Bacteremia

Definition

Bacteremia is an invasion of the bloodstream by bacteria.

Description

Bacteremia occurs when bacteria enter the bloodstream. This may occur through a wound or infection, or through a surgical procedure or injection. Bacteremia may cause no symptoms and resolve without treatment, or it may produce fever and other symptoms of infection. In some cases, bacteremia leads to septic shock, a potentially life-threatening condition.


Risk factors

Any opening through the skin and/or body orifices that allows for the entrance of bacteria into the body places an individual, particularly those with a compromised immune system, at increased risk for the development of bacteremia.

Conditions that increase the chances of developing bacteremia include:



Causes

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. For this reason, bacteremia is most common in people who are already affected by or being treated for some other medical problem. In addition, medical treatment may bring a person in contact with new types of bacteria that are more invasive than those already residing in that person's body, further increasing the likelihood of bacterial infection.

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
  • use of ostomytubes, including gastrostomy (surgically making a new opening into the stomach), jejunostomy (surgically making an opening from the abdominal wall into the jejunum), and colostomy (surgically creating an articifical opening into the colon)

The bacteria most likely to cause bacteremia include members of the Staphylococcus, Streptococcus, Pseudomonas, Haemophilus, and Esherichia (E. coli) genera.

Symptoms

Symptoms of bacteremia may include:

  • fever over 101°F (38.3°C)
  • chills
  • malaise
  • abdominal pain
  • nausea
  • vomiting
  • diarrhea
  • anxiety
  • shortness of breath
  • confusion

Not all of these symptoms may be present. In the elderly, confusion may be the only prominent symptom. Bacteremia may lead to septic shock, whose symptoms include decreased consciousness, rapid heart and breathing rates, and multiple organ failures.

Tests

Bacteremia is diagnosed by culturing the blood for bacteria. Samples may need to be tested several times over several hours. Blood analysis may also reveal an elevated number of white blood cells.

Treatment

Bacteremia may cause no symptoms, but may be discovered through a blood test for another condition. In this situation, it may not need to be treated, except in patients especially at risk for infection, such as those with heart valve defects or whose immune systems are suppressed.

Drugs

Prompt antibiotic therapy usually succeeds in clearing bacteria from the bloodstream. Recurrence may indicate an undiscovered site of infection. Untreated bacteria in the blood may spread, causing infection of the heart (endocarditis or pericarditis) or infection of the covering of the central nervous system (meningitis).

Blood pressure is monitored closely; a decline in blood pressure may indicate the onset of septic shock.

Prognosis

If detected and treated promptly, most individuals recover from bacteremia. However, in individuals whose immune systems are compromised, it is critical that the condition be treated promptly and aggressively so that it does not progress to sepsis or septic shock, which can lead to death even if treatment is initiated.

Prevention

Bacteremia can be prevented by preventing the infections that often precede it. Good personal hygiene such as effective hand-washing, especially during viral illness, may reduce the risk of developing bacterial infection. Treating bacterial infections quickly and thoroughly canminimize the risk of spreading infection. During medical procedures, the burden falls on medical professionals to minimize the number and duration of invasive procedures, to reduce patients' exposure to sources of bacteria when being treated, and to use scrupulous technique.