Negative Stain (India Ink)

Also known as India Ink, the negative stain is employed to detect the presence of microorganisms, especially pathogenic yeast, in body fluids. The principle behind this test is that the negative India ink staining creates a black, semi-opaque background, making the yeast capsules clearly visible under the microscope.

This test is used to detect the presence of cryptococcal organism C. neoformans in a person’s cerebrospinal fluid (CSF). Since C. neoformans are composed of encapsulated yeast cells, the capsules bind easily with the India ink stain to become visible. This organism is present in the environment and can cause cryptococcal infections, a deadly fungal infection in humans.