A sputum culture is a test to detect and identify bacteria or fungi (plural of fungus) that are infecting the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the airways leading to the lungs. A sample of sputum is placed in a container with substances that promote the growth of bacteria or fungi. If no bacteria or fungi grow, the culture is negative. If organisms that can cause infection grow, the culture is positive. The type of bacterium or fungus will be identified with a microscope or by chemical tests.
If bacteria or fungi that can cause infection grow in the culture, other tests may be done to determine which antibiotic will be most effective in treating the infection. This is called susceptibility or sensitivity testing.
This test is done on a sample of sputum that is usually collected by coughing. For people who can't cough deeply enough to produce a sample, they can breathe in a mist solution to help them cough.
Why It Is Done
A sputum culture is done to:
- Find and identify bacteria or fungi that are causing an infection (such as pneumonia or tuberculosis) of the lungs or the airways leading to the lungs. Symptoms of a lung infection may include difficulty breathing, pain when breathing, or a cough that produces bloody or greenish brown sputum.
- Identify the best antibiotic to treat the infection (sensitivity testing).
- Monitor treatment of an infection.
How To Prepare
Do not use mouthwash before collecting a sputum sample because it may contain antibacterial substances that could affect your results.
If bronchoscopy will be used to collect your sputum sample, your doctor will tell you how soon before the test to stop eating and drinking. Follow the instructions exactly about when to stop eating and drinking, or your surgery may be canceled. If your doctor has instructed you to take your medicines on the day of surgery, please do so using only a sip of water.
Tell your doctor if you have recently taken any antibiotics.