What is a Gram stain?
A Gram stain is a test that checks for bacteria at the site of a suspected infection or in certain body fluids, such as blood or urine. These sites include the throat, lungs, and genitals, and in skin wounds.
There are two main categories of bacterial infections: Gram-positive and Gram-negative. The categories are diagnosed based on the how the bacteria reacts to the Gram stain. A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative. The two categories cause different types of infections:
Gram-positive infections include methicillin-resistant Staphylococcus aureus (MRSA), strep infections, and toxic shock.
Gram-negative infections include salmonella, pneumonia, urinary tract infections, and gonorrhea.
A Gram stain may also be used to diagnose fungal infections.
Other names: Gram's stain
