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
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
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
- Identify the best
antibiotic to treat the infection (sensitivity
- 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
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.
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
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.