Presence of Porphyromonas gingivalis in Subgingival Plaque-Biofilm of Elderly People

Objectives: The frequency of periodontal diseases appears to increase with age. However, few have been investigated to subgingival microflora in elderly people. Porphyromonas gingivalis is widely regarded as major periodontal pathogens. This study aimed to quantify P. gingivalis in subgingival plaque biofilm of elderly people by real-time PCR.

Methods: After informed consent was obtained from each subject, 251 females and 123 males over 60 year-old (mean age 70.4±6.5) of independent elderly subjects, were investigated. The gingival crevice with the deepest probing depths were chosen as the target sites of sampling, and then the subgingival plaque samples were obtained using sterile toothpicks. Genomic DNA was extracted, and quantification of total and target bacteria was performed by real-time PCR using universal and species-specific primers based on 16S rRNA genes, respectively, and the proportion of P. gingivalis was calculated.

Results: One hundred seventy-six elderly subjects (mean age 70.6±6.5) were contracted periodontitis (probing depth of ≥4 mm), and 198 elderly subjects (mean age 70.3±6.5) were periodontally healthy (<4mm). The detection frequency of P. gingivalis was 69.3 and 46.0%, respectively, and it was significantly higher in the periodontitis subjects (P<0.0001). The mean proportion of P. gingivalis was 0.58±1.59 and 0.10±0.28%, respectively, and it was higher in periodontitis subjects (P<0.0001), especially in subjects of deep (≥6 mm) periodontal pockets (mean 1.26±2.65%), while its proportion was not significantly related to subjects' gender, age and presence of denture.

Conclusions: P. gingivalis was detected frequently both from periodontitis subjects and even from periodontally healthy subjects (of elderly people). These results suggest that P. gingivalis inhabits oral cavities of not only periodontitis subjects but also periodontally healthy subjects of elderly people, and that the inhabitation of P. gingivalis is a specific feature of subgingival plaque biofilm of elderly people. Supported by TUGSD Young Dental Researchers Encouragement Program in 2007-2008.