Sputum Culture

A sputum culture is a test that checks for bacteria or another type of germ that may be causing a respiratory tract infection (an infection in your lungs or airways). Sputum, also known as phlegm, is a thick type of mucus made in your lungs. If you have an infection or chronic illness affecting the lungs or airways, sputum can settle in your lungs, and you may also cough it up Sputum is not the same as spit or saliva.

Sputum contains cells from your immune system that help fight bacteria, fungi, or other foreign substances in your lungs or airways. The thickness of sputum helps trap the foreign material. This allows cilia (tiny hairs) in the airways to push it through the mouth and be coughed out.

Sputum can be one of several different colors. The colors can help identify the type of infection you may have or check if a chronic illness has become worse. This helps your health care provider determine the best treatment.

Sputum colors can include: Clear. This usually means you don't have an infection, but large amounts of clear sputum may be a sign of lung disease.; White or gray. This may also be normal, but increased amounts may mean lung disease.; Dark yellow or green.

This often means a bacterial infection, such as pneumonia. Yellowish-green sputum is also common in people with cystic fibrosis. Cystic fibrosis is an inherited disease that causes mucus to build up in the lungs and other organs.; Black.

This often shows up in people who smoke. It is also a common sign of black lung disease. Black lung disease is a serious condition that can happen if you have long-term exposure to coal dust.; Brown or brown spots.

This may be a sign of old blood. This can happen if you have cystic fibrosis, bacterial pneumonia, bacterial bronchitis, or some other lung diseases. It can also be caused by breathing in dust or other brown materials or toxins. ; Pink.

This may be a sign of pulmonary edema, a condition in which excess fluid builds up in the lungs. Pulmonary edema is common in people with heart failure.; Red. This may be an early sign of lung cancer.

It may also be a sign of a pulmonary embolism (PE), a life-threatening condition in which a blood clot from a leg or other part of the body breaks loose and travels to the lungs. If you are coughing up red or bloody sputum, call 911 or seek immediate medical attention.;

Why this test is done

You may need this test if you have symptoms of pneumonia or another serious infection of the lungs or airways. These include:

• Cough which produces a lot of sputum
• Fever
• Chills
• Shortness of breath
• Chest pain that gets worse when you breathe deeply or cough
• Fatigue
• Confusion, especially in older people

Your provider may also order a sputum culture after an x-ray or other imaging tests show that you may have a lung infection. The sputum culture can help confirm this and determine the cause of the infection.

How to prepare

The test is often scheduled in the morning. To increase the amount of sputum, you may be encouraged to drink more water the night prior. You may also be asked not to eat for one or two hours before the test.

If you will be getting a bronchoscopy, you may be asked to fast (not eat or drink) for up to twelve hours before the test.

You may need to stop taking certain medicines before this test, so tell your provider about everything you take. Antibiotics may affect bacterial growth and the results of your sputum culture test. But don't stop taking any medicines unless your provider tells you to.

Other names for this test

respiratory culture, bacterial sputum culture, routine sputum culture, bacterial culture, respiratory