Identification of Bacteria Associated with Chronic Periodontitis 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 determine the subgingival microbial profile in healthy and disease sites of smokers suffering from chronic periodontitis using 16S cloning and sequencing. Methods: 15 current smokers over 30 years of age, suffering from generalized moderate to severe chronic periodontitis and with at least 20 natural teeth were selected. Subgingival plaque samples were collected on paper points from four disease (PD>5mm) sites and pooled. Similar samples were collected from four healthy (PD<4mm) sites and separately pooled. 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 deep and shallow site providing 95% confidence of detecting species present at greater than or equal to 3% of the total flora. Bacterial profiles of diseased and healthy sites were compared using non-parametric tests. Results: Few differences were observed between the bacterial communities in diseased and healthy sites. 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 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.