Gram stain of urethral discharge

Alternative names
Urethral discharge Gram stain


A Gram stain is a method of staining microorganisms (bacteria) using a special series of stains. In a Gram stain of urethral discharge, a smear of fluid from the urethra is stained and then examined under the microscope.

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

A urethral discharge is collected on a cotton swab. A sample from this swab is applied in a very thin layer to a microscope slide. 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
This test is often performed in the health care provider’s office.

Infants and children:
The preparation you can provide for this test depends on your child’s age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:

  • Infant test or procedure preparation (birth to 1 year)  
  • Toddler test or procedure preparation (1 to 3 years)  
  • Preschooler test or procedure preparation (3 to 6 years)  
  • Schoolage test or procedure preparation (6 to 12 years)  
  • Adolescent test or procedure preparation (12 to 18 years)

How the test will feel
The sensation of pressure or burning may be present when the cotton swab is in contact with the urethra.

Why the test is performed
The test is performed when an abnormal urethral discharge is present. It may be performed if infection with a sexually transmitted disease is suspected.

Normal Values
No presence of organisms is normal.

What abnormal results mean
Abnormal results may indicate infection with gonorrhea or other infections (see Gonorrhea-Male).

What the risks are
There are no risks.

Special considerations
A culture of the specimen (urethral discharge culture) should be performed in addition to the Gram stain. More sophisticated diagnostic tests (such as PCR tests) are sometimes also done.

Johns Hopkins patient information

Last revised: December 8, 2012
by Brenda A. Kuper, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.