Background An increased risk of atherothrombotic vascular events has been reported in periodontitis patients. Periodontitis is associated with dysbiotic subgingival biofilms and bacteremia. Objective We hypothesized (a) that the oral microbiome is associated with the carotid microbiome and (b) that periodontitis could contribute to plaque vulnerability. The aim of this study was to determine the associations between periodontitis, the carotid microbiome, and the local innate immune response in carotid atherothrombotic plaques vulnerable to rupture. Methods In this cross‐sectional study, 45 patients admitted for carotid endarterectomy underwent a preoperative periodontal examination. The volume of intraplaque hemorrhage reflected by the hemoglobin level released in carotid‐conditioned media was considered as a criterion of carotid plaque vulnerability. Levels of antibodies against periodontal bacteria were determined in sera. The signature of the oral microbiota was assessed by microbial whole‐genome sequencing, nested PCR, and immunostaining in carotid plaque samples. Markers of neutrophil recruitment (leukotriene B4), neutrophil activation (myeloperoxidase, defensins), and cytokines were measured in carotid‐conditioned media and/or plasma. Results All patients exhibited periodontitis. One hundred and forty‐four bacterial genera were detected in the carotid microbiome. While Streptococcus was found in 84% of the carotid samples, periodontitis‐associated genera were detected in 21%. P. gingivalis DNA and gingipains were also identified in carotid samples. There were significant inverse correlations between periodontal attachment loss/serum anti‐P. gingivalis Immunoglobulin A and cytokine inhibiting neutrophils (all P < .01). There were also significant positive correlations between lipopolysaccharides, myeloperoxidase/human neutrophil peptides1‐3, and hemoglobin levels (all P < .01). Conclusions In patients at risk of stroke, the carotid plaque microbiome was highly diverse and compatible with an oral origin. Periodontitis was significantly associated with neutrophil activation markers and plaque vulnerability to rupture.

Atherothrombosis, leading to stroke and myocardial infarction, is responsible for most of the deaths in the world. An increased risk of atherothrombotic vascular events has been reported in patients with periodontitis. Periodontitis is a chronic multifactorial inflammatory disease, which involves a dysbiotic microbiota, and leads to a progressive destruction of the tooth-supporting apparatus. Transcient periodontal pathogen blood translocation, mainly bacteremia, has been associated with the severity of gingival inflammation. The identification of periodontal bacteria within atherothrombotic plaques is challenging and unpredictable. This review aims to summarize existing molecular technics for identifying periodontal microbiota in human atherothrombotic samples. A secondary objective is to describe a protocol for the identification of Porphyromonas gingivalis from highly calcified, atherothrombotic human samples that is based on our experience in translational cardiovascular research. Compared to direct real-time PCR, our protocol based on nested PCR has increased the detection of Porphyromonas gingivalis by 22.2% with good specificity. ARTICLE HISTORY