Endocervical Gram stain

Alternative names 
Gram stain of cervix


Gram stain is a method of staining microorganisms (bacteria) using a special series of stains. In this test, a specimen from the cervix 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 tissue sample is obtained from the lining of the cervical canal (the opening to the uterus). You lie on your back with your feet in stirrups (devices that support your feet and help keep you in proper position).

As in a regular pelvic examination, a speculum (an instrument used to stretch open the vagina in order to better examine some of the pelvic organs) will be inserted and opened slightly.

The cervix is cleaned so there is no mucus. A dry, sterile swab is then inserted and rotated within the cervical canal. It may be left in place for several seconds to absorb as many of the organisms as possible.

The swab is then removed and sent to a laboratory where it will be smeared on a 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
Do not douche for 24 hours before the procedure.

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 adolescent test or procedure preparation (12 to 18 years).

How the test will feel
There may be minor discomfort during specimen collection. This procedure feels very much like a routine Pap smear.

Why the test is performed
The test is used to detect and identify abnormal bacteria in the area involving the cervix. If signs of an infection develop or a sexually transmitted disease (such as gonorrhea) is suspected, this test can help with confirmation and identification of an abnormal organism.

Normal Values
There are no abnormal bacteria present. Note that the normal cervix has “friendly” bacteria that should be seen by Gram stain.

What abnormal results mean

  • Gonorrhea  
  • Chlamydia  
  • Bacterial vaginosis  
  • Yeast infection

Additional conditions under which the test may be performed include gonococcal arthritis, in order to determine the site of the initial infection.

What the risks are
There is virtually no risk.

Special considerations
If gonorrhea or another sexually transmitted infection is present, it is very important that all sexual partners of the infected person receive treatment also, even if there are no symptoms.

Johns Hopkins patient information

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

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