Bacteria Culture Test
What is a bacteria culture test?
Bacteria are simple, single-cell organisms that were among the first forms of life on Earth. They live all around us and inside us. Most bacteria are harmless or even beneficial, but some can cause diseases and associated symptoms. In fact, bacteria cause most infectious diseases.
A bacteria culture is a test to confirm whether you have a bacterial infection. The test can also identify what type of bacteria caused the infection. It can also help healthcare providers choose the most effective treatment because certain antibiotics are more effective against specific bacteria.
When is a bacteria culture test performed?
A bacteria culture test is a common tool. A healthcare provider uses the test when a person has symptoms of a bacterial infection, such as:
- Food poisoning.
- Kidney infection.
- Strep throat.
- Urinary tract infection.
- Wound infection in a cut or burn.
Who orders a bacteria culture test?
Various healthcare providers may order the test and collect the sample to send to a lab, including:
How does the test work?
For a bacteria culture test, a healthcare provider takes a small sample of a substance from your body. The sample area depends on what symptoms you have and what infection your healthcare provider suspects.
The provider sends the sample to a laboratory. At the lab, experts use special techniques to deliberately encourage any micro-organisms in the sample to grow and multiply. Then they examine the sample under a microscope to identify bacteria or yeast.
What are the different types of bacterial culture tests?
Bacteria can be sampled from various areas of your body or substances inside your body, depending on the type of infection suspected. The different types are:
- Blood culture: A blood culture checks for systemic infection throughout your entire body, such as sepsis. A healthcare provider collects the blood sample from a vein, usually in your arm. Blood cultures are rarely done on outpatients and should be repeated at regular intervals.
- Cerebrospinal (CSF) fluid culture: A CSF culture tests a sample of the fluid that protects the spine. A healthcare provider inserts a needle into a space between two vertebrae in your spine to get the sample. This procedure is called a spinal tap (lumbar puncture).
- Stool culture: A stool culture tests poop for an infection in your digestive tract. A healthcare provider will ask you to poop into a sterile cup that is then sealed and sent to a lab.
- Throat culture: A throat culture tests for infection in your throat like strep throat. A healthcare provider swabs the back of your throat for a sample of cells.
- Sputum culture: If your provider suspects an infection deep in your lungs, they may run tests on sputum. Sputum is a thick mucus that comes from deep in your lungs. It’s also called phlegm. A healthcare provider will ask you to cough up sputum.
- Urine culture: A urine culture tests pee to help diagnose infection in the urinary tract, including the kidneys. A healthcare provider will ask you to clean your genitals then pee directly into a small, sterile cup. The cup is then sealed and sent to the lab. In the hospital, a urine sample may be collected through a catheter. A catheter is a thin tube inserted into the urethra (the tube where urine exits the body).
- Wound culture: If you have a cut or burn that might be infected, you may need a wound culture, also called a skin culture. A healthcare provider will use a syringe to take a sample of fluid or pus from the wound, or a piece of tissue is sent to the lab.
How do I prepare for a bacterial culture test?
Most bacteria culture tests don’t require any preparation. But ask your healthcare provider whether there are any special instructions.
What are the risks of this test?
Bacteria culture tests have a very low risk of any complications. Most have no known risks. Blood and CSF cultures involve a small chance of infection or bleeding because those tests involve a needle puncture in the skin. A CSF culture is usually done on someone who is critically ill or likely to become critically ill in the near future.
Results and Follow-Up
When will I know the results of the bacterial culture test?
After the sample goes to the lab, lab staff use specific techniques to make the cells multiply and grow. This gives experts enough bacterial cells to examine under a microscope or test for specific chemical reactions, including susceptibility to various antibiotics. The process takes one to five days, depending on the type of bacteria.
If the sample contains enough bacteria, the lab confirms an infection. The lab will tell the healthcare provider what type(s) of bacteria were found.
The lab also might run antimicrobial susceptibility testing (AST). AST is a lab test that identifies which treatment regimen would be most effective against the type of infection you have. After getting these results your provider may determine that a different antibiotic would work better than one initially prescribed because certain antibiotics are more effective against specific bacteria.
A note from Cleveland Clinic
A bacteria culture is a test to identify whether you have a bacterial infection. It can be performed on a sample of blood, stool, urine, skin, mucus or spinal fluid. Using this type of test, a healthcare provider can identify what caused an infection and determine the most effective treatment.
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