Plaque Microflora Research Articles

Comparison of the Plaque Microflora in Immunodeficient and Immunocompetent Dental Patients

The nature and extent of the immune dysfunctions in 20 immunodeficient patients, as well as the immunocompetence of 22 control subjects, were verified by cell-mediated responsiveness and immunoglobulin quantitations. Comparisons of the microbial composition of supragingival plaque between the two populations showed that a greater number of immunodeficient than control subjects harbored Candida sp. and Staphylococcus sp. Conversely, a lower number of immunodeficient than control subjects harbored Streptococcus mutans. Also, patients with immune dysfunctions had a lower dental caries experience than their immunocompetent counterparts.

In vitro evaluation of seven cationic detergents as antiplaque agents.

The bactericidal efficacy of seven cationic detergents was studied in vitro against intact performed plaques of representative strains of four oral dental plaque-forming microorganisms: Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Actinomyces naeslundii. Both absolute (plaque bactericidal index) and relative (chlorhexidine coefficient) indexes of antiplaque activity were established. Only cetyltrimethylammonium bromide was more efficacious than the reference agent, the bisbiguanide chlorhexidine, for the apparently more potent tooth-adherent cariogenic and periodontopathic elements, respectively, of the in vivo plaque microflora, S. mutans and A. viscosus.

Stability of the Resident Microflora and the Bacteriocinogeny of Streptococcus mutans as Factors Affecting its Establishment in Specific Pathogen-Free Rats

The outcome of the experimental implantation of Streptococcus mutans strains in humans and animals is unpredictable, and neither success nor failure can be explained. It seems logical to assume that, apart from dietary and host factors, the characteristics of the S. mutans strain involved and those of the resident plaque microflora are important in colonization. For example, previous work in this laboratory suggested that bacteriocin production accounts at least in part for the establishment of an invading bacterium in a microbial ecosystem. In the present study, a complex specific pathogen-free Ny plaque ecosystem was obtained by the inoculation of specific pathogen-free rats with Actinomyces viscosus Ny1 and S. sanguis Ny101, and the establishment of S. mutans in such rats was then examined. It was found that bacteriocinogenic (bac(+)) strains generally colonized in much higher proportions than non-bacteriocinogenic (bac(-)) strains. Moreover, the longer the delay in introducing S. mutans, the poorer was its establishment. Shortly after inoculation of strains Ny1 and Ny101, there is probably a transient state in which microbial equilibrium has not been reached, but later the specific pathogen-free Ny system attains a stable climax community which more strongly resists invaders. The ability of a number of S. mutans strains to establish in such a climax community was then examined, and it was found that bac(+) strains generally established at a higher level than did bac(-) strains. In summary, it was concluded that, although the bac(+) state is an important property in the successful invasion of a plaque by S. mutans, the stability of the resident microflora is also an important factor.

Factors affecting the stability of the resident dental plaque microflora of specific pathogen-free rats in relation to the ability to resist colonization by Streptococcus mutans

Factors that might affect the ability of the resident plaque microflora to resist subsequent challenge with 2 Strep, mutans strains, T2 and OMZ 176 were investigated. Firstly, specific pathogen-free (SPF) rats were fed a sucrose-containing diet for varying periods before challenge; the SPF oral flora was unaffected by the diet and both challenging strains established themselves in high proportions in the plaque. Thus, the SPF flora has a low stability and can easily be disturbed. Secondly the ability to resist colonization by Strep, mutans strains was studied in rats harbouring the SPF flora containing Actiniomyces viscosus Ny 1, Strep, sanguis Ny 101 or both. Only A, viscosus Ny 1, alone or in combination with Strep, sanguis Ny 101, affected the establishment of Strep, mutans. Also, the longer the resident microflora was allowed to equilibrate before Strep, mutans challenge, the less was the chance of establishment. The findings are relevant to the development of a plaque flora capable of reducing dental caries by preventing the establishment of organisms such as Strep, mutans.

Rapid method for identification and enumeration of oral Actinomyces.

Serotype-specific antisera prepared against whole cells of Actinomyces viscosus, A. naeslundii, and A. israeli were labeled with fluorescein dye and used to detect and quantitate antigenically related microorganisms in human dental plaque. By relating the DNA content of the dental plaque microflora to the number of Actinomyces present in the plaque samples, a reproducible method was developed for specifically enumerating five serotypic representatives of this genus found in human plaque.

