Gum bacteria in the bloodstream: a fresh signal for coronary risk

Periodontal pathogens have long been implicated in cardiovascular disease, but direct evidence linking bacterial detection — rather than periodontal diagnosis alone — to coronary heart disease (CHD) has remained limited. This cross-sectional study enrolled 165 patients undergoing coronary angiography (124 with angiographically confirmed CHD, 41 controls) and used TaqMan quantitative PCR to detect Porphyromonas gingivalis (Pg) DNA in both oral samples and peripheral blood. Gut microbiota composition was profiled by 16S rRNA sequencing in a subset.

Oral Pg positivity was more common among CHD patients than controls and remained independently associated with CHD after adjustment (prevalence ratio 1.237, 95% CI 1.044–1.465). The association strengthened further when blood Pg positivity was added: patients positive at both oral and blood sites showed the highest adjusted prevalence ratio (1.362, 95% CI 1.099–1.688), and the association increased stepwise with the number of positive detection sites. Five amplicon sequence variants were significantly enriched in the gut microbiota of oral Pg-positive participants, though predicted functional pathway differences did not survive correction for multiple testing.

The design is cross-sectional and cannot establish causality, and the sample is drawn entirely from patients already referred for angiography — a population enriched for cardiovascular risk. Still, the dose-response pattern (oral-only vs. oral-plus-blood positivity) and the biologically plausible gut microbiota signal add weight to the hypothesis that periodontal pathogen burden, not just periodontal disease status, tracks coronary risk. For clinicians, this reinforces two points: first, periodontal screening has a place in comprehensive cardiovascular risk assessment, even absent a diagnosed periodontal condition; second, systemic dissemination of oral pathogens — detectable in peripheral blood — may be a more informative marker than local disease severity alone. Confirmation in prospective cohorts, with causal-inference designs, is needed before this translates into altered screening protocols.