DENTAL CARIES AND PERIODONTAL DISEASES

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Suppression of Candida albicans by Human Oral Streptococci in Gnotobiotic Mice

Mixed human salivary bacteria and strains of Streptococcus salivarius and S. miteor suppressed colonization of Candida albicans in gnotobiotic mice. C. albicans attached in lower numbers to epithelial cells from conventional rats than from germ-free rats, and attachment inhibition by indigenous flora may explain in part the suppression of Candida colonization

Observation of beta-hemolysis among three strains of Streptococcus mutans.

Streptococcus mutans is normally alpha- or gamma-hemolytic on blood agar plates. However, three recently isolated S. mutans strains were observed to elicit beta-hemolysis. The production and nature of a hemolytic substance were studied

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

Ability of Veillonella and Neisseria Species to Attach to Oral Surfaces and Their Proportions Present Indigenously

The present study describes the distribution of Veillonella and Neisseria species in the human oral cavity and indicates that their ability to attach to oral surfaces correlates with their proportions found in various sites of the mouth. The mean percentages of Veillonella and Neisseria of the total flora cultivable on anaerobic blood-agar plates was found to be: plaque, 0.75 and <0.13, respectively; lip, 0.38 and <0.05; cheek, 0.66 and <0.14; tongue dorsum, 9.4 and <0.12; saliva, 5.0 and <0.9. The ability of Veillonella and Neisseria species to attach to tooth surfaces was studied by cleaning the labial surfaces of incisors to render them relatively free of viable bacteria. Samples taken 1 hr later contained <0.27% Veillonella and <0.4% Neisseria, whereas saliva to which these teeth were exposed contained 20-fold higher proportions of Veillonella. These data indicate that Veillonella and Neisseria species possess a feeble ability to attach to cleaned teeth. The ability of these organisms to adhere to other oral surfaces was determined by introducing mixtures of streptomycin-resistant strains into the mouths of volunteers for 5 min. Labeled strains of Streptococcus sanguis and S. salivarius were included for comparative purposes. Analysis of samples obtained from oral surfaces after 45 min indicated that Veillonella and Neisseria adhere very poorly to preformed dental plaque as compared to S. sanguis. In contrast, Veillonella adhered to the tongue dorsum markedly better than Neisseria, S. sanguis, and S. salivarius. The greater ability of Veillonella to adhere to the tongue in relation to the other organisms studied correlates with the high proportions of Veillonella found on this site. The feeble ability of Neisseria to attach to surfaces in the oral cavity is reflected by their low proportions found on these surfaces

Morphology and Physiology of the Intracellular Development of Bacillus subtilis Bacteriophage φ25

The morphology of the intracellular development of bacteriophage φ25 in Bacillus subtilis 168M has been correlated with nucleic acid synthesis in infected cells. Host deoxyribonucleic acid (DNA) synthesis was shut off by a phage-induced enzyme within 5 min after infection, and another phage-mediated function extensively degraded host DNA at the time of cell lysis. Synthesis of phage DNA in infected cells began within 5 min and continued until late in the rise period. After phage DNA synthesis and coinciding with lysis, much of the unpackaged, newly synthesized phage DNA was degraded. Studies of thin sections of φ25 infected cells suggested that unfilled capsids may be precursors to filled capsids in the packaging process. To assess dependence of capsid formation on phage DNA replication, cells were either treated with mitomycin C and infected with normal phage or infected with ultraviolet-irradiated (99% killed) φ25. Only empty capsids were found in these cells, indicating that capsid production may be independent of the presence of newly synthesized viral DNA

Structure of Bacillus subtilis Bacteriophage φ25 and φ25 Deoxyribonucleic Acid

The structure of Bacillus subtilis bacteriophage φ25 and φ25 deoxyribonucleic acid (DNA) were studied by electron microscopy. The head of φ25 is a regular polyhedron measuring 75 nm in diameter. The uncontracted tail of φ25 is 130 nm in length and includes a large, complex tail plate. Phage φ25 DNA is double-stranded and has a molecular weight of approximately 100 million as determined by electron microscopic length measurements and analytical band sedimentation in CsCl. The complementary strands of φ25 DNA contain numerous random interruptions. Chemical analysis of φ25 DNA demonstrated that 5-hydroxymethyluracil replaces thymine and that the DNA has a mole per cent (guanine plus cytosine) of 42

Purification and characterization of an outer membrane protein adhesin from Haemophilus parainfluenzae HP-28.

Outer membranes were isolated from Haemophilus parainfluenzae HP-28 by a mild extraction method followed by Sephadex G-150 gel filtration chromatography. The first peak (pool 1) recovered contained an activity which inhibited adherence of HP-28 cells to saliva-coated spheroidal hydroxyapatite. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of pool 1 revealed a dominant protein band of 34 kDa. The SDS-PAGE-purified 34-kDa protein was excised from the gel and used for antibody preparation in rabbits. The antiserum produced was analyzed by immunoblot and was shown to be monospecific for the 34-kDa protein. Anti-34-kDa protein antibody was purified from the rabbit antiserum by protein A-Sepharose 6MB affinity chromatography. This antibody was then cross-linked to protein A-Sepharose 6MB to construct a second affinity column. The 34-kDa proteins were purified from outer membranes by this affinity chromatography. The 34-kDa protein was homogeneous, as confirmed by SDS-PAGE, isoelectric focusing, and reverse-phase chromatography analyses. Fab and Fc fragments of the purified anti-34-kDa protein antibodies were prepared by papain digestion, followed by carboxymethyl cellulose chromatography. Fab fragments from the anti-34-kDa protein antibody and the affinity-purified 34-kDa protein both showed significant inhibition of parent H. parainfluenzae HP-28 cell adherence to experimental salivary pellicle and to Streptococcus sanguis SA-1

Effect of bacterial aggregation on the adherence of oral streptococci to hydroxyapatite.

Several in vitro assay systems to measure the adherence of human dental plaque bacteria to solid surfaces such as teeth, glass, and hydroxyapatite have been published. In many studies a variety of macromolecular solutes have been used to study the adherence process. Often these solutes are able to aggregate the test bacterial and thus may alter the outcome of adherence experiments. In this study, the effects of the aggregation of Streptococcus sanguis on adherence to spheroidal hydroxyapatite is described. Adherence of preformed aggregates and of bacteria which were aggregating during the adherence reaction was examined. Bacteria were aggregated with whole saliva, concanavalin A, and wheat germ lectin. Further effects of the coaggregation of S. mitis and Actinomyces viscosus to saliva-coated spheroidal hydroxyapatite are presented. These studies suggest that formation of large aggregates resulted in a decrease in the numbers of organisms which adhered. In contrast, the formation of small aggregates actually increased the numbers of bacteria that adhered. All increases in adherent bacteria occurred at low concentrations of aggregating substance in which visible bacterial aggregation was not evident. The data indicate that adequate dose-response experiments must be performed to ensure that solutes used as probes to study adherence mechanisms do not affect the adherence simply as a result of aggregation of the test microorganisms

Clustering of an outer membrane adhesin of Haemophilus parainfluenzae.

Haemophilus parainfluenzae synthesizes an outer membrane protein adhesin which mediates binding to oral streptococci, salivary pellicle, and neuraminidase-treated erythrocytes. An indirect gold labeling technique and immunoelectron microscopy verified the location of this outer membrane protein. Further, a clustering of gold particles was observed in irregular patches at the cell surface