Sputum Culture

What Is a Sputum Culture?

A sputum culture is a test that looks mainly for bacteria but can be helpful with other infectious germs such as fungi from the phlegm that is produced in your lungs or airways usually during an active infection.

Sputum, the medical word for phlegm, is the thick mucus made in your lungs and airways. It is different from saliva, which is produced within the salivary glands of the mouth. Sputum is part of our body’s natural defense system against infections, helping trap and fight germs in your lungs and airways.

What to Expect?

To perform a sputum culture, your healthcare provider will ask you to provide a sample of sputum from deep in your lungs. This is usually a simple, non-invasive test. You may be asked to:

• Collect the sample early in the morning, before you eat or drink anything.
• Remove dentures, if you wear them, and rinse your mouth with water first.
• Take a deep breath and cough deeply to bring up sputum, not saliva.
• Spit the sputum into the sterile container provided by your healthcare provider.
• Provide more than one sample over several days, if needed.

If You Cannot Cough Up a Sputum Sample

If you are unable to produce enough sputum on your own, your provider may recommend a procedure called sputum induction. This helps to loosen and thin your sputum so it can be collected more easily. Sputum induction may involve:

• Completing the procedure in a healthcare setting.
• Avoiding food and liquids for at least 2 hours beforehand.
• Breathing in a mist (nebulized solution) that thins and loosens mucus.
• Coughing deeply to produce a sputum sample.

If sputum still cannot be collected, your provider may recommend a bronchoscopy. During this procedure:

• Your throat and nose are numbed to prevent discomfort, and you may also be given sedation or anesthesia.
• A thin, flexible tube, called a bronchoscope, is gently passed through your mouth or nose into your airways leading to your lungs.
• A sputum sample is collected from your lungs.

Understanding the Results

Results of a sputum culture are dependent on many factors such as quality, quantity and previous treatment with antibiotics. Sometimes a sample that appears ‘good’ may not show bacteria even with an active infection. When growth of a germ is noted, your provider will be able to explain the findings with you and discuss a treatment plan based on the type of germ found, which medications are indicated and your overall health needs.

What Are the Risks?

The risks depend on how the sputum sample is collected:

• A sputum test completed without assistance (coughing up a sample yourself) has very few risks. Some people may experience slight discomfort from repeated coughing.
• Sputum induction may trigger bronchospasm, a sudden tightening of the airway muscles, especially in people living with asthma or COPD. If this happens, it can be treated promptly with a bronchodilator.
• Bronchoscopy carries additional risks, such as a drop in oxygen levels during the procedure due to sedation or the bronchoscope in the airways. You may receive extra oxygen during the procedure. Because the bronchoscope passes through the vocal cords, coughing during and after the procedure is common. Your throat may also feel sore or irritated for a few days afterward.