Certain bacteria in the mouth have been known to be associated with the development of atherosclerosis, the buildup of fatty deposits in the arteries. But the relationship may go deeper: Oral bacteria can also be transmitted to the gut. In fact, these bacteria in the mouth and the gut may actually be connected, rather than two separate communities of microbes.

Bacteria from your mouth can enter the bloodstream through the gut to cause cardiovascular disease. There also appears to be a connection between the gut microbiome itself and atherosclerosis.

Sixty-four species of bacteria in the gut were associated with the development of atherosclerosis.

A team of Swedish researchers from Uppsala and Lund Universities analyzed cardiac imaging studies and fecal samples from almost 9,000 participants in the Swedish Cardiopulmonary Bioimage Study. Participants were between 50 and 65 years old and about 54 percent of them were women. None of the participants had been diagnosed with atherosclerosis prior to enrolling in the study.

About 40 percent of participants were found to have atherosclerosis in their coronary arteries. More than five percent had at least one coronary artery more than half blocked.

There were 64 species of bacteria in the gut that were associated with the development of atherosclerosis, the team found. This link was strongest for bacteria also found in the mouth.

“The large number of samples with high-quality data from cardiac imaging and gut flora allowed us to identify novel associations” between the gut microbiome and the development of atherosclerosis, Sergei Sayols-Baixeras, of Uppsala University and lead author of the study, said in a statement.

Five species of bacteria in the gut, including three varieties of streptococci, were found to be correlated with the same species in saliva and associated with worse dental health. These bacteria were associated with higher levels of markers of inflammation and infection in the blood. These biomarkers are known to be related to atherosclerosis and poor oral health.

This study only shows an association between the presence of certain bacteria in the gut and atherosclerosis. More studies are needed to determine exactly if and how these 64 species of bacteria cause atherosclerosis.

“We have just started to understand how the human host and the bacterial community in the different compartments of the body affect each other,” senior author, Marju Orho-Melander, of Lund University, said. “We now need to investigate if these bacteria are important players in atherosclerosis development.”

The study is published in Circulation.