Effect of cigarette smoking on subgingival bacteria in healthy subjects and patients with chronic periodontitis

Background: Cigarette smoking is known to increase the risk of periodontal destruction and developing chronic periodontitis ( CP). It is also reported to affect the subgingival bacterial profile among CP patients. However, studies on the effect of smoking on the bacterial profile among healthy subjects are still limited. Therefore, the aim of this study was to investigate the impact of smoking on the subgingival bacterial profile in both healthy adults and CP patients. Methods: Subgingival plaque samples were collected from CP patients ( 30 nonsmokers and 9 smokers) and healthy subjects ( 37 non- smokers and 18 smokers). Genomic DNA was extracted and 25 bacterial species were detected using PCR of 16S rRNA. Comparing smokers to non- smokers from each group was conducted using chi2 and binary logistic regression analysis. Results: After correcting for confounding factors, the odds of having Slackia exigua, Selenomonas sputigena and Campylobacter rectus was higher among healthy smokers ( ORadj = 10.1, 6.62 and 5.62 respectively). While for CP group, the highest odds were observed for Treponema amylovorum, Treponema medium, Slackia exigua and Treponema vincentii ( ORadj = 20.7, 7.97, 6.37 and 5.37 respectively) and the increase in Treponema amylovorum was statistically significant ( p = 0.05). Conclusion: Smoking affects the subgingival bacterial profile in healthy individuals and is responsible for the depletion of beneficial bacteria and the increase in periodontopathogenic bacteria. In the CP patient group, our study suggests that subgingival bacteria ( particularly Treponema species) make a more substantial contribution in the etiology of CP among non- smokers. Further studies using a larger sample set and more sensitive and quantitative techniques ( such as real - time PCR) are needed to enhance our understanding of the exact effect of smoking on subgingival biofilm.