In later life atherosclerotic plaques grow in blood vessel walls to narrow and weaken those vessels. When a plaque becomes unstable and ruptures, a downstream blockage can cause a heart attack or stroke. This and the slower harmful consequences of reduced blood flow via narrowed vessels makes atherosclerosis the largest cause of human mortality. Here, researchers provide evidence for long-lasting bacterial infection to be involved in the timing of plaque instability and rupture, particularly oral bacteria that have at some point entered the bloodstream. That said, at the point at which plaque is large enough to do this, some form of catastrophe is inevitable. The bacteria are just accelerating the process.
Using a range of advanced methodologies, the research found that, in coronary artery disease, atherosclerotic plaques containing cholesterol may harbour a gelatinous, asymptomatic biofilm formed by bacteria over years or even decades. Dormant bacteria within the biofilm remain shielded from both the patient's immune system and antibiotics because they cannot penetrate the biofilm matrix. A viral infection or another external trigger may activate the biofilm, leading to the proliferation of bacteria and an inflammatory response. The inflammation can cause a rupture in the fibrous cap of the plaque, resulting in thrombus formation and ultimately myocardial infarction.
"Bacterial involvement in coronary artery disease has long been suspected, but direct and convincing evidence has been lacking. Our study demonstrated the presence of genetic material from several oral bacteria inside atherosclerotic plaques." Tissue samples were obtained from individuals who had died from sudden cardiac death, as well as from patients with atherosclerosis who were undergoing surgery to cleanse carotid and peripheral arteries. Researchers developed an antibody targeted at the discovered bacteria, which unexpectedly revealed biofilm structures in arterial tissue. Bacteria released from the biofilm were observed in cases of myocardial infarction. The body's immune system had responded to these bacteria, triggering inflammation which ruptured the cholesterol-laden plaque.
Link: https://www.tuni.fi/en/news/myocardial-infarction-may-be-infectious-disease
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