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Chronic periodontitis is an inflammatory disease of the periodontium affecting nearly 65 million adults in the United States. Changes in subgingival microbiota have long been associated with chronic periodontitis. Recent culture-independent molecular studies have revealed the immense richness and complexity of oral microbial communities. However, data sets across studies have not been directly compared, and whether the observed microbial variations are consistent across different studies is not known. Here, we used 16S rRNA sequencing to survey the subgingival microbiota in 25 subjects with chronic periodontal disease and 25 healthy controls and compared our data sets with those of three previously reported microbiome studies. Consistent with data from previous studies, our results demonstrate a significantly altered microbial community structure with decreased heterogeneity in periodontal disease. Comparison with data from three previously reported studies revealed that subgingival microbiota clustered by study. However, differences between periodontal health and disease were larger than the technical variations across studies. Using a prediction score and applying five different distance metrics, we observed two predominant clusters. One cluster was driven by Fusobacterium and Porphyromonas and was associated with clinically apparent periodontitis, and the second cluster was dominated by Rothia and Streptococcus in the majority of healthy sites. The predicted functional capabilities of the periodontitis microbiome were significantly altered. Genes involved in bacterial motility, energy metabolism, and lipopolysaccharide biosynthesis were overrepresented in periodontal disease, whereas genes associated with transporters, the phosphotransferase system, transcription factors, amino acid biosynthesis, and glycolysis/gluconeogenesis were enriched in healthy controls. These results demonstrate significant alterations in microbial composition and function in periodontitis and suggest genes and metabolic pathways associated with periodontal disease., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

The squirrel monkey (Saimiri sciureus) has been proposed as an in vivo model for the study of subgingival colonization by suspected periodontopathogens, such as black-pigmented porphyromonads and prevotellas (BP/P). However, the indigenous microbiota of the squirrel monkey has not been well described. Therefore, in order to more fully characterize the oral microbiota of these animals, we studied two groups of squirrel monkeys from widely different sources. Group I consisted of 50 breeding colony monkeys ranging in age from 9 months to over 6 years which had been raised in captivity; group II consisted of 16 young sexually mature monkeys recently captured in the wild in Guyana. Group I animals in captivity had developed moderate to severe gingivitis, with a mean gingival index (GI) of 2.6; 52% of the sites bled, 26% had detectable calculus, and 83% had detectable BP/P. A group I subset (six animals), for which predominant cultivable microbiota was described, had a mean GI of 2.4. Colony morphology enumeration revealed that five of the six subset animals were detectably colonized with BP/P (range, 0 to 16.9%) and Actinobacillus actinomycetemcomitans (range, 0 to 3.9%); all subset animals were colonized with Fusobacterium species (range, 0.8 to 3.6%), Actinomyces species (range, 2.3 to 11%), and gram-positive cocci (range, 1.4 to 21.4%). Predominant cultivable microbiota results revealed the presence of many bacterial species commonly found in the human gingival sulcus. At baseline, group II animals were clinically healthy and had a mean GI of 1.4; 67% of the sites bled and 2.1% had calculus, and none of the animals had detectable BP/P. Neisseriae were very common in noninflamed sites. Subsequently, when inflamed sites were compared with noninflamed sites in group II animals after they had been maintained in captivity for 6 months, inflamed sites exhibited a more complex microbiota and increased proportions of gram-negative rods and asaccharolytic bacteria.

Colonization of the gingival crevice by black-pigmented Porphyromonas or Prevotella spp. (BP/P), including Porphyromonas gingivalis (formerly Bacteroides gingivalis) and Prevotella intermedia (formerly Bacteroides intermedius), is thought to be an important ecological event which may result in the destruction of connective tissues supporting the teeth. Theoretically, periodontal diseases could be prevented if these or other periodontal pathogenic microorganisms did not colonize the subgingival area. The humoral immune response is one mechanism which may modulate bacterial colonization in the gingival crevice. In the present study, we tested the effect of systemic humoral immunity on subgingival colonization by indigenous P. intermedia in squirrel monkeys (Saimiri sciureus). Animals rendered essentially free of detectable BP/P by a single scaling, 10 days of tetracycline therapy, and toothbrushing three times per week were immunized with P. intermedia 1447 or were sham immunized with phosphate-buffered saline. Subsequently, all oral hygiene procedures were discontinued and five teeth in one quadrant were ligated with bacterium-soaked suture material to facilitate BP/P colonization. Immunization resulted in a significant increase in the level of immunoglobulin G anti-P. intermedia antibody in serum. Two weeks after ligation was initiated, P. intermedia could be detected in five of six sham-immunized and three of six immunized animals. Immunization was associated with a reduction in the emergence of indigenous P. intermedia in the gingival crevice.

The objective of this study was to determine whether the squirrel monkey (Saimiri scuireus) is indigenously colonized with black-pigmented bacteroides (BPB) resembling human Bacteroides gingivalis and Bacteroides intermedius (suspected periodontal pathogens) and to determine the usefulness of the squirrel monkey as an in vivo model for studying colonization by putative pathogens. We assayed the subgingival plaques of 138 monkeys of various ages and in four different colonies for the presence of anaerobic BPB microorganisms. We also tested half the animals for the presence of Actinobacillus actinomycetemcomitans. Clinical indices and levels of serum antibody to B. gingivalis were recorded. We detected BPB in 50% of the animals and A. actinomycetemcomitans in 69% of the animals. The presence of BPB was generally associated with increased age, increased gingival index, presence of calculus, and increased levels of serum antibody. These data indicate that the squirrel monkey may be a good model for studying the parameters of natural infection of the gingival crevice with suspected periodontopathogenic BPB microorganisms.

Periodontal diseases are inflammatory responses thought to be triggered by specific microorganisms colonizing in the gingival crevice. Theoretically, periodontal diseases could be prevented if the etiologic organisms were not allowed to colonize the subgingival area. The humoral immune response is one mechanism which may modulate bacterial colonization in the gingival crevice. To test the effect of systemic humoral immunity on subgingival colonization by bacteria, squirrel monkeys (Saimiri sciureus) were immunized with Bacteroides gingivalis, a black-pigmented Bacteroides sp. and putative periodontal pathogen. Immunized and sham-immunized monkeys were orally inoculated with 10(10) viable B. gingivalis during ligation of five teeth in one quadrant with bacterium-soaked suture material and distribution over the entire dentogingival margin. Immunization resulted in an increased level of immunoglobulin G anti-B. gingivalis in serum and was associated with a strong trend toward a statistically significant reduction in colonization of the gingival crevice by black-pigmented bacteroides.