Ronald J. Gibbons

Inhibition of Bacterial Adherence by Secretory Immunoglobulin A: A Mechanism of Antigen Disposal

Preparations of secretory iminunoglobuilin A (S-IgA) isolated from human parotid fluid specifically inhibited the adherence of Streptococcus strains to epithelial cells. Since bacterial adherence is a prerequisite for colonization of mucous surfaces. S-IgA-mediated inhibition of adherence would limit bacterial colonization. This mechanism can explain how secretory immunoglobulins function in the disposal of bacterial antigens.

The microbiota of the gingival crevice area of man—II: The predominant cultivable organisms

Abstract All of the cultivable organisms present in high dilutions of debris from the gingival crevice area of man have been isolated, partially characterized, and their relative proportions ascertained. No significant quantitative or qualitative differences were observed in the microbiota of normal and periodontally-involved individuals. The gingival crevice microbiota was found to be comprised as follows: 28.8 per cent gram positive facultative cocci; 20.2 per cent gram positive anaerobic rods; 16.1 per cent gram negative anaerobic rods; 15.3 per cent gram positive facultative rods; 10.7 per cent gram negative anaerobic cocci; 7.4 per cent gram positive anaerobic cocci; 1.2 per cent gram negative facultative rods; and 0.4 per cent gram negative facultative cocci. Anaerobes comprised 54.3 per cent, gram positive organisms 71.5 per cent, and bacillary forms 52.8 per cent of the cultivable organisms.

THE SOURCE OF SALIVARY BACTERIA.

IT IS WELL KNOWN that saliva contains large numbers of bacteria. These organisms have been thought to be dislodged from dental plaque or from gingival debris through the washing action of saliva. Consequently saliva has often been utilized as a substitute for dental plaque or gingival crevice debris in studies designed to elucidate the role of bacteria in either dental caries or periodontal disease. However, KRASSE (1954a) studied the distribution of Streptococcus salivarius in plaque, saliva, and on the tongue and cheeks. He found that Streptococcus salivarius comprised a large proportion of the facultative streptococci present in saliva and on the tongue, but this organism comprised only a small percentage of the facultative streptococci present in dental plaque. As a result of these and other studies, KRAUSE (1953,1954a,b)

Suppression of Streptococcus mutans in the Mouths of Humans by a Dental Prophylaxis and Topically-applied Iodine

A prophylaxis followed by three topical applications of an iodine-potassium iodide solution significantly reduced the levels of Streptococcus mutans in fissure and approximal plaques and in saliva. Reductions persisted 20-24 weeks after treatment in salivary and approximal samples. A prophylaxis alone exerted a small and temporary reduction of S. mutans in occlusal fissure plaque, but did not reduce the levels of this organism in approximal plaque or in saliva. A significant relationship existed between the levels of S. mutans in saliva and the proportions of this organism in plaque. The dorsum of the tongue does not appear to constitute a significant reservoir for S. mutans following disinfecting procedures.

Vitamin K Compounds in Bacteria That Are Obligate Anaerobes

A naphthoquinone-dependent strain of Bacteroides melaninogenicus has been used in a microbiological assay to survey bacteria for compounds of the vitamin K group. Organisms known to contain vitamin K, as well as several bacteria that are obligate anaerobes, produced substances which satisfied the naphthoquinone requirement of the assay organism. Vitamin K was chemically isolated from strains of Bacteroides melaninogenicus, Bacteroides fragilis, and Veillonella alcalescens.

Lysozyme Insensitivity of Bacteria Indigenous to the Oral Cavity of Man

SYNOPSIS IN INTERLINGUA INSENSIBILITATE A LYSOZYMA DEL PARTE DE BACTERIOS INDIGENE AL CAVITATE ORAL DEL HOMINE.-Esseva constatate que inter 112 culturas pur, representante 13 gruppos de bacterios oral, nulle esseva lysate per lysozyma a concentrationes de 5,50, o 500 μg per ml, secundo essayos turbidimetric. In plus, esseva trovate que le plus numerose bacterios cultivabile ab specimens de debris gingival, de placa dental, e de saliva cresceva in le presentia de 0,5, 5, o 50 μg per ml de lysozyma. Quando specimens de debris gingival esseva incubate con 50 μg per ml de lysozyma, nulle liberation de proteina solubile esseva detegite. Iste datos pare indicar que lysozyma per se exerce pauc effecto super bacterios indigene al cavitate oral del homine.

