Gram stain of tissue biopsy

• How the test is performed

  A sample, called a smear, from a tissue specimen is usually applied in a very thin layer to a microscope slide. The specimen is stained with crystal violet stain and undergoes additional processing before it is examined under the microscope for the presence of microorganisms. Different characteristics of the microoganisms, such as color, shape and pattern of staining, help determine the type of microorganism.

• How to prepare for the test

  If the biopsy is included as part of a surgical procedure, you will be asked not to eat or drink anything the night before surgery. If the biopsy is of a superficial (on the surface of the body) tissue, you may be asked not to eat or drink for several hours before the procedure.

• How the test will feel

  How the test feels depends on the part of the body being biopsied. There are several different methods for obtaining tissue samples. A needle may be inserted through the skin to the specific tissue. An cut (incision) through the skin into the tissue may be made, with a small piece of the specific tissue removed.

  A biopsy may also be taken from inside the body by an instrument that helps the doctor see inside the body, such as an endoscope or cystoscope. Some form of anesthetic is usually given so there is little or no pain. Pressure and occasional mild pain may be felt during a biopsy.

• Why the test is performed

  The test is performed when an infection of a body tissue is suspected.

• Normal Values

  The presence or type of organisms depends on the particular tissue being biopsied. Some tissues in the body are sterile, such as the brain, whereas other tissues normally contain organisms.

  Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

• What abnormal results mean

  Abnormal results usually indicate an infection in the tissue site. Further tests, such as culturing the biopsied material, are frequently needed to identify the specific type of organism involved.

• What the risks are

  The only risks are those associated with obtaining a tissue biopsy and may include bleeding or infection.

Review Date: 5/30/2009

Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.