Burton Rosan

Dental plaque formation

Dental plaque is a complex biofilm that accumulates on the hard tissues (teeth) in the oral cavity. Although over 500 bacterial species comprise plaque, colonization follows a regimented pattern with adhesion of initial colonizers to the enamel salivary pellicle followed by secondary colonization through interbacterial adhesion. A variety of adhesins and molecular interactions underlie these adhesive interactions and contribute to plaque development and ultimately to diseases such as caries and periodontal disease.

Cloning and Expression of an Adhesin Antigen of Streptococcus sanguis G9B in Escherichia coli

A genomic library of Streptococcus sanguis, strain G9B, was constructed and expressed in Escherichia coli using a lambda gt11 expression vector. The amplified library was probed with polyclonal anti-G9B IgG and 13 antigen-positive clones were isolated. A lysate of one clone, designated PP39, absorbed the adhesion-inhibitory activity of anti-G9B IgG. This clone contained an insert of approximately 2000 bp and expressed unique 200 and 53 kDa proteins that reacted with monospecific anti-adhesin antibody. The 200 kDa protein also reacted with anti-beta-galactosidase IgG, indicating that it is a fusion protein of which 84 kDa represents the streptococcal adhesin. The 84 and 53 kDa proteins are similar in size to the major polypeptides in a streptococcal antigen complex which is associated with the adhesion of G9B to saliva-coated hydroxyapatite. The 53 kDa fragment may result from post-translational cleavage of the recombinant polypeptide.

Streptococcus sanguis: A Model in the Application in Immunochemical Analysis for the In Situ Localization of Bacteria in Dental Plaque

A review of the development of the serology of S sanguis has been presented. This species contains a group-specific antigen designated a, which appears to be a glycerol teichoic acid. It is suggested that this antigen be designated the Lancefield group H antigen. In addition, two major serotypes based on distribution of other surface antigens have been demonstrated. The grouping antiserums for S sanguis have been used to localize these bacteria in ultrastructural sections of intact dental plaque. The organisms appear antigens and seem to form pyramid-shaped microcolonies with the apex at the tooth surface and the base at the external surface of the plaque. The cells at the apex appear to have lost some surface antigens and seem to be older. The age and arrangement of the cells suggest that most plaque forms by cell division rather than by apposition of new cells from the oral cavity. If this is true, it is necessary to alter some current concepts regarding plaque development and possiby consider some different approaches to plaque control.

TOXICITY OF LACTOBACILLUS CASEI.

With the possible exception of Lactobacillus acidophilus, most of the oral lactobacilli are generally considered harmless saprophytes.1 In view of the virulence-enhancing effect of some bacterial capsules, the finding of a heavily encapsulated strain of Lactobacillus casei2 suggested the possibility of another pathogenic lactobacillus. Preliminary serologic studies showed that when whole encapsulated cells of this organism were injected into the marginal ear veins of rabbits, large, indurated, and erythematous lesions developed at the site of injection and became progressively worse. This report describes the toxic property of the organism and its role in the production of both local and systemic lesions using whole cells and several subcellular fractions.

Serology of strains of Streptococcus faecalis which produce hyaluronidase.

Sharpe and Shattock1 have indicated that the serological properties of enterococci could not be closely correlated with those physiological characteristics which are usually used to differentiate between the several species. They suggested, however, that there were two broad divisions within the enterococci in each of which the serological properties tended to correlate with the general physiological activities; one of these divisions consisted of Streptococcus faecalis and its varieties. Our investigations of strains of Str. faecalis isolated from scrapings from the teeth of humans with periodontal disease2 suggest that those strains which can depolymerize hyaluronic acid substrates by means of enzymes are directly related and distinguishable by a common antigen.

Characteristics of a protease of Streptococcus sanguis G9B which degrades the major salivary adhesin

An endogenous enzyme present in cell surface extracts of Streptococcus sanguis strain G9B degraded the major salivary adhesin of the organism. The enzyme showed optimal activity between 50 and 65 degrees C and was inactivated at higher temperatures. The activity at these unusually high temperatures seemed to be a consequence of release from the cell surface since intact whole G9B cells showed greater activity at 37 degrees C. The enzyme was not found in culture supernatants of G9B cells. The pH range for the enzyme was between 5 and 9. It was inhibited by iodoacetic acid, Hg2+, Cu2+, EDTA, SDS, and PMSF, but not by TLCK, TPCK, soybean trypsin inhibitor, cysteine, dithiothreitol, leupeptin, Ca2+, Mg2+ or saliva. The enzyme did not show any activity against human or rabbit IgG or human IgA. Enzyme activity was also found in S. sanguis strains Adh- (a spontaneously occurring non-adherent mutant of G9B), and M-5.

A Comparison of the Phenol Water and Rantz and Randall Teichoic Acid Antigens in Group H Streptococci

The Group H antigen which is found in most strains of Streptococcus sanguis is usually extracted by the Rantz and Randall (RR) autoclave method (1). Previous studies had suggested that this antigen was a glycerol teichoic acid (2). Although the RR extracts of a variety of streptococcal Lancefield groups indicated the specificity of the Group H antigen (3), a reaction of identity was obtained when phenol water (PW) preparations of Group D streptococci were tested against Group H antisera (1); Group D antisera did not show this cross reaction with either PW or RR extracts of Group H organisms. These results suggested that the RR and PW extractions affected the cells differently. Both of these methods are important starting points in many procedures for antigen purification and for serological identification. Although the PW method is known to disrupt both covalent and non-covalent bonds (4), the effect of the RR extraction on cells is still the subject of much debate. Moreover, though PW extracts are known to solubilize membrane associated lipoteichoic acids (LTA), the effects on other cell surface components are not known (5–8). The structures affected by the RR procedure have still not been identified.

Identification of a Streptococcus sanguis Receptor for Salivary Agglutinins

The objective of this study was to characterize a fraction from oral streptococci containing receptor activity for salivary agglutinin molecules. Several species and strains of streptococci were disrupted in a Ribi press. The supernatant was nuclease-treated and subjected to differential centrifugation. Receptor activity in the fractions was measured by the inhibition of saliva-mediated bacterial aggregation. In addition, bacterial strains were tested for their ability to aggregate and to deplete saliva of agglutinin activity. Three patterns of activity were observed: Streptococcus sanguis M5 depleted saliva of agglutinin activity and aggregated well; Streptococcus sanguis CC5A depleted saliva of agglutinin but did not aggregate well; and Streptococcus faecalis S-161 neither depleted saliva of agglutinin nor did it aggregate. The 105,000 g supernatant fractions derived from Ribi-disrupted Streptococcus sanguis M5 and CC5A, but not from Streptococcus faecalis, showed dose-dependent inhibition of saliva-mediated aggregation. This inhibitory activity was non-dialyzable, had the same heat and trypsin sensitivity as that seen with intact bacteria, and was not due to enzymatic digestion of the salivary agglutinin. Iso-electric focusing revealed a single active region with a pI of 5.5 which was clearly separated from the bulk of the bacterial proteins.