Use of Percoll Density Gradients for Studying the Attachment of Bacteria to Oral Epithelial Cells

An assay for studying the attachment of bacteria to oral epithelial cells has been developed which utilizes Percoll density gradient centrifugation to separate bacteria and epithelial cells. 3H-thymidinelabeled bacteria were incubated with suspensions of buccal epithelial cells in microtitration plates for 2.5 hr at 35°C. The mixtures were then subjected to density gradient centrifugation in 50% Percoll. Epithelial cells with attached bacteria formed a band near the top of the tube, while unattached bacteria formed a band near the bottom. The epithelial cells were collected on membrane filters, and the number of attached bacteria was determined by scintillation counting. Binding of S. mitis C5 was found to increase with time, and equilibrium was attained within two hr. Saturation of available binding sites occurred when 107 S. mitis cells were incubated with 1.5 × 104 buccal epithelial cells. The numbers of streptococci which attached as determined with this assay were in good agreement with values obtained by direct microscopic counts. Adsorption of S. mitis C5 cells was adequately described by a Langmuir isotherm (correlation coefficient 0. 998). This permitted calculation of estimates of the number of binding sites and the affinity of the organism. The assay proved reliable even when as few as 1000 epithelial cells were used. Treating the epithelial cells with neuraminidase or trypsin significantly decreased the number of S. mitis C5 cells which attached. In contrast, binding of A. naeslundii 12104 to neuraminidase-treated cells was increased, and attachment of B. gingivalis 381 was also enhanced, especially to epithelial cells which had been treated with trypsin.

Multiple ankylosis occurring in rat teeth

Abstract The occurrence of multiple ankylosis in a litter of Sprague-Dawley gnotobiotic rats has been reported. Literature pertinent to the anomaly has been reviewed with respect to the possible cause of ankylosis. The probability of the implication of genetic factors in the etiology of the present condition is suggested.

Role of Extracellular Bacterial Polysaccharides in the Caries Process

It is now clear that specific bacteria are essential for the initiation of smooth surface carious lesions and periodontal disease in experimental animals. These observations have focused attention on gelatinous dental plaques as a prerequisite for the initiation of both pathologic processes. Animals infected with organisms capable of eliciting these diseases develop massive accumulations of gelatinous plaque, whereas animals harboring ineffective bacteria do not. Thus, the pathogenicity of these organisms is intimately associated with their ability to induce plaque formation. The initiation of carious lesions in pits and fissures of teeth shows a lower degree of bacterial specificity. As these sites provide protected regions for food impaction and bacterial proliferation, pit and fissure carious lesions are less dependent on gelatinous plaque. Currently, there are two types of bacteria recognized as being able to induce gelatinous plaques. Specific streptococci that elicit plaque formation and caries when inoculated into the mouths of experimental animals have been isolated from rodents and man. In addition, certain diphtheroidal organisms, Odontomyces viscosus, are associated with gingival plaque, root caries, and periodontal disease in rodents. Recently, it has become clear that the production of certain extracellular polymers, particularly insoluble adhesive polysaccharides of the dextran and levan type, plays a vital role in the formation of the streptococcal plaques. Investigators in Sweden, Switzerland, England, and the United States have observed that some streptococci synthesize gelatinous polysaccharides of the dextran and levan type from sucrose, but not from other sugars commonly found in the mouth. The formation of these polymers affects the adhesive characteristics of the streptococci, because these organisms form gelatinous plaque-like deposits specifically in sucrose

Award for Research in Oral Science

1230 both rodents and man have been found to synthesize large quantities of extracellular polysaccharides when provided with sucrose, whereas noncariogenic streptococci synthesize little or none. Cultures of cariogenic organisms grown in sucrose broth reflect polysaccharide synthesis for the or,anisms adhere to the walls of culture vessels forming gelatinous masses. This suggests that the production of these gelatinous polymers could enable cariogenic bacteria to form plaque. The extracellular polysaccharide formed by most cariogenic streptococci is a dextranlike polymer for it is composed almost entirely of glucose. Solutions of the polysaccharide react with antidextran antiserum, and the polymer is hydrolyzed by preparations of dextranase. Dextran has been found to have a number of characteristics which are of possible importance for the initiation of dental plaque. First, it is able to adhere to untreated or saliva-coated powdered hydroxyapatite; secondly, it forms a precipitate with saliva; thirdly, it is relatively resistant to attack by plaque bacteria. Samples of pooled human plaque have been found to contain a constituent which is antigenically identical to dextran, indicating that at least part of the matrix of plaque is composed of a polysaccharide which appears identical to the extracellular dextran formed by cariogenic streptococci. The production of these extracellular polysaccharides therefore seems to be at least partially responsible for the ability of bacteria to induce plaque. This hypothesis helps to explain the unusual specificity which cariogenic bacteria possess in the caries test systems currently in use.