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Lung Disease & Respiratory Health Center

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Sputum Culture

How It Is Done continued...

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 medicine 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.

Suction

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.

After a sample is collected

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 more days.

How It Feels

If you have discomfort when taking a deep breath or when coughing, obtaining a sputum sample may be uncomfortable. If you need to inhale the aerosol mist to produce a sputum sample, you will often feel a deep, uncontrollable urge to cough.

During bronchoscopy or collection of a sputum sample using a catheter, you may feel a strong urge to cough as the bronchoscope or catheter passes into the back of your throat. You may also feel as if you cannot breathe. Try to relax and breathe slowly while the bronchoscope or catheter is in place. If you are given medicine to numb your throat and nose, you may feel as if your tongue and throat are swollen and that you cannot swallow.

Risks

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.

Results

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.

Sputum culture
Normal:

Sputum that has passed through the mouth normally contains several types of harmless bacteria, including some types of strep (Streptococcus) and staph (Staphylococcus). The culture should not show any harmful bacteria or fungi. Normal culture results are negative.

Abnormal:

Harmful bacteria or fungi are present. The most common harmful bacteria in a sputum culture are those that can cause bronchitis, pneumonia, or tuberculosis. If harmful bacteria or fungi grow, the culture is positive.

If test results point to an infection, sensitivity testing may be done to determine the best antibiotic to kill the bacteria or fungus.

WebMD Medical Reference from Healthwise

Last Updated: November 01, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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