Streptococcus sanguis: a model in the application in immunochemical analysis for the in situ localization of bacteria in dental plaque

Actinomyces naeslundii in initial dental biofilm formation

The combined use of confocal laser scanning microscopy (CLSM) and fluorescent in situ hybridization (FISH) offers new opportunities for analysis of the spatial relationships and temporal changes of specific members of the microbiota of intact dental biofilms. The purpose of this study was to analyse the patterns of colonization and population dynamics of Actinomyces naeslundii compared to streptococci and other bacteria during the initial 48 h of biofilm formation in the oral cavity. Biofilms developed on standardized glass slabs mounted in intra-oral appliances worn by ten individuals for 6, 12, 24 and 48 h. The biofilms were subsequently labelled with probes against A. naeslundii (ACT476), streptococci (STR405) or all bacteria (EUB338), and were analysed by CLSM. Labelled bacteria were quantified by stereological tools. The results showed a notable increase in the number of streptococci and A. naeslundii over time, with a tendency towards a slower growth rate for A. naeslundii compared with streptococci. A. naeslundii was located mainly in the inner part of the multilayered biofilm, indicating that it is one of the species that attaches directly to the acquired pellicle. The participation of A. naeslundii in the initial stages of dental biofilm formation may have important ecological consequences.

Growth, development, and gene expression in a persistent Streptococcus gordonii biofilm

A model for the protracted (30-day) colonization of smooth surfaces by Streptococcus gordonii that incorporates the nutrient flux that occurs in the oral cavity was developed. This model was used to characterize the biphasic expansion of the adherent bacterial population, which corresponded with the emergence of higher-order architectures characteristic of biofilms. Biofilm formation by S. gordonii was observed to be influenced by the presence of simple sugars including sucrose, glucose, and fructose. Real-time PCR was used to quantify changes in expression of S. gordonii genes known or thought to be involved in biofilm formation. Morphological changes were accompanied by a significant shift in gene expression patterns. The majority of S. gordonii genes examined were observed to be downregulated in the biofilm phase. Genes found to be upregulated in the biofilm state were observed to encode products related to environmental sensing and signaling.

Corncob formation between Fusobacterium nucleatum and Streptococcus sanguis

Corncob formation in dental plaque was believed to be limited to strains of Bacterionema matruchotii and Streptococcus sanguis. We observed recently that strains of Fusobacterium nucleatum also interacted with S. sanguis to form corncobs. Since the fusobacteria are among the first anaerobic filaments to colonize subgingival plaque, these interactions could serve as a connecting link between the transformation of supra- to subgingival plaque. To further characterize these interactions, quantitative in vitro studies of the kinetics of corncob formation of the fusobacteria were undertaken. These studies indicated that fewer streptococci were needed to saturate F. nucleatum strain 364 compared to strain 10953. Corncob formation with both strains was enhanced with increasing pH up to pH 8, at which point autoaggregation of the streptococci occurred. Variation in ionic strength and divalent cations had little effect on the interaction, and EDTA suppressed aggregate formation only slightly. Detergents at concentrations above 0.05% also inhibited corncob formation. Electron micrographs suggested that attachment of the cocci to the fusiforms was mediated through localized tufts of fimbriae, as they are in the Bacterionema system. However, although both trypsin and heat treatment of the streptococci inhibited corncob formation with fusobacteria, the effects were not as complete as those seen in Bacterionema species. Unlike the Bacterionema model, trypsin and heat treatment of the fusobacteria resulted in inhibition of corncob formation. These results suggest that several different receptors may be involved in corncob formation.

Purification and immunochemical characterization of Streptococcus sanguis serotype I carbohydrate antigen

The serotype-specific antigen of Streptococcus sanguis ST3 (serotype I, biotype A) was extracted, chromatographically purified, and characterized by immunological and chemical methods. The antigen was extracted from purified cell walls with hot trichloroacetic acid, followed by ion-exchange chromatography on a DEAE-Sephadex A-25 column and gel filtration through a Sephadex G-100 column. A peak fraction was obtained that gave a single precipitin band when reacted with anti-type I serum. The type I antigen was a polysaccharide composed of glucose, rhamnose, and N-acetylglucosamine in a molar ratio of 1.4:2.5:1.0. Quantitative precipitin inhibition tests with various haptenic sugars indicated that an alpha-glucosidic linkage is the immunodeterminant of the type I antigen.

Immunochemical comparison of cell-wall antigens of various viridans streptococci, including strain 2A2+3 hot from recurrent oral aphthous ulceration in man

Several studies suggest that patients with recurrent aphthous ulceration show cell-mediated and humoral immunity to antigens of Streptococcus sanguis, particularly strain 2A2+3 HOT which is said to be antigenically similar or identical to Strep. sanguis strain ATCC 10556. However, physiological classification as well as analysis of the immunologically dominant cell-wall antigens by immunoelectrophoresis and indirect immunofluorescence showed that the strain is actually a strain of Streptococcus mitis and is antigenically more like ATCC 10557 than ATCC 10556. The findings illustrate the antigenic heterogeneity of the Strep. sanguis and Strep. mitis taxons, and demonstrate the need for antigenic analysis of viridans streptococcal strains used in immunological studies of the aetiology of disease and in antiserum production. Commercial streptococcal group and antisera were also tested.

