Links between gut microbiota and coronary atherosclerosis have been studied primarily in symptomatic patients who were likely receiving therapies that may have shifted the balance of different organisms; there are fewer data from people with asymptomatic coronary disease.
Oral bacterial species are commonly transmitted to the gut, suggesting that gut and oral microbiota profiles are related and, further, that the gut may allow oral pathogenic bacteria to enter the circulation.
The current study included 8973 adults (53.7% women) without cardiovascular (CV) disease for whom adequate imaging and other data were available from the Swedish Cardiopulmonary Bioimage Study (SCAPIS) and the Malmö Offspring Study (MOS).
Researchers looked for associations between coronary artery calcium (CAC) scores (an index of atherosclerosis), gut bacterial species (identified in fecal samples), oral flora and pathologies, and systemic inflammatory biomarkers.
Among the 64 species that correlated with CAC scores independently of CV risk factors, 51 showed a positive association, especially S anginosus and S oralis subsp oralis; patients with higher levels of those two species generally had more CV risk factors.
Twenty-five bacterial species that correlated with CAC scores were also associated with any coronary plaque by CT angiography. Five such species were associated with coronary stenosis >50%, 39 with the modified Duke index, and five with carotid plaques (P < .05).
Of 54 species positively associated with CAC scores, 13 also tracked with C-reactive protein levels by high-sensitivity assay, 10 with leukocyte counts, and 11 with neutrophil counts (P < .05).
Bacterial species common in the oral cavity made up most of the species that correlated with all three inflammatory biomarkers; they included the streptococci most strongly correlating with CAC scores, that is, S anginosus, S oralis subsp oralis, and S parasanguinis.
If the associations between gut bacterial species and markers of coronary atherosclerosis are found to be causal, such bacteria may "contribute to atherogenesis by direct infection or by altering host metabolism," the report states. "Future studies will show whether these species can be used as potential biomarkers or treatment targets."