Blood culture

What is a Blood Culture?

A blood culture is a test that helps detect bacterial or fungal infections in the blood. During a blood culture, a small sample of blood is taken from a vein in the arm and is placed into a sterile container. The blood is then cultured in the laboratory in order to detect any organisms that may be present in the blood which could potentially cause an infection.

Why is a Blood Culture Done?

A blood culture is used to detect and identify any microorganisms that are present in the blood. This may be done in order to diagnose a systemic infection or to monitor the effectiveness of an antibiotic treatment. In some cases, a blood culture may be used to detect organisms that are causing septicemia, a blood infection.

Preparation for a Blood Culture Test

No special preparation is required before the blood culture test. Patients may want to wear clothing that allows easy access to their arm for the phlebotomist to take the sample.

Procedure for a Blood Culture

  • The patient’s arm is prepared with antiseptic to reduce the risk of contamination.
  • A needle is inserted into the vein in the arm and blood is drawn into a sterile tube.
  • The drawn blood is allowed to clot and placed in a sterile container.

Types of Blood Cultures

The two types of blood culture tests are aerobic and anaerobic. Aerobic cultures look for bacteria which need oxygen to survive while anaerobic cultures look for bacteria that don't need oxygen to survive. Depending on the patient’s symptoms, a doctor may order one or both tests.

Risks of a Blood Culture

The risk of complications with a blood culture test are very low, but there is a small risk of bleeding or bruising at the puncture site. Additionally, there is a risk of the sample contamination. However, this risk can be reduced by using antiseptic on the patient's skin before taking the sample. .

When is a Blood Culture Needed

A blood culture is usually done if a doctor suspects that a bacterial or fungal infection is present. Blood cultures may also be done to check the effectiveness of an antibiotic treatment. In some cases, a doctor may order a blood culture if a patient has a fever of an unknown origin.