Harmful microbes such as fungi, bacteria or viruses can cause blood infections in our bodies. In blood infections, your immune system releases a lot of chemicals in your blood. It makes the fight against the infection difficult for the immune system. The infection can be severe, causing a lot of health complications.

A blood culture detects the infection in the blood. It also determines the presence of bacteria, fungi or viruses in the blood. If the bacteria are present in the blood, this condition is called bacteremia. And if fungi like yeast are present in the blood, this condition is called fungemia. Your doctor recommends a blood culture test every two or four days to measure the severity of the infection.

You may need a blood culture test when experiencing symptoms like high fever, nausea, vomiting, chills, less frequent urination, dizziness, excessive fatigue, increased pulse rate, etc. The bacteria, fungi or viruses in the blood can cause mild to severe health complications, such as sepsis, septic shock and sudden organ failure.

Studies suggest that about 28% of people in India are diagnosed with sepsis or severe blood infections. Among them, around 20% of the patients need to be hospitalised and they require blood cultures.

Other names for a blood culture test

• Fungal blood culture test
• Blood culture and sensitivity test
• Blood C&S test
• Bacterial blood culture test

What does the blood culture test measure/ and who is this prescribed for?

A blood culture test detects the presence of infection and microorganisms such as bacteria, fungi and viruses. The positive presence of bacteria in the blood can cause a severe blood infection, leading to other health complications.

A doctor may recommend you a blood culture test if you have symptoms, such as:

• Increased heart rate
• Muscles pain
• Severe headache
• Difficulty in breathing
• Low or high fever
• Decreased urine excretion
• Dizziness
• Nausea and vomiting
• Excessive fatigue
• Mental confusion
• Rapid chills

If the infection becomes more severe, then it can lead to sepsis. In this case, you may develop much more severe symptoms, such as:

• Frequent drops in blood pressure
• Sudden Failure of one or more organs of the body
• Inflammation all over the body
• Formation of many tiny blood clots in all of the body's smallest blood vessels

A doctor may recommend you for a blood culture test when diagnosed with diabetes, cancer, an autoimmune disease or sexually transmitted diseases like HIV or AIDS.

When a blood culture test is positive or you have symptoms of blood infection, you need to seek treatment. Consult a specialist in emergency medicine. Your doctor may prescribe you medicines according to your condition.

A blood sample is needed to undergo a blood culture test. No other specific preparation is required for the test.

Test Preparation

For the blood culture test, you do not require any specific preparation. The blood sample is collected by drawing away blood from one of the veins present in your arm.

Usually, two samples are collected from two different veins to detect bacteria or fungi in the blood. Collected samples are put in two culture bottles, which contain preventatives to inhibit the growth of microbes.

After collection, the bottles are sent to the laboratory for analysis. The procedure is simple and does not have any risk to your health.

What are the parameters included in the test?

The blood culture test measures the presence of an infection in the blood. It also confirms the presence of bacteria, fungi or viruses in the blood.

The positive presence can affect your health, causing a severe infection of the blood like septicemia. At the same time, the negative presence cannot affect your health.

How frequently should you take this test?

A doctor may recommend a blood culture test to check the presence of infection. With positive blood culture test results, a repeat test within two or four days is recommended by the doctor. The doctor may advise repeating the test within three to six months if you have recurrent symptoms of a blood infection.

Sepsis, Blood infection, Septic shock, Acute respiratory distress syndrome (ARDS)

The blood culture test determines infection in the blood. The test is usually taken with two or more blood samples to detect the presence of fungi or bacteria. Multiple blood samples identify true pathogens.

• If two or more blood cultures are favourable for the same bacteria or fungi, the person tested likely has a blood infection with that organism. The results help identify the fungi or bacteria causing the infection.

• If one blood culture set is positive and one set is negative, it may mean that an infection or skin contaminant is present. Additional tests are done in such cases.

• If blood culture sets are negative after several days (no growth), then the probability of a blood infection caused by bacteria or fungi is low.

The blood culture test result is interpreted as positive/abnormal or negative/normal.

• Abnormal or positive means the presence of bacteria or fungi in the bloodstream. It can cause severe health complications.
• A normal or negative result means no detection of bacteria or fungi in the bloodstream.

Positive blood culture test: The positive results of the blood culture test show a severe blood infection which can further lead to health problems like:

• Sepsis: A condition in which infection can lead to abnormal functioning of the body’s immune system. People with diseases for a long time are at a higher risk of sepsis because they already have a weakened immune system.

• Septic shock: Septic shock is a medical condition in which a patient feels a severe drop in blood pressure. In sepsis, some toxic chemicals are released by the bacteria in the bloodstream. They lead to poor blood flow, resulting in organ damage. Septic shock is a medical emergency.

• Acute respiratory distress syndrome (ARDS): A condition in which fluid collects in the lungs, which leads to poor oxygen supply to organs. ARDS occurs in people with severe blood infections and low immune response.

• Sudden Organ failure: A condition in a patient with sepsis in which an essential system or organ in the body fails to do its regular work suddenly. Some expected consequences which can occur during sepsis are heart failure or kidney failure.

Negative blood culture test: The negative blood culture test shows no bacteria or fungi in the blood. No detection of bacteria or fungi means no blood infection in your body.