Development of bacterial plaque in the oral cavity

Dental plaque may be defined as bacterial aggregations upon the teeth and other solid structures inserted in the oral cavity. It is formed by oral microorganisms which attach to the teeth in sheltered areas along the gingival margin, on the approximal surfaces, and in pits and fissures on the masticatory surfaces. The plaque increases in quantity either by multiplication of already attached organisms, or by continuous addition to the deposits of bacteria from the saliva. Structural analyses indicate that the organisms are held together in an exracellular matrix partly produced by the organisms and partly derived from saliva. The microflora of plaque is complex and shows great individual variation. There are also characteristic differences in plaque from different sites on the teeth. Thus dento-gingival plaque is qualitatively different from that of the occlusal fissures. Furthermore, the relative proportion of different types of microorganisms may vary with the age of the deposit. Such information must be taken in consideration when attempts are made to develop chemical agents for the purpose of inhibiting plaque formation in order to prevent periodontal disease and caries.

Effects of a Bacteriolytic Enzyme from Streptomyces globisporus on Microflora of Human Dental Plaque and Tongue Coating

Effects of a Bacteriolytic Enzyme from Streptomyces globisporus on Microflora of Human Dental Plaque and Tongue Coating

The novel structure of a microorganism of human gingival plaque

Electron-microscopic examination of gingival plaque microflora showed a bacillus-like, microencapsulated, thick-walled organism with a previously unreported structure. This structure, which is not an example of fimbriae, flagellae, or attached extracellular polysaccharide, is a tuft of thin fibers about 0.3 μm long at only one end of the cell. The fibers begin in or near to the cell wall and pass through the microcapsule to the outside. The name lotussy is proposed for this new structure and the name lotuslifa for an individual fiber or filament.

Histotopochemical determination of metabolic activity of carbohydrate metabolism in plaque from sound and carious enamel.

The tetrazolium technique was applied in tissue sections from sound and carious enamel plaque on human teeth to represent the histotopochemical distribution of activity for numerous enzymes of the Embden-Meyerhof pathway, the pentosephosphate and citrate cycle, and the glycerophosphate cycle. GAPDH, LDH, G6PDH, ME, MDH, SDH, and NAD-IDH were found in all samples from sound enamel plaque; NADP-IDH appeared in a few. In plaque from carious enamel, all enzymes tested were found constantly in all samples. There was high enzyme activity in the outer bacterial layer of plaque from sound enamel, whereas the bacterial layer adjacent to the enamel showed substantially less activity. In contrast to the other enzymes, LDH generally showed a relatively low level of activity with signs of stronger activity in the inner layer adjacent to the enamel than in the outer layer. In plaque from carious enamel, the activity of the enzymes tested showed a definite increase from the outer to deeper layers, and was highest in the bacterial layer next to the enamel. The distribution pattern of LDH coincided with that of the other enzymes tested. A semi quantitative differentiation of enzyme activity in the two types of plaque showed that microorganisms in plaque from carious enamel have greater catalytic activity in carbohydrate metabolism than comparable microflora in plaque from sound enamel. From a functional point of view, the total biotope plaque was subdivided into further partial biotopes, characterized by different enzymic activities.

The effect of sorbitol on the microbiology of the dental plaque in monkeys ( Macaca irus)

A group of 4 monkeys was fed an essentially sucrose-free diet containing approximately 1 g/day sorbitol. The animals were infected with plaque from a cariesactive monkey and the population of Streptococcus mutans in plaque was determined over a period of weeks. A further group of 4 monkeys with an already established population of Strep. mutans in plaque was also fed a sorbitol-containing diet. The results obtained suggest that sorbitol will neither aid the implantation nor support the continuance of populations of Strep. mutans in plaque. All eight monkeys were included in experiments to determine whether adaptive processes occurred in the plaque microflora during prolonged consumption of sorbitol. pH measurements were carried out using antimony micro-electrodes and the number of sorbitol-fermenting organisms in plaque monitored over a 2-yr period. The capacity of plaque to produce acid from sorbitol remained unaltered during the experimental period and no increase in the numbers of sorbitol-fermenting organisms was noted. Large amounts of plaque were present in the sorbitol-fed monkeys but only one animal developed two small carious lesions after 3 yr consumption of a sorbitol-containing diet. Each of six control, sucrose-fed monkeys developed caries with multiple extensive lesions during the same period. The results suggest that long-term consumption of sorbitol is unlikely to induce the formation of plaque capable of the rapid fermentation of sorbitol to low pH values.