A pseudo-cryptococcal artefact derived from leucocytes in wet India ink mounts of centrifuged cerebrospinal fluid

Abstract

Wet India ink mounts of cerebrospinal fluid (CSF) are useful in the laboratory diagnosis of cryptococcal meningitis. Pseudo-cryptococcal artefacts in such mounts have been attributed to leucocytes in CSF but their mode of formation has not been explained. This report describes the reproduction of such an artefact in cryptococcus free CSF-leucocyte mixtures that had been subjected to high speed centrifugation. The viscosity of DNA that could provide a morphological pseudo-capsule, and the yellow-green fluorescence of the pseudo-capsular material on staining with acridine- orange, suggest that lymphocytic nuclear DNA, which possibly leaked out after damage to the lymphocyte membrane by centrifugation, was responsible for this artefact.