Sputum Culture
Reviewed
Also called: respiratory culture, bacterial sputum culture, routine sputum culture, bacterial culture
A sputum culture is a test that checks for bacteria or another type of germ that may be causing a respiratory tract infection (an infection in your lungs or airways).
Specimen: Sputum (phlegm, not saliva)
Urgent safety information
If you are coughing up red or bloody sputum, call 911 or seek immediate medical attention.
Emergency numbers on this page are for the United States. Outside the US, call your local emergency number.
Why this test may be ordered
- Find and diagnose bacteria or fungi causing a lung or airway infection
- See if a chronic lung illness has worsened
- Check if treatment for a lung infection is working
- Help diagnose respiratory conditions such as pneumonia, tuberculosis, and bronchiectasis
Preparation and collection
The test is often scheduled in the morning. To increase the amount of sputum, you may be encouraged to drink more water the night prior. You may also be asked not to eat for one or two hours before the test. You may need to stop taking certain medicines before this test, so tell your provider about everything you take. Antibiotics may affect bacterial growth and the results of your sputum culture test. But don't stop taking any medicines unless your provider tells you to.
Your provider will need to get a sample of your sputum. Your provider will ask you to breathe deeply and then cough deeply into a special cup. If you still can't cough up enough sputum, your provider may perform a procedure called a bronchoscopy.
There is no risk to providing a sputum sample into a container. If you had a bronchoscopy, your throat may feel sore after the procedure. You will not be permitted to eat or drink until you can cough normally again.
Understanding results
It usually takes a few days to get the results of your sputum culture, but it may take weeks.
- Normal: If your results were normal, it means that no harmful bacteria or fungi were found. Limitation: Antibiotics may affect bacterial growth and the results of your sputum culture test. Next step: If you have questions about your results, talk to your provider.
- Abnormal: If your results were not normal, it may mean you have some kind of bacterial or fungal infection. The most common types of harmful bacteria found in a sputum culture include those that cause: Pneumonia, Bronchitis, Tuberculosis. Limitation: An abnormal sputum culture result may also mean a flare-up of a chronic condition, such as cystic fibrosis or chronic obstructive pulmonary disease (COPD). Next step: Your provider may need to do more tests to find the specific type of infection you have.
- Antibiotics may affect bacterial growth and test results.
- Results may take a few days to weeks depending on the type of bacteria being tested.
- This test is not usually used for viral infections.
What to do next
To understand the results of your sputum culture, your provider will consider your symptoms, medical history, and the results of other tests.
- What do my sputum culture results mean in combination with my symptoms?
- Do I need any other tests to confirm the diagnosis?
- Should I stop taking any of my medicines before this test?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.