Sputum Culture

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.

Some people may need bronchoscopy to collect a sputum sample. During bronchoscopy, a thin, lighted tube (bronchoscope) is inserted through your mouth or nose into the airways leading to your lungs. You will be given medication that numbs your throat and nose so you do not feel discomfort from the bronchoscope. You may also be given a sedative to make you sleepy during the procedure. To collect the sputum sample, a salt solution may be washed into the airway and then suctioned into a container. A small, thin brush may be used to collect a sample.

A sputum sample can also be collected using suction. During this procedure, a soft, flexible tube (called a nasotracheal catheter) is inserted through the nose and down the throat. Suction is applied for up to 15 seconds to collect the sputum sample. This method of collecting a sputum sample is often used for people who are very sick or unconscious.

In rare cases, a sputum sample may need to be collected by inserting a needle through the neck into the windpipe (trachea). This is called a transtracheal aspiration. Before a transtracheal aspiration, a local anesthetic is injected into the site where the needle will be inserted. Oxygen may be used before and after a transtracheal aspiration to aid breathing. This method of collecting a sputum sample may be used for people who are very sick and in the hospital.

Once the sputum sample is collected, it will be placed in a container with substances (growth medium or culture medium) that promote the growth of infecting organisms (bacteria or fungi). Bacteria usually need 2 to 3 days to grow; fungus often takes a week or longer to grow. The organism that causes tuberculosis may take 6 weeks to grow. Any bacteria or fungi that grow will be identified under a microscope or by chemical tests. Sensitivity testing, to determine the best antibiotic to use against the organism that grows, often takes 1 to 2 additional days.

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Author:	Monica Rhodes	Last Updated: March 10, 2009
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care, Medical Toxicology
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