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 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 sensitivity testing.
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 pneumonia or 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 sputum.
- Identify the best antibiotic to treat the infection (sensitivity testing).
- Monitor treatment of an infection.
INSTRUCTIONS FOR COLLECTING SPUTUM FOR TB (TUBERCULOSIS)
WHY IS A SPUTUM TEST NECESSARY?
Your doctor wants to collect some of the sputum (“phlegm”) that you cough up from your lungs. The laboratory will test the sputum for tuberculosis (TB) germs.
Checking your sputum is the best way to find out if you have TB disease. If you are already taking medicine for TB, checking your sputum is the best way to tell if the medicine is working.
To be sure the test is accurate, you must cough up sputum from deep inside your lungs. Sputum from your lungs is usually thick and sticky. Saliva comes from your mouth and is watery and thin. Do not collect saliva.
HOW TO COLLECT A SPUTUM SAMPLE
Your doctor or nurse will give you a special plastic cup for collecting your sputum. Follow these steps carefully:
- The cup is very clean. Don’t open it until you are ready to use it.
- As soon as you wake up in the morning (before you eat or drink anything), brush your teeth and rinse your mouth with water. Do not use mouthwash.
- If possible, go outside or open a window before collecting the sputum sample. This helps protect other people from TB germs when you cough.
- Take a very deep breath and hold the air for 5 seconds. Slowly breathe out. Take another deep breath and cough hard until some sputum comes up into your mouth.
- Spit the sputum into the plastic cup.
- Keep doing this until the sputum reaches the 5 ml line (or more) on the plastic cup. This is about 1 teaspoon of sputum.
- Screw the cap on the cup tightly so it doesn’t leak.
- Wash and dry the outside of the cup.
- Write on the cup the date you collected the sputum.
- Put the cup into the box or bag the nurse gave you.
- Give the cup to your clinic or nurse. You can store the cup in the refrigerator overnight if necessary. Do not put it in the freezer or leave it at room temperature.
Your throat may feel sore following bronchoscopy or collection of a sputum sample using a nasotracheal catheter.
If you have severe asthma or bronchitis, you may find it hard to breathe during collection of a sputum sample using a nasotracheal catheter.
A sputum culture is a test to detect and identify bacteria or fungi that are infecting the lungs or breathing passages. Some types of bacteria or fungi grow quickly in a culture and some grow slowly. Test results may take from one day to several weeks, depending on the type of infection suspected. Some organisms (such as Chlamydophila pneumoniae and mycoplasma) do not grow in a standard culture and need a special growth medium to be detected in a sputum culture.If test results point to an infection, sensitivity testing may be done to determine the best antibiotic to kill the bacteria or fungus.