Isolation of a protein-containing cell surface component from Streptococcus sanguis which affects its adherence to saliva-coated hydroxyapatite

The isolation and partial characterization of a protein-containing cell surface component from Streptococcus sanguis which blocks the adherence of this microbe to saliva-coated hydroxyapatite are described. Several methods of extraction were attempted. Sonication of whole cells and cell walls proved to be the most successful and yielded biologically active adherence-blocking components. The adherence-blocking ability of these components was effective in intraspecies blocking experiments. The extract obtained from cell walls of S. sanguis was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and shown to contain one major and two to three minor bands when stained with Coomassie blue. The molecular weight of the major band was estimated to be 70,000 to 90,000. Gel filtration of the sonified cell wall extract on 10% agarose yielded two active adherence-blocking peaks, the void volume and a second peak.

Isolation and immunobiological classification of Streptococcus sanguis from human tooth surfaces

A total of 113 pure cultures of Streptococcus sanguis were obtained from dental plaque samples of 64 subjects. All isolates synthesized glucan from sucrose, elaborated peroxide, and were alpha-hemolytic. Two biotypes and four serotypes were differentiated within the species. Biotype A (95 isolates) fermented salicin and inulin and hydrolyzed arginine and esculin, whereas biotype B (18 isolates) did not possess these activities. The isolates were serotyped with autoclaved extracts against whole-cell antiserum to strains ATCC 10556 or ST3 (serotype I), ATCC 10557 (serotype II), ATCC 10558 (serotype III), and ST7 (serotype IV), by the capillary precipitin test. Serotypes I, II, III, and IV were found to consist of 24, 16, 37, and 15 isolates. Type IV was demonstrated anew in this study. The remaining 21 isolates were not typed because of either multiple reactions or nonreactivity against the standardized typing sera. All isolates of serotype II belonged to biotype B, which resembles Streptococcus mitior physiologically. Five isolates representing four serotypes and an untypable strain were examined for their cariogenicity against specific-pathogen-free Sprague-Dawley rats fed high sucrose diet no. 2000. Organisms of each isolate were established in the mouths of the rats, but only three isolates induced weak caries that were restricted to pits and fissures of occlusal surfaces of the teeth.

Biology, immunology, and cariogenicity of Streptococcus mutans

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Characterization of tufted streptococci isolated from the "corn cob" configuration of human dental plaque

Streptococci isolated from "corn cob" configurations of human dental plaque possess a polar fibrillar tuft extending 100 to 150 nm from one pole of the cell. The two strains studied were physiologically related to the Streptococcus sanguis-Streptococcus mitior group and were most similar to Streptococcus mitis ATCC 903. The corn cob streptococci were serologically related to S. sanguis serotype 1. The polar tuft contained at least two antigenically distinct components, one serologically related to the glycerol phosphate backbone of teichoic acid. The other was an electrophoretically slow-moving antigen similar to a component of S. mitis ATCC 903. It is suggested that the corn cob streptococci in vivo adhere to Bacterionema matruchotii by means of the polar tuft.

Modification of human parotid saliva proteins by oral streptococcus sanguis

Polyacrylamide gel electrophoresis was used to analyze the effect of Streptococcus sanguis on the anionic proteins in human parotid gland saliva. Cell-free culture supernatants and washed-cell preparations from 23 strains of S. sanguis caused marked modification of various salivary proteins. Control studies showed that the alterations in protein profiles by the bacteria were not due to attachment of protein to the cells. Protease inhibitors were used to confirm that proteolysis by distinct enzymatic activities was responsible for most of the modifications. There was no discernible relationship between the degradation patterns and the various immunologic or genetic groups of S. sanguis. Proteins which contained high concentrations of proline were extensively degraded by S. sanguis. This effect could be blocked with the protease inhibitor phenylmethyl-sulphonyl fluoride.

Antigens of Streptococcus sanguis: purification and characterization of the b antigen

The antigen defining Streptococcus sanguis serotype 2 has been designated the b antigen. This antigen can be detected in extracts, obtained from whole cells by autoclaving (Rantz and Randall extraction), as a single precipitin band using a reference antiserum (M-5). However, the extract can also be shown to contain a teichoic acid using anti-polyglycerol phosphate serum. This teichoic acid does not contain the antigenic determinant for group H specificity. Studies of the b antigen have been hampered because of the difficulty in separating the b antigen from the teichoic acid using ion-exchange and molecular sieve chromatography. However, a relatively pure preparation has been obtained by affinity chromatography using anti-polyglycerol phosphate serum coupled to Sepharose. The isolated b antigen is a typical streptococcal cell wall polysaccharide composed of glucose, rhamnose, and N-acetylglucosamine in a molar ratio of 2.5:1.0:0.1. The antigen appears to have a single antigenic determinant closely related to isomaltose (glucose alpha-1,6-glucoside) based upon hapten inhibition studies.

Relationship of the cell wall composition of group H streptococci and Streptococcus sanguis to their serological properties

Previous studies indicated the a antigen was widely distributed among strains of Streptococcus sanguis and the group H streptococci. The cell walls of strains containing this antigen had moderate to large quantities of rhamnose, small amounts of phosphorus, and little to no ribitol. The molar ratios of the peptidoglycan amino acids and hexosamines suggested a di-alanyl cross bridge. The homogeneity of the walls of these strains suggested that serological group H can be considered synonymous with S. sanguis. In contrast those strains that did not contain the a antigen had only small amounts of rhamnose in their cell walls, galactosamine and ribitol were always detected, and large quantitites of phosphorus were present. The molar ratios of peptidoglycan components in the latter strains suggested a direct alanyl-lysl cross bridge. Although many of these strains had been classified either as S. sanguis or group H streptococci because of minor serological cross-reactions and similar biochemical properties, the distinct differences between the composition of their cell walls and those of S. sanguis and group H streptococci indicate that they do not belong in this species or group. The cell walls of strains containing the a antigen are relatively homogeneous and therefore it is suggested that cells containing this antigen be considered Lancefield serological group H.