Gram stain of urethral discharge

Urethral discharge Gram stain; Urethritis - Gram stain

A Gram stain of urethral discharge is a test used to identify bacteria in fluid from the tube that drains urine from the bladder (urethra).

How the Test is Performed

Fluid from the urethra 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.

The stained smear is then examined under the microscope for the presence of bacteria. The color, size, and shape of the cells help identify the type of bacteria causing the infection.

How to Prepare for the Test

This test is often performed in the health care provider's office.

How the Test will Feel

You may feel pressure or burning when the cotton swab touches the urethra.

Why the Test is Performed

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

Normal Results

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate gonorrhea or other infections.

Risks

There are no risks.

Considerations

A culture of the specimen (urethral discharge culture) should be performed in addition to the Gram stain. More advanced tests (such as PCR tests) may also be done.

Open References

References

Babu TM, Urban MA, Augenbraun MH. Urethritis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 107.

Swygard H, Cohen MS. Approach to the patient with a sexually transmitted infection. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 269.

Gram stain of urethral discharge - illustration
The gram stain procedure is a method of staining microorganisms on a slide using crystal violet to be viewed later under a microscope.
Gram stain of urethral discharge
illustration
Gram stain - illustration
A Gram stain is a test used to help identify bacteria. The tested sample can be taken from body fluids that do not normally contain bacteria, such as blood, urine, or cerebrospinal fluid. A sample can also be taken from the site of a suspected infection, such as the throat, lungs, genitals, or skin. Bacteria are classified as either Gram-positive or Gram-negative, based on how they color in reaction with the Gram stain. The Gram stain is colored purple. When combined with the bacteria in a sample, the stain will either stay purple inside the bacteria (Gram-positive), or it will turn pink (Gram-negative). Examples of Gram-positive bacteria include Streptococcus and Staphylococcus aureus, as well as bacteria that cause anthrax, diphtheria, and toxic shock syndrome. Examples of Gram-negative bacteria include Escherichia coli (E coli), Salmonella, Hemophilus influenzae, as well as many bacteria that cause urinary tract infections, pneumonia, or peritonitis. Gram stain can be done within a few hours. The results help providers choose the first antibiotics to use. Cultures of bacteria help identify specific bacteria, but take days to complete.
Gram stain
illustration

A Closer Look

Urinary tract infection - InDepth

Self Care

Tests for Gram stain of urethral discharge

Review Date: 10/20/2022

Health Content Provider

06/01/2025

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