Blood is a normally sterile fluid, and the presence of any type of microorganism is a cause of concern for the person infected. When discussing the presence of microorganisms in the blood, the suffix "-emia" is used--bacteremia, septicemia, parasitemia, fungemia and viremia, for example. Infections of the blood can have serious immediate consequences since they also threaten every organ of the body. Infections of the bloodstream are among the most serious infectious diseases.
Bacteremia and Septicemia
Bacteria in the blood can occur transiently, such as after minor trauma like brushing your teeth or a strained bowel movement. Intermittent bacteremia is when bacteria is periodically released into the blood, such as from an abscess, and continuous bacteremia is when the bacterial infection is intravascular. Many bacteremias are removed from circulation by phagocytes and signs and symptoms of infection are variable. Septicemia is a clinical syndrome characterized by toxin production, fever, chills, shock and even death. This usually occurs when when circulating bacteria in the blood multiplies at a rate faster than they can be removed from the bloodstream. Any bacteria can be involved in bacteremia, including staphylococci, streptococci and other related bacterial species. Sepsis is usually associate with gram-negative bacilli like E.coli, which contain a toxin in its cell wall. However, gram-positive bacteria like Staphylococcus aureus can also cause sepsis.
Parasitemia
The presence of parasites in the blood can never be considered a positive health situation. Many parasites that cause infections in the blood are some of the most severe and feared diseases. In malaria for example, parasites invade the person's red blood cells, causing destruction of the cells and resulting in anemia. Falciparum malaria, the fatal form of the disease, can result in the trapping of normal red blood cells with the infected red blood cells and the clogging of vessels to the brain, which is typically fatal. Other parasitic infections of the blood include the parasites that cause Chagas disease, sleeping sickness and babesiosis.
Fungemia
The presence of fungi, yeasts and molds in the blood usually signals a serious infection. Fungal infections of the blood are frequently associated with people who are immuno-compromised, such as AIDS patients, people on chemotherapy and other conditions or medications that depress the immune system. The most common fungal infections of the blood include candidiasis and histoplasmosis. The fungi in the blood can disseminate to other organs of the body, where they can grow, multiply and produce toxins.
References
- CDC: Malaria
- Todar's Online Textbook of Bacteriology: Bacterial Endotoxins
- "Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 6th Ed."; Elmer Koneman, M.D.; 2006
