Ecology of volatile sulfur compound producing microbiota in health and chronic periodontitis

Objectives: Sulfur metabolism of the oral microbiota confers selective advantages during an inflammatory challenge, and is consistent with increased volatile sulfur compound (VSC) concentrations in the breath of periodontitis patients. The aim of this study was to elucidate the VSC producing bacterial taxa in the oral cavity of subjects with chronic periodontitis, gingivitis and periodontal health, and study the ecology between these disease states.
Methods: Tongue scrapings, subgingival and interdental plaque were collected from individuals with gingivitis (n=19), chronic periodontitis (n=14) and periodontal health (n=18). DNA extracted from the samples was analysed by HOMINGS (Human Oral Microbe identification by Next Generation Sequencing), to determine the percentage abundance of 667 oral taxons (538 species and 129 genera). VSC producing species were established by database searches for taxons carrying genes involved in VSC production (cysteine desulfhydrases and methionine gamma lyases). Principal Component and Partial Least Squares mutivariate analyses was used to determine the taxons that influenced the community structure of samples.
Results: Interdental plaque was significantly more rich compared to tongue and subgingival plaque across all cohorts. Subgingival plaque and tongue communities were more alike than interdental plaque in health, however, a transition to less rich and overlapped communities between all niches in gingivitis and chronic peridontitis was observed. VSC producing species were the major drivers of the ecological shifts occurring in the three niches between health, gingivitis and chronic periodontitis. Species with a higher rate of VSC production in vitro such as Treponema spp, Fusobacterium spp. and Porphyromonas endodontalis were strong determinants of the community structure of interdental and subgingival niches in chronic periodontitis and gingivitis.
Conclusions: Overlap of tongue communities within interdental and subgingival niches in chronic periodontitis highlights the role of the tongue microbiota. VSC producing species driving the differentiation of subgingival and interdental niches in chronic periodontitis from health suggests VSC production in these niches could be important in the aetiopathogenesis of chronic periodontitis.