Patient education: Sputum culture (The Basics)

What is a sputum culture? — 

This is a lab test to check a sample of sputum for bacteria and other germs. Sputum is mucus that is coughed up from the lungs.

Most of the time, sputum is collected when you cough. Sometimes, doctors will do a procedure called a "bronchoscopy" to get sputum from your lungs.

For a sputum culture, a sample of the sputum is sent to a lab. In the lab, they add a special substance that makes germs grow. If there are germs in the sputum, these will show up within a few days.

Why might I get a sputum culture? — 

Your doctor might order a sputum culture to:

●Find out the exact germ causing a lung infection

●Help decide what antibiotics to prescribe – A culture can show what kind of bacteria are causing an infection. This is important for deciding how to treat it.

How do I prepare for a sputum culture? — 

If you are having a bronchoscopy, the doctor or nurse will tell you if you need to do anything special to prepare.

If you need to cough up sputum, try to give the sample early in the morning before you:

●Eat or drink anything

●Brush your teeth or dentures

●Use mouthwash

●Smoke

You might be asked to:

●Rinse your mouth with water before starting

●Breathe in an aerosol mist or medicine to help loosen the sputum in your lungs

How do I collect sputum? — 

The staff will give you a special container to cough into. To cough up a sputum sample:

●Take a deep breath, and hold it for a few seconds. Breathe out.

●Take another deep breath, and cough to bring up sputum from deep in your lungs. You might need to repeat this a few times to bring up enough sputum for the test.

●Spit the sputum into the container, and screw the lid on tight.

Give your sputum sample to the staff.

What do my results mean? — 

Your doctor or nurse will tell you when to expect your results, and will use them to guide any treatment you might need. Or if you use an online "patient portal," you might get an alert there when your results are ready.

●If your sputum culture is "normal," this means you do not have harmful bacteria or other germs in your sputum. You might have bacteria or germs in your sputum that are normally found in your throat or airways. This does not necessarily mean they are causing an infection that needs treatment.

●If your sputum culture is " abnormal," this means you do have bacteria or other germs in your sputum that could be causing your symptoms. Your doctor or nurse will talk to you about what to do next and whether you need treatment. If you have a bacterial infection, your doctor will prescribe an antibiotic to treat it.

How accurate is a sputum culture? — 

A sputum culture can be a helpful tool, but it is not always accurate. In some cases, it does not have enough germs in it to give a positive result. The culture can also show germs that normally live in the airways or throat. These are likely not what is causing symptoms.

More on this topic

Patient education: Diagnostic bronchoscopy (The Basics)
Patient education: Pneumonia in adults (The Basics)
Patient education: Pneumonia in children (The Basics)
Patient education: Tuberculosis (The Basics)
Patient education: Cystic fibrosis (The Basics)
Patient education: What you should know about antibiotics (The Basics)

Patient education: Flexible bronchoscopy (Beyond the Basics)
Patient education: Pneumonia in adults (Beyond the Basics)
Patient education: Tuberculosis (Beyond the Basics)