Routine Sputum Culture

Definition

Routine sputum culture is a test of secretions from the lungs and bronchi (tubes that carry air to the lung) to look for organisms that cause infection.

Alternative Names

Sputum culture

How the test is performed

A health care provider will often collect sputum samples in the morning. The doctor or nurse may have you rinse your mouth first. The goal is to bring sputum up from deeper in your airways and your throat.

You will be asked to take three deep breaths, then force up some sputum amount by coughing deeply. You will spit any sputum that comes up into a sterile cup. The sputum is then taken to the laboratory. There, it is placed in a special substance (medium) under conditions that allow the bacteria or fungi to grow.

How to prepare for the test

Drinking a lot of water and other fluids the night before the test may help to get the sample.

How the test will feel

You will need to cough. Sometimes the health care provider will tap on your chest to loosen deep sputum. There may be a steam-like mist to inhale to help you cough up the sample.

Why the test is performed

The culture is done on the sputum to help identify the bacteria, or other type of germs, that are causing an infection in the lungs or airways (bronchi). The doctor may collect a sputum sample the office or in the hospital.

The culture can prevent the need for more invasive procedures such as bronchoscopy.

Normal Values

In a normal sputum sample there will be no disease-causing organisms present. Often, bacteria that normally live in the mouth will grow in a sputum culture. This does not mean that you have a lung or airway infection.

What abnormal results mean

If the sputum sample is abnormal, the results are called "positive." Identifying the bacteria, fungus, or virus may help diagnose the cause of:

  • Bronchitis
  • Lung abscess
  • Pneumonia
  • Tuberculosis
  • Flare up of chronic obstructive pulmonary disease or cystic fibrosis

What the risks are

There are no risks with this method of obtaining a sample, although severe coughing might cause some chest discomfort.

Special considerations

Sometimes a Gram stain or acid fast bacilli (AFB) stain of the sputum done at the same time can help make the diagnosis.

References

Limper AH. Overview of pneumonia.In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed.Philadelphia,PA: Saunders Elsevier; 2011:chap 97.

Torres A, Menendez R, Wunderink R. Pyogenic bacterial pneumonia and lung abscess. In: Mason RJ, Broaddus VC, Martin TR, et al, eds.Murray and Nadel’s Textbook of Respiratory Medicine. 5th ed.Philadelphia,Pa: Saunders Elsevier; 2010:chap 32.

Review Date: 12/12/2011

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright ©2003 A.D.A.M., Inc., as modified by University of California San Francisco. Any duplication or distribution of the information contained herein is strictly prohibited.

Information developed by A.D.A.M., Inc. regarding tests and test results may not directly correspond with information provided by UCSF Medical Center. Please discuss with your doctor any questions or concerns you may have.