Microbial composition of atherosclerotic plaques

OBJECTIVE

The association of infections such as periodontitis with atherosclerotic diseases is well documented. In spite of the high diversity of the human oral microbiota, and its close contact with the circulatory system, few oral species were detected in atherosclerotic plaques. Thus, we attempted to evaluate the microbial diversity of atherosclerotic plaques from patients with different periodontal conditions, submitted to endarterectomy by a broad-range microbial method.

MATERIALS AND METHODS

Patients indicated for aorta endarterectomy due to myocardial infarction were recruited for periodontal clinical examination. The microbial diversity of atherosclerotic plaques (n = 35) was evaluated by sequence analysis of bacterial 16S rRNA libraries.

RESULTS

Bacterial DNA was detected in 12 endarterectomy specimens (34.3%). Twenty-three bacterial species/phylotypes were identified. Proteobacteria and Firmicutes comprised 78.3% and 21.7% of the identified taxa, respectively. Fifteen (60.9%) phylotypes were reported as yet uncultivable or as yet uncharacterized species. Two uncultured phylotypes were previously detected in the human mouth. The periodontopathogen Aggregatibacter actinomycetemcomitans was detected in seven samples (20%), followed by Pseudomonas species. There was no association between periodontal parameters and detection of A. actinomycetemcomitans or other phylotypes in atherosclerotic plaques.

CONCLUSION

Our results suggest a role of the oral microbiota in the development of inflammation in atherogenesis, particularly of A. actinomycetemcomitans.

Antibacterial Activity of Various Self-etching Adhesive Systems Against Oral Streptococci

An antimicrobial effect is desired for adhesive systems in order to avoid cariogenic bacterial colonization and also the growth of remaining bacteria in the cavity preparation.

Aggregatibacter actinomycetemcomitans arcB influences hydrophobic properties, biofilm formation and adhesion to hydroxyapatite

The regulation of gene expression in the oral pathogen Aggregatibacter actinomycetemcomitans is still not fully elucidated. ArcAB is a two-component system which allows facultative anaerobic bacteria to sense various respiratory growth conditions and adapt their gene expression accordingly.This study investigated in A. actinomycetemcomitans the role of ArcB on the regulation of biofilm formation, adhesion to saliva coated hydroxyapatite (SHA) and the hydrophobic properties of the cell. These phenotypic traits were determined for an A. actinomycetemcomitansarcB deficient type and a wild type strain. Differences in hydrophobic properties were shown at early and late exponential growth phases under microaerobic incubation and at late exponential phase under anaerobiosis.The arcB mutant formed less biofilm than the wild type strain when grown under anaerobic incubation, but displayed higher biofilm formation activity under microaerobic conditions. The adherence to SHA was significantly lower in the mutant when compared with the wild type strain. These results suggest that the transmembrane sensor kinase ArcB, in A. actinomycetemcomitans, senses redox growth conditions and regulates the expression of surface components of the bacterial cell related to biofilm formation and adhesion to saliva coated surfaces.

16S rRNA region based PCR protocol for identification and subtyping of Parvimonas micra

The present study established a PCR protocol in order to identify Parvimonas micra and to evaluate the intra-species diversity by PCR-RFLP of 16S rRNA partial sequence. The data indicated that the protocol was able to identify this species which could be clustered in five genotypes.

Genotypic and phenotypic analysis of Streptococcus mutans from different oral cavity sites of caries-free and caries-active children

INTRODUCTION

Streptococcus mutans exhibits extensive genotypic diversity, but the role of this variation is poorly understood. This study aimed to determine the number and distribution of genotypes of S. mutans isolated from caries-active and caries-free children and to evaluate some of their phenotypic traits.

METHODS

Stimulated saliva, tongue surface and biofilms over sound and carious teeth surfaces were sampled from 10 caries-free and 11 caries-active children aged 5-8 years. A total of 339 isolates of S. mutans were genotyped by arbitrarily primed polymerase chain reaction using OPA2 primer. One isolate from each genotype was tested for its acid susceptibility and its ability to form a biofilm.

RESULTS

Fifty-one distinct genotypes were determined, one to three genotypes in each oral sample. A single genotype was detected in seven children, whereas the remaining 14 children exhibited two to seven genotypes. There were no significant differences in the number of genotypes detected in caries-free and caries-active children. No correlation was observed between the number of genotypes and the mutans streptococci salivary levels. Five of the six high biofilm-forming genotypes were obtained from caries-active children, although the differences in biofilm formation between isolates from caries-free and caries-active children were not statistically significant. Genotypes with low susceptibility to acid challenge were statistically more frequent among isolates from caries-active children than among those from caries-free children.

CONCLUSION

The present data suggested that there were differences in the distribution of genotypes of S. mutans according to the oral site and that S. mutans populations differ in their acid susceptibility and ability to form biofilms, factors allowing their colonization of sucrose-rich environments.

Distribution of fimA genotypes of Porphyromonas gingivalis in subjects with various periodontal conditions

Fimbria encoded by the gene fimA is considered one of the main factors in the colonization of the oral cavity by Porphyromonas gingivalis. Allelic variation in fimA led to the classification of strains of P. gingivalis into six genotypes. The occurrence of P. gingivalis was determined by polymerase chain reaction using 16S rRNA primers in 302 subgingival samples obtained from 102 Brazilian subjects exhibiting different periodontal conditions. Distribution of fimA genotypes was assessed in 146 P. gingivalis positive samples by polymerase chain reaction using primers pairs homologous to the different fimA genes. P. gingivalis was detected in 51 of 57 (89.4%) patients with periodontal attachment loss, in six of 20 gingivitis patients (30.0%) and in two of 25 (8.0%) subjects with a healthy periodontium. Variant type II was the only type detected in 53 sites (39.3%), distributed among 19 periodontitis patients (37.3%) and in one patient with no periodontal destruction. Type Ib was the second most prevalent genotype in periodontitis patients (19.6%). Genotype V was not detected in the studied population. Type IV was the most commonly type found among gingivitis patients, either alone or in combination with other genotypes. Multiple genotypes were detected in nine sites (6.1%). A fimA genotype was not identified in 26 sites (17.8%) of 146 sites positive for P. gingivalis, suggesting that other alleles of fimA not yet sequenced may be prevalent in this population. These data demonstrated that P. gingivalis type II strains followed by type Ib are more prevalent in periodontitis patients from a multiracial population in Brazil, suggesting an increased pathogenic potential of these types.