Associations between smoking, disease, and Porphyromonas gingivalis fimA genotype distribution: Insights from Korean periodontitis patients

Objective: To investigate the distribution of Porphyromonas gingivalis fimA genotypes in relation to smoking and periodontitis severity in a Korean adult population, and to assess genotype-specific associations with host and environmental factors. Design: Subgingival biofilm samples were obtained from 283 adults, comprising 102 non-smoking healthy individuals, 98 non-smoking periodontitis patients, and 83 smoking periodontitis patients. Bacterial DNA was extracted and analyzed using fimA-specific PCR to detect P. gingivalis and its six fimA genotypes (I, II, III, IV, V, and Ib). Statistical analyses were performed using Fisher's exact test and logistic regression models. Results: Type II fimA was the most common genotype across all groups and was significantly more prevalent in periodontitis patients. Fisher's exact test revealed significant differences in genotype distribution between healthy and diseased individuals, except for types I and III. Logistic regression showed that P. gingivalis detection was strongly associated with disease stage (odds ratio: 7.5), with type II fimA linked to advanced disease. Types IV and Ib were significantly associated with smoking and age, suggesting differential responses of specific genotypes to environmental exposure. Conclusions: Given the distinct associations between fimA genotypes and smoking, careful consideration of strain selection is crucial for future studies investigating P. gingivalis pathogenesis. This study underscores the importance of genotype-specific microbial analyses in elucidating mechanisms of periodontitis progression and highlights the potential for environmental factors such as smoking to shape microbial variation at the strain level.