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A pseudo-cryptococcal artefact derived from leucocytes in wet India ink mounts of centrifuged cerebrospinal fluid
N Thiruchelvan1, K Y Wuu, S N Arseculeratne
1Department of Microbiology and Parasitology, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.
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.
Insights
Pseudo-cryptococcal artefacts in cerebrospinal fluid (CSF) diagnostic tests can be formed by lymphocyte nuclear DNA. This DNA may leak out and create a false capsule after high-speed centrifugation of CSF samples.
Area of Science:
- Medical Laboratory Science
- Clinical Diagnostics
- Microbiology
Background:
- Wet India ink mounts are crucial for diagnosing cryptococcal meningitis using cerebrospinal fluid (CSF).
- Pseudo-cryptococcal artefacts, often mistaken for fungi, have been observed in these mounts.
- The origin of these artefacts, previously attributed to leukocytes, remained unclear.
Purpose of the Study:
- To investigate the formation mechanism of pseudo-cryptococcal artefacts in CSF.
- To determine the role of leukocytes and their components in artefact generation.
Main Methods:
- CSF samples, free of cryptococcus but containing leukocytes, were subjected to high-speed centrifugation.
- The resulting mixtures were analyzed using wet India ink mounts.
- Staining with acridine-orange was performed to assess the nature of the artefact material.
Main Results:
- An artefact resembling cryptococcus was successfully reproduced in CSF-leukocyte mixtures post-centrifugation.
- The artefact material exhibited yellow-green fluorescence with acridine-orange staining.
- This fluorescence is characteristic of DNA, suggesting a nuclear origin.
Conclusions:
- Lymphocytic nuclear DNA, released after membrane damage during centrifugation, is likely responsible for pseudo-cryptococcal artefacts.
- This finding clarifies a potential diagnostic pitfall in cryptococcal meningitis testing.
- Understanding artefact formation improves the accuracy of CSF analysis.