A Gram stain is a type of test that helps tell whether bacteria causing an infection are Gram-positive or Gram-negative. This can help a doctor choose the right antibiotic to treat the infection.
The Gram stain is done by putting a special dye on the bacterial cells. Gram-positive bacteria retain the dye and turn a different color than Gram-negative bacteria do. Sometimes more testing is done after the Gram stain to identify the specific kind of bacteria and the antibiotics that can kill them.
How this information was developed to help you make better health decisions.