Section 17. Infections

Chapter 191. Bacteremia, Sepsis, and Septic Shock

Topics: Introduction | Bacteremia and Sepsis | Septic Shock

Bacteremia and Sepsis

Bacteremia is the presence of bacteria in the bloodstream; sepsis is a bacterial infection in the bloodstream.

Temporary bacteremia may occur during dental procedures or toothbrushing, because bacteria living on the gums around the teeth are forced into the bloodstream. Bacteria may also enter the bloodstream from the intestine, but they are rapidly removed when the blood passes through the liver. These conditions are usually not serious.

Sepsis is less common. It most often occurs when there is another infection somewhere within the body, such as in the lungs, abdomen, urinary tract, or skin. Although bacteria typically stay at the original site of infection, they sometimes spread into the bloodstream. Sepsis can also result when surgery is performed on an infected area or on a part of the body where bacteria normally grow, such as the intestine. The presence of a foreign object--such as an intravenous line, urinary catheter, drainage tube, prosthetic joint, or artificial heart valve--may increase the risk of sepsis. The likelihood of sepsis increases the longer the object is left in place. Sepsis is more common in injecting drug users, who rarely use sterile drugs and needles. It is also more likely to occur in a person whose immune system is not functioning properly--for example, a person receiving chemotherapy. Rarely, nonbacterial infections can cause sepsis.

The circulating bacteria may settle in sites throughout the body if treatment is not given quickly. An infection can develop in the tissues surrounding the brain (meningitis), the sac around the heart (pericarditis), the inside lining of the heart (endocarditis), the bones (osteomyelitis), the joints (infectious arthritis), and other areas. Certain types of bacteria, such as staphylococci, may produce abscesses (collections of pus) in the organs they infect.

Symptoms and Diagnosis

Because the body is usually able to clear small numbers of bacteria quickly, temporary bacteremia rarely causes symptoms. Symptoms such as shaking, chills, fever, weakness, confusion, nausea, vomiting, and diarrhea indicate sepsis. Depending on the type and location of the initial infection (if any), other symptoms may also be present.

A doctor usually suspects sepsis when a person who has an infection suddenly develops a high fever. Bacteria in the bloodstream are usually difficult to detect directly. To make the diagnosis, a doctor takes several blood samples to try to grow the bacteria in the laboratory (blood culture)--a process that takes 1 to 3 days. However, bacteria may not always grow in a blood culture, particularly if the person is taking antibiotics. Cultures from other fluids and substances--for example, urine, cerebrospinal fluid, tissue from wounds, and material coughed up from the lungs (sputum)--may also be analyzed for the presence of bacteria. Sometimes catheters are removed from the body and the tips are cut off and sent for culture.

Treatment and Prognosis

Bacteremia caused by surgery or dental procedures usually requires no treatment. Bacteremia caused by insertion of a catheter (catheterization) into the urinary tract may not require treatment, as long as the catheter is removed quickly. However, to prevent bacteremia and sepsis, people at risk of developing serious infections (such as those with heart valve disease or a weakened immune system) generally are given antibiotics before undergoing such procedures.

Sepsis is very serious, and the risk of death is high. Sepsis requires immediate treatment with antibiotics--even if test results confirming the diagnosis are not yet available. A delay in starting antibiotic treatment greatly decreases the person's chances of survival. Initially, a doctor bases the choice of antibiotic on which bacteria are most likely to be present, which depends on where the infection started. Often, two or three antibiotics are given together to increase the chances of killing the bacteria, particularly when the source of the bacteria is unknown. Later, when the test results are available, the doctor can substitute the antibiotic that is most effective against the specific bacteria causing the infection. Surgery may sometimes be needed to eliminate the source of the infection.

The drug drotrecogin alfa (activated), an artificially produced human protein that prevents inflammation and blood clotting, may improve survival in people with severe sepsis.