Bacteria Culture Test
Reviewed
Also called: Bacterial culture, Microbial culture
A bacteria culture test can determine if you have a bacterial infection and, if so, which type of bacteria is causing it.
Specimen: Varies by infection site: blood, urine, sputum, stool, wound swab, throat swab, or other tissue
Why this test may be ordered
- You have symptoms of a bacterial infection (symptoms depend on the infection site).
- To identify the specific bacteria causing an infection.
- To help choose the most effective antibiotic (often combined with an antibiotic sensitivity test).
Preparation and collection
There are many different types of bacteria culture tests. Ask your provider if you need to do anything to prepare for your test.
To do a bacterial culture test, you will need to give a sample of your blood, urine, skin, or other tissue. The type of sample depends on where the infection is located.
There are no known risks to having a swab or blood test or to providing a urine, sputum, wound, or stool sample.
Understanding results
It normally takes one to two days to grow enough bacteria for the test. But some types of bacteria grow slowly, so sometimes your results may take several days or longer.
- Positive (harmful bacteria found): If harmful bacteria are found in your sample, it usually means you have a bacterial infection. The test should also identify what type of bacteria is causing the infection. Limitation: Your provider may order more tests to confirm the diagnosis or to see how serious the infection is. Next step: Your provider may also order a test to determine which medicine will best treat the type of bacteria causing your infection.
- Antibiotic sensitivity (susceptibility) test results: This test is called an antibiotic sensitivity test or a susceptibility test. It checks to see how sensitive the bacteria are to different antibiotic medicines. Limitation: Antibiotic resistance allows harmful bacteria to change in a way that makes antibiotics less effective or not effective at all. Next step: If you have questions about your results, talk with your provider.
- The test requires enough bacteria to grow, which takes time (1–2 days, but some bacteria grow slowly and may take 5 days or longer).
- A negative result does not completely rule out infection because some bacteria may not grow in culture (false-negative).
- Some types of bacteria grow slowly, so results may take several days or longer.
What to do next
If you have questions about your results, talk with your provider.
- What type of sample do I need to provide?
- How should I prepare for the test?
- When will I get my results?
- What do my results mean?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.