MedlinePlus

Gram Stain: MedlinePlus Medical Test

What do the results mean?

Your sample will be placed on a slide and treated with the Gram stain. A laboratory professional will examine the slide under a microscope. If no bacteria were found, it means you probably don’t have a bacterial infection or there weren’t enough bacteria in the sample.

If bacteria were found, it will have certain qualities may provide important information about your infection:

  • If the bacteria was colored purple, it means you likely have a Gram-positive infection.
  • If the bacteria was colored pink or red, it means you likely have a Gram-negative infection.

Your results will also include information about the shape of the bacteria in your sample. Most bacteria are either round (known as cocci) or rod-shaped (known as bacilli). The shape can provide more information about the type of infection you have.

Although your results may not identify the exact type of bacteria in

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