Cryptococcus — India Ink Encapsulated Yeast

A 38-year-old man with advanced HIV (CD4 count 45/μL) presents to a tertiary care center in Delhi with a 3-week history of progressive headache, fever, and altered mental status. Lumbar puncture is performed, and CSF is examined under light microscopy after preparation with the technique shown at **D** in the diagram. The examiner observes round yeast cells surrounded by a clear halo against a black background. Which of the following best explains why this negative staining technique is particularly useful for identifying this organism in CSF?