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Bacteremia

by Lowell S. Young, MD

Bacteremia is the presence of bacteria in the bloodstream (see also Occult Bacteremia).

  • Bacteremia may result from ordinary activities (such as toothbrushing), dental or medical procedures, or from infections (such as pneumonia or a urinary tract infection).

  • Having an artificial joint or heart valve or having heart valve abnormalities increases the risk that bacteremia will persist or cause problems.

  • Bacteremia usually causes no symptoms, but sometimes bacteria accumulate in certain tissues or organs and cause serious infections.

  • People at high risk of complications from bacteremia are given antibiotics before certain dental and medical procedures.

Usually, bacteremia, particularly if it occurs during ordinary activities, does not cause infections because bacteria typically are present only in small numbers and are rapidly removed from the bloodstream by the immune system. However, if bacteria are present long enough and in large enough numbers, particularly in people who have a weakened immune system, bacteremia can lead to other infections and sometimes trigger a serious bodywide response called sepsis.

Bacteria that are not removed by the immune system may accumulate in various places throughout the body, causing infections there, as in the following:

  • Tissues that cover the brain (meningitis)

  • The sac around the heart (pericarditis)

  • The cells lining the heart valves and the heart (endocarditis)

  • Bones (osteomyelitis)

  • Joints (infectious arthritis)

In bacteremia, bacteria tend to lodge and collect on structures, such as abnormal heart valves, and any artificial material present in the body, such as intravenous catheters and artificial (prosthetic) joints and heart valves. These collections (colonies) of bacteria may remain attached to the sites and continuously or periodically release bacteria into the bloodstream.

Causes

Ordinary activities sometimes cause bacteremia in healthy people. For example, vigorous toothbrushing can cause bacteremia because bacteria living on the gums around the teeth are forced into the bloodstream. Bacteria may also enter the bloodstream from the intestine during digestion. Bacteremia that occurs during ordinary activities rarely leads to infections.

Dental or medical procedures can lead to bacteremia. During dental procedures (as during tooth cleaning by a dental hygienist), bacteria living on the gums may become dislodged and enter the bloodstream. Bacteremia may also occur when catheters are inserted into the bladder or tubes are inserted into the digestive or urinary tract. Bacteria may be present at the site of insertion (such as the bladder or intestine). So even though sterile techniques are used, these procedures may move bacteria into the bloodstream. Surgical treatment of infected wounds, abscesses, and pressure sores can dislodge bacteria from the infected site, causing bacteremia.

In some bacterial infections, such as pneumonia and skin abscesses, bacteria may periodically enter the bloodstream, causing bacteremia. Many common childhood bacterial infections cause bacteremia.

Injecting recreational drugs can cause bacteremia because the needles used are usually contaminated with bacteria.

Symptoms and Diagnosis

Usually, bacteremia that results from ordinary events such as dental procedures causes no symptoms. Bacteremia due to other conditions sometimes causes fever. If people with bacteremia have a fever, a rapid heart rate, and rapid breathing, sepsis is likely.

If bacteremia is suspected, doctors usually do blood tests to try to grow (culture) the bacteria in the laboratory.

Prevention and Treatment

People who are at high risk of complications due to bacteremia (such as those who have an artificial heart valve or joint or certain heart valve abnormalities) are often given antibiotics before procedures that can cause bacteremia:

  • Dental procedures

  • Surgical treatment of infected wounds

  • Insertion of bladder catheters

Antibiotics help prevent bacteremia and thus infections and sepsis from developing.

If an infection or sepsis develops, it is treated.