Brief introduction of bacteria found in bloodstream Several types of bacteria live on the surface of the skin or colonize the moist linings of the urinary tract, lower digestive tract, and other internal surfaces. These bacteria are normally harmless as long as they are kept in check by the body's natural barriers and the immune syst People in good health with strong immune systems rarely develop bacteremia. However, when bacteria are introduced directly into the circulatory system, especially in a person who is ill or undergoing aggressive medical treatment, the immune system may not be able to cope with the invasion, and symptoms of bacteremia may develop Common immediate causes of bacteremia include drainage of an abscess, including an abscessed tooth urinary tract infection, especially in the presence of a bladder catheter decubitus ulcers (pressure sores) intravenous procedures using unsterilized needles, including Iv drug use prolonged IV needle placementBrief Introduction of Bacteria found in Bloodstream. Several types of bacteria live on the surface of the skin or colonize the moist linings of the urinary tract, lower digestive tract, and other internal surfaces. These bacteria are normally harmless as long as they are kept in check by the body ' s natural barriers and the immune system. People in good health with strong immune systems rarely develop bacteremia. However, when bacteria are introduced directly into the circulatory system, especially in a person who is ill or undergoing aggressive medical treatment, the immune system may not be able to cope with the invasion, and symptoms of bacteremia may develop. Common immediate causes of bacteremia include: drainage of an abscess, including an abscessed tooth urinary tract infection, especially in the presence of a bladder catheter decubitus ulcers (pressure sores) intravenous procedures using unsterilized needles, including IV drug use prolonged IV needle placement • • • • • • • u