MedlinePlus Medical Encyclopedia: Sputum Gram stain

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Sputum Gram stain

Contents of this page:
Illustrations Alternative names Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Illustrations

Sputum test

Alternative names Return to top

Gram stain of sputum

Definition Return to top

Gram stain is a method of staining microorganisms (bacteria) using a special series of stains. In this test, a sputum specimen is examined under the microscope. Sputum is the mucous secretions produced by the lower respiratory tract (in the lungs).

The Gram stain method can be applied to almost any clinical specimen, and is one of the most commonly used techniques for the rapid diagnosis of bacterial infections.

How the test is performed Return to top

A sample of sputum is applied in a very thin layer to a microscope slide -- this is called a smear. A series of stains called a Gram stain is applied to the specimen. It is first stained with crystal violet stain, then iodine, then decolorized, then stained with safranin.

The stained smear is then examined under the microscope for the presence of bacteria. The color, size, and morphologic appearance (shape) of the cells help identify the infecting organism.

How to prepare for the test Return to top

You will produce a sputum sample from your lungs by coughing a specimen of mucus (not saliva or spit from the mouth) from deep inside your lungs into a container. If coughing does not produce sputum, a breathing treatment may precede the test to induce or encourage sputum production.

If you have a dry cough or are unable to produce a specimen, bronchoscopy may be necessary.

How the test will feel Return to top

The person needing the test will usually have a productive cough. Occasionally, the sputum is collected by bronchoscopy, and more discomfort is associated with this procedure.

Why the test is performed Return to top

The test is performed when there is a persistent or prolonged cough, sputum has a foul odor or unusual color, respiratory disease is suspected, or there is a generalized infection.

Normal Values Return to top

No presence of organisms is normal. The sputum is clear, thin, and odorless.

What abnormal results mean Return to top

A bacterial infection may be present. The infecting organisms may be tentatively identified. Culture is needed to confirm the diagnosis.

What the risks are Return to top

There are no risks unless a bronchoscopy is used to obtain the specimen.

Special considerations Return to top

The test may need to be repeated if the specimen produced contains only saliva from the mouth.

Update Date: 1/26/2004

Updated by: Daniel Levy, M.D., Ph.D., Infectious Diseases, Greater Baltimore Medical Center, Baltimore, MD. Review provided by VeriMed Healthcare Network.

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