WHAT IS GRAM STAIN TEST?
Gram staining divides bacteria into two groups according to their staining properties: gram–negative and gram–positive. The staining involves placing drops of crystal violet dye onto the specimen sample, washing off the violet stain, and flooding the smear with an iodine solution followed by a 95% ethyl alcohol (ethanol) solution. Gram-positive cells remain blue, and gram-negative cells are decolourised by the alcohol. The specimen is then stained with a red dye called “safranin O,” which colours the gram-positive cells red and leaves the gram-negative cells appearing purple. The cell wall structure is the basis of the Gram reaction. Gram staining of specimens aids in decision-making for early, broad-spectrum antibiotic therapy. Gram stain is 67.9% sensitive for the detection of bacteria in blood cultures.