Bacteria Culture Test
Reviewed
Also called: Bacterial culture, Microbial culture
A bacteria culture test checks for a bacterial infection by growing bacteria from a sample in a lab. It identifies the type of bacteria causing the infection, which helps guide treatment.
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
Ask your healthcare provider if you need to do anything to prepare. Preparation depends on the type of sample needed.
A sample is collected from the suspected infection site. Common methods include: throat swab, urine collection, coughing up sputum, blood draw, stool sample, or wound swab. For deep wounds, a syringe or biopsy may be used.
The main limitation is that the test may not detect all bacterial infections (false-negative) if the sample does not contain enough bacteria or if the bacteria do not grow in culture. The test also requires time to grow bacteria (1–2 days, but some take longer). The sample collection methods are described by the source as having no known risks.
Understanding results
Results usually take 1–2 days, but some bacteria grow slowly and may take 5 days or longer. Your healthcare provider will interpret the results.
- Positive (harmful bacteria found): Harmful bacteria were detected. This usually means you have a bacterial infection. The test also identifies the type of bacteria causing the infection. Limitation: A positive result usually indicates infection, but your provider will correlate with your symptoms. The test requires enough bacteria to grow, which takes time. Next step: Your provider will discuss treatment options based on the bacteria type and may order an antibiotic sensitivity test to guide treatment. They may also order additional tests to confirm the diagnosis or assess severity.
- Negative (no harmful bacteria found): No disease-causing bacteria were grown from your sample. This may mean you do not have a bacterial infection, or the sample did not contain enough bacteria to grow (false-negative). Limitation: A negative result does not rule out infection. Some bacteria are difficult to culture or require special conditions, leading to a false-negative result. Next step: Your provider may consider other causes for your symptoms (e.g., viruses, fungi) or repeat the test with a different sample. Do not take antibiotics unless prescribed.
- 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).
- The sample collection methods (swab, blood draw, urine, sputum, stool, wound) are described by the source as having no known risks.
What to do next
If you have questions about your results, talk with your provider. If your results show you do not have a bacterial infection, do not take antibiotics—they only work against bacteria and can contribute to antibiotic resistance.
- 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?