Quantitative Analysis of the Subgingival Microbial Community in Current Smokers

Introduction: Smoking is established as a risk factor for periodontitis and is responsible for 41.9% of periodontitis in the USA. Although both bacterial plaque and smoking play important roles in periodontitis, associations between individual species or bacterial consortia and smoking have not been well elucidated. Objective: The purpose of the present study was to compare the subgingival microbial profile of periodontally healthy smokers to those suffering from chronic periodontitis using 16S cloning and sequencing. Methods: 15 current smokers suffering from generalized moderate to severe chronic periodontitis and 15 age-matched periodontally healthy smokers were selected. From the disease group, subgingival plaque samples were collected on paper points from four disease (PD>or=5mm) sites and pooled. Similar samples were collected from four healthy (PD>or=3mm) sites and separately pooled. From the healthy group, plaque was collected and pooled from every tooth. DNA was isolated from these samples and 16S rRNA genes amplified using PCR with broad range primers. The amplicons were cloned into E.coli and the inserts sequenced for bacterial identification. 100 clones were identified from each sample providing 95% confidence of detecting species present at greater than or equal to 3% of the total flora. Bacterial profiles of disease and healthy subjects were compared using non-parametric tests. Results: Few differences were observed between the bacterial communities in diseased and healthy subjects. Several species of the genera Filifactor, Selenomonas, Peptostreptococcus, Campylobacter and Streptococcus were dominant members of the community. Uncultivated species accounted for the majority of the bacteria detected. The genera Bacteroides or Porphyromonas were seldom detected, indicating that they are not generally present at high levels in these subjects. Conclusions: The predominant flora in smokers with and without chronic periodontitis consists of species from the genera Filifactor, Selenomonas, Peptostreptococcus, Campylobacter and Streptococcus. Traditional periodontopathogens were numerically minor constituents of the subgingival microbial community.