application of a 1% chlorhexidine varnish elicited a significant reduction in S. mutans levels.     

Viability of Streptococcus mutans and Streptococcus sobrinus in whole saliva with varying concentrations of indigenous antimicrobial agents.

We have studied the possible relationship between indigenous salivary antimicrobial agents, indigenous mutans streptococci and the capability of added mutans streptococci to grow in saliva. Stimulated whole saliva was collected from 19 healthy donors. Saliva samples were sterilized, supplemented with glucose and inoculated with Streptococcus mutans or Streptococcus sobrinus. The mixtures were incubated for 20 h followed by counting of viable cells. Saliva samples were analysed, both before and after sterilization, for indigenous antimicrobial agents and the bacterial flora. The subjects could be divided into two groups: those (n = 9) whose saliva promoted and those (n = 10) whose saliva inhibited the growth of the inoculated streptococci. A statistically significant correlation (+0.82, p < 0.001) was found between the numbers of viable cells of S. mutans and S. sobrinus after incubation in saliva. The sterilization procedure reduced the content of all antimicrobial proteins. Salivary antimicrobial factors, or levels of indigenous mutans streptococci, did not differ between the two groups. We conclude that none of the individual salivary antimicrobial factors alone can explain the large individual differences in growth-promoting or growth-inhibiting patterns of saliva on S. mutans and S. sobrinus. Inter-individually, saliva either supports or inhibits the growth of mutans streptococci, indicating a similar response of these two species in relation to the properties of saliva.     

Structure of extracellular water-soluble polysaccharides synthesized from sucrose by oral strains of Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguis and Actinomyces viscosus.

Extracellular water-soluble polysaccharides produced from sucrose by various strains of oral streptococci and one strain of Actinomyces viscosus were isolated and analysed. Methylation analysis and characterization of the cleavage products by gas-liquid chromatogra-phy-mass spectrometry were the principal methods used. Streptococcus salivarius ATCC 9759, ATCC 13419 and NCTC 8618 and A. viscosus ATCC 15987 synthesized fructans of the levan-type with (2 → 6)-linked β-fructofuranoside residues, branched in the 1-position (15–17 per cent) and of high molecular weight (2.7 × 10⁶ ? 21.6 × 10⁶). Strep. mutans strain JC2, however, produced a fructan, 12.4 × 10⁶, of the inulin-type with (1 → 2)-linked β-fructofuranoside residues and with some branching in the 6-position (6 per cent). All glucans isolated from Strep. mutans strains JC2, FA1 and Ingbritt and Strep. sanguis strain 903 were of the dextran-type, predominantly (1 → 6)-linked, or to a lesser extent (1 → 3)-linked (9–12 per cent) with branching in the 3- and 6-position (19–23 per cent). Both high (12.4 × 10⁶) and low molecular weight glucans (129,000–136,000) were found.     

Effect of a fluoride-containing varnish on Streptococcus mutans in plaque and saliva

Abstract – The effect of topical application of a fluoride-containing varnish, Duraphat®, on the level of Streptococcus mutans in saliva and in dental plaque was investigated in schoolchildren. Samples of saliva and pooled buccal plaque were taken before varnish application and 4, 10 and 21 d after treatment. Fluoride varnish treatment with or without a preceding dental prophylaxis had no significant effect on the plaque and salivary levels of S. mutans. The findings suggest that the caries-reducing effect of fluoride varnish cannot be explained by an alteration of the incidence of 5. mutans in dental plaque or in saliva.     

Effect ofintensive treatmetn with chlorhexidine on number of Streptococcus mutans in saliva

Abstract – The effect of intensive treatment with chlorhexidine on the number of S. Mutans in saliva was studied in 24 schoolchildren highly infected with this organism. Chlorhexidine gel in individula dental trays was applied under supervision on two concecutive days, four times the first day an dthree times the second day. The number of S.mutans in saliva was monitored for 6 months. Immediately after treatment, the number was rreatlyreduced in all of the children. Thirty days after treatment only three children had more than 2×10⁵ S.mutansmi saliva, and after 4 months, 11 children still had less than 2×10⁵ S.Mutans/ml saliva. After 6 months the effect of the treatmetn was obvisous in 20% of the children. The results indicate that intensive treatment with chlorhexidine can be used to reduce the S.mutans infection. The antimicrobial treatment, however, should be individully controlled because of variations in the response of the subjects.     

Effect of intensive treatment with chlorhexidine on number of Streptococcus mutans in saliva

The effect of intensive treatment with chlorhexidine on the number of S. mutans in saliva was studied in 24 schoolchildren highly infected with this organism. Chlorhexidine gel in individual dental trays was applied under supervision on two consecutive days, four times the first day and three times the second day. The number of S. mutans in saliva was monitored for 6 months. Immediately after treatment, the number was greatly reduced in all of the children. Thirty days after treatment only three children had more than 2 X 10(5) S. mutans/ml saliva, and after 4 months, 11 children still had less than 2 X 10(5) S. mutans/ml saliva. After 6 months the effect of the treatment was obvious in 20% of the children. The results indicate that intensive treatment with chlorhexidine can be used to reduce the S. mutans infection. The antimicrobial treatment, however, should be individually controlled because of variations in the response of the subjects.     

Effect of orthodontic treatment on prevalence of Streptococcus mutans in plaque and saliva

The effect of orthodontic treatment on the prevalence of Streptococcus mutans was investigated in 14 subjects. Insertion of appliances tended to give a transient decrease in S.mutans levels, in both plaque and saliva, possibly due to elimination of S.mutans reservoirs by the banding procedure. After 3 months of extensive banding, the S.mutans proportions surpassed pretreatment levels in saliva and on banded teeth, whereas unbanded surfaces only showed a slight increase. It was thus concluded that creation of new retentive areas favors the local growth of S.mutans, which in turn increases the general infection level of this organism. Time was, however, needed before elevated levels were reached. Insertion of appliances tended to eliminate the characteristic gradient of S.mutans levels within the dental arches.