A dextranase preparation (AD17) partially purified from a culture liquor of Spicaria violacea strain IFO 6120 significantly inhibited the formation of artificial dental plaque on a steel wire or on an extracted tooth surface. Changes in the surface morphology of Streptococcus mutans cells due to AD17 action were studied using scanning electron microscopy. S. mutans cells grown in 5% sucrose-containing broth were coated with sticky amorphous capsule-like material, whereas cells grown in sucrose in the presence of AD17 or in glucose instead of sucrose did not synthesize such capsular material. AD17 degraded commercially available dextrans of molecular weight 7 x 101 and 2 x 106 to liberate glucose and various oligosaccharides, including isomaltose. On the other hand, AD17 hydrolyzed the extracellular polysaccharides (mainly glucan in nature) of some strains of S. mutans to a limited degree. Only 15 to 36% of the total polysaccharides were hydrolyzed by AD17 with little release of isomaltose. Prolonged incubation of the polysaccharides from S. mutans with AD17 did not release additional reducing sugars, which indicates that AD17 did not contain a-1,3-glucanase activity. These results suggest that glucosidic linkages which are susceptible to AD17 may play an important role in the adherence of S. mutans cells to smooth surfaces.
Oral isolates of Streptococcus milleri were examined for their ability to coaggregate with actinomyces. Of the 68 S. mileri strains tested, including 3 reference strains, 40 strains coaggregated with Actinomyces naeslundii WVU45 (actinomyces coaggregation group B) and 36 strains coaggregated with Actinomyces viscosus T14V (actinomyces coaggregation group A). AU S. milleri strains of serotypes b (4 strains), e (2 strains), and f ( 24strains) coaggregated with both of the actinomyces. The coaggregation reactions between the S. milleri cells and A. naeslundii WVU45 cells were optimal at about pH 7.0 and were Ca2+ or Mg2+ dependent, but they were not inhibited by the presence of simple sugars or amino sugars, including lactose (up to 0.5 M). Treatment of the S. milleri cells with heat (100°C, 3 min) or proteases (trypsin, 1.0 mg/ml; pronase, 0.25 mg/ml; 37°C; 3 h) and of the actinomyces cells with periodate (0.01 M, 4°C, 16 h) destroyed their coaggregating abilities. The coaggregations between cells of the S. milleri strains, as well as cells of the Streptococcus sanguis Hi (reference strain for streptococcus coaggregation group 2) and the actinomyces strains (WVU45 and T14V), were inhibited by AFH1 (a carbohydrate receptor on T14V cells for a lectin on Hl cells). These interactions were also inhibited by anti-AFHl immunoglobulin G (IgG) and by anti-b, anti-e, and anti-f S. milleri IgG or anti-f IgG Fab fragments. These results suggest that S. milleri, at least strains of serotypes b, e, and f, belongs to streptococcus coaggregation group 2.
A highly specific aggregation factor for Streptococcus sanguis H1 (AFH1) was obtained by lysozyme treatment of Actinomyces viscosus T14V. At 1 micrograms/ml, AFH1 aggregated a suspension of S. sanguis H1, with which A. viscosus T14V coaggregates by a mechanism not inhibited by lactose: even at much higher levels AFH1 caused little or no aggregation of streptococci from other coaggregation groups (J. O. Cisar et al., Infect. Immun. 24:742-752, 1979). The most active fraction of AFH1 obtained by gel chromatography (near the void volume of Bio-Gel A1.5 m) reacted as a single antigen with anti-A. viscosus T14V serum and was unrelated to the fimbrial antigens of A. viscosus T14V. Smaller molecular fractions, at high levels, inhibited aggregation of S. sanguis H1 by high-molecular-weight AFH1 as well as coaggregation of S. sanguis H1 with A. viscosus T14V. The AFH1 fraction with high aggregating activity was composed of approximately 53% cell wall components (alanine, glutamine, lysine, N-acetylglucosamine, and N-acetylmuramic acid). 40% polysaccharide (N-acetylgalactosamine, rhamnose, and 6-deoxytalose), and 7% protein; teichoic acid was not detected. The fraction which inhibited aggregation and coaggregation contained much less of the cell wall constituents and more of the polysaccharide than the fraction with potent aggregating activity. Aggregation was completely prevented either by treating AFH1 with 0.01 M periodate at 25 degrees C for 4 h or by treating S. sanguis H1 with heat or pronase. A role for electrostatic forces in the aggregation was indicated by: (i) NaCl inhibition of aggregation, and (ii) a great decrease in aggregation potency as a result of chemical modification of either cationic or anionic groups of AFH1. On the other hand, NaCl reversed the aggregation only very weakly. The overall data suggest that a carbohydrate-protein interaction may be dominant in the aggregation of S. sanguis H1 by AFH1 and in the coaggregation of S. sanguis H1 with A. viscosus T14V.
Cell wall carbohydrate antigen of Streptococcus sanguis ATCC 10557 (serotype II/biotype B) was extracted from purified cell walls by treatment with 5% trichloroacetic acid at 4°C for 8 h. The extract was purified by chromatography on DEAE-Sephadex A-25 and Sephadex G-100 columns. The purified carbohydrate antigen produced a single precipitin band against anti-type II serum, which fused with the band produced by the autoclaved extract or the phenol-water extract of the S. sanguis cells. The type II antigen was a polysaccharide composed of glucose, galactose, rhamnose, and N-acetylgalactosamine in a molar ratio of approximately 3:6:3:2. Quantitative precipitin inhibition tests with various haptenic sugars indicated that N-acetylgalactosamine was a major determinant of the type II antigen. LITERATURE CITED 1. Appelbaum, B., and B. Rosan. 1978. Antigens of Streptococcus sanguis: purification and characterization of the b antigen. Infect. Immun. 21:896-904. INFECT. IMMUN. on July 16, 2020 by guest http://iai.asm.org/ Downloaded from s.b.e.: a streptococcus associated with subacute bacterial endocarditis.
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