Molecular identification of porphyromonas gingivalis in the saliva of patients with periodontitis and periodontally healthy individuals attending dental teaching  hospital, Peradeniya

Periodontitis, which affects more than 90% of Sri Lankan adults, can eventually lead to loss of teeth and more serious health complications such as cardiovascular diseases. A keystone pathogen involved in the initiation and progression of periodontitis is Porphyromonas gingivalis. Since P. gingivalis is an anaerobic, slow-growing bacterium, its identification through conventional microbiological techniques is an extremely tedious task. This study aimed to identify salivary P. gingivalis using conventional PCR, compare its detection between individuals with periodontitis and those who are periodontally healthy, and assess the possibility of using salivary P.gingivalis analysis by PCR as a non-invasive screening test for periodontitis risk assessment in Sri Lankan population. For this purpose, unstimulated whole saliva samples were collected from a total of 86 individuals (64 patients with periodontitis and 22 periodontally healthy individuals) aged 18–80 years, attending the Dental Teaching Hospital in Peradeniya. DNA was extracted from samples using a chemical method. PCR amplification was carried out by targeting the 16S rRNA gene of P. gingivalis. The PCR product was visualized using agarose gel electrophoresis. The specificity of the PCR amplicon was verified by Sanger sequencing and comparing it with the reference sequence of P. gingivalis in the NCBI database. P. gingivalis is more frequently detected in periodontitis patients (50.00%; 32/64) compared to periodontally healthy individuals (22.73%; 5/22). The chi-square test demonstrated a significant association between detection of P. gingivalis in saliva and periodontitis, χ2 (5, N=86) = 4.9, p = 0.03. BLAST analysis of the consensus sequence of the PCR product confirmed the specificity of the PCR, showing 100% similarity to the reference P. gingivalis 16S rRNA gene. This study demonstrates the feasibility of non-invasive molecular detection of P. gingivalis in saliva as a potential biomarker for periodontitis in Sri Lankan patients. Further, it lays the foundation for future quantitative analysis of this bacterium using qPCR, for enhancing its application in population-level screening for risk assessment of periodontitis.