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Ency. home > Test > J > Joint fluid Gram stain

Joint fluid Gram stain   

Overview | Risks | Results

Alternative names:

Gram stain of joint fluid

Definition:

A method of staining microorganisms (bacteria) using a special series of stains. In this test, a specimen of joint 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

The skin around the joint is cleaned, a needle is inserted into the joint, and fluid is aspirated. 

A drop of the joint fluid is then applied in a very thin layer to a microscope slide -- this is called a smear. The specimen is stained with a series of stains, together called a Gram stain. 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 make it possible to identify the infecting organism.

How to Prepare for the Test

Adult:
There is no special preparation for the test. It may be performed in the health care provider's office.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

How the Test will Feel

The joint is cleansed with an anti-bacterial soap. An anesthetic may be injected into the joint, and a stinging sensation may be felt. A needle is then inserted into the joint, and a small amount of fluid is withdrawn into a syringe. Pressure and pain in the joint may be present.

Why the Test is Performed

The test is performed for unexplained swelling, joint pain, and inflammation of a joint or suspected joint infection.

Ency. home > Test > J > Joint fluid Gram stain

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