Paint It Black: Staining of the Yeast Cryptococcus Neoformans with India Ink

Aims: To rectify the application of negative staining using India Ink dye in order to visualize the opportunistic yeast, Cryptococcus neoformans and its capsule.

Discussion: The yeast C. neoformans is generally considered an opportunistic fungal pathogen due to its propensity to infect immunocompromised hosts, particularly those with HIV (+). This yeast responsible for causing severe disseminated Cryptococcus meningoencephalitis (CM) in humans. The type of clinical sample commonly sent for laboratory analysis of suspected patients is the cerebrospinal fluid (CSF) that usually obtained from spinal tap or lumbar puncture procedure. laboratory analysis to confirm CM initially by direct visualization of Cryptococci via light microscopy. Visualization of capsule, as the hallmark of C. neoformans is easy when appropriate number of yeasts are available in the clinical sample. India Ink is the dye of choice to stain C. neoformans and its capsule. The pathognomonic resemblance of its capsule is that of a halo appearance, whether thin or thick, surrounding the cell made visible by suspending the yeast in India ink preparations.

Conclusion: India ink stain is still widely used for the detection of cryptococci in CSF, particularly in resource-limited laboratory/health service. Its sensitivity can be improved.