The disease is called subacute bacterial endocarditis, a severe infection of the heart lining. In this condition bacteria collect at a previously-damaged site within the heart. The prior damage can be from rheumatic fever, congenital defects, and other causes. Frequently, victims are unaware of this pre-existing damage. Doctors call this unauthorized use of the circulatory system bacteremia.
Bacteria enter the body through a failure of natural defensive barriers.
One such barrier is skin. Another is the tooth structure. The only oxygen in the blood is wrapped up inside red corpuscles. There is one part of the human body which is consistently at or near internal body temperature, is rich in microscopic nourishment, is extremely moist and slightly saline, and is anaerobic. It is also on the outside of a barrier surface.