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Sputum Culture
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 (pathogenic organisms) 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 cannot 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:
- Detect 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. In most cases, you will need to stop eating at least 6 hours before your test. You may be able to drink clear liquids, such as water, coffee, or tea, up to 2 hours before the test. But be sure to follow the exact instructions your doctor gives you.
Tell your health professional if you have recently taken any antibiotics.
How It Is Done
Usually, the sputum sample is collected early in the morning before you eat or drink anything. In some cases (especially if you may have tuberculosis), three or more morning samples may be needed.
If you wear dentures, you will need to remove them before collecting a sputum sample. Then rinse your mouth with water, take a deep breath, and then cough deeply to produce a sample of sputum. The health professional collecting the sample may tap on your chest to help loosen the sputum in your lungs before you cough. If you still have trouble coughing up a sample, you may be asked to inhale an aerosol mist to help you cough.
WebMD Medical Reference from Healthwise
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