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Advantage of Fontana-Masson stain in capsule-deficient cryptococcal infection
Abstract:
We describe light and electron microscopic findings in three cases of pulmonary infection caused by capsule-deficient Cryptococcus neoformans (CDCN) and emphasize the value of the Fontana-Masson silver (FMS) stain in diagnosing cryptococcosis. Capsule-deficient C neoformans infections, including coccidioidomycosis, histoplasmosis, typical cryptococcosis, blastomycosis, candidiasis, and pneumocystosis were used as controls. Several stains including mucicarmine, alcian blue, and FMS were done on tissue sections from all of the above mentioned infections. It was found that while the FMS stain was positive only in the organisms of CDCN and typical C neoformans, the mucicarmine was positive only in typical C neoformans. The negativity of the mucicarmine in the organisms of CDCN reflected the absence of capsular material as demonstrated by ultrastructural study. Therefore, when fungal cultures are not available or are negative, and tissue mucicarmine is negative, the FMS stain is a valuable alternative for use on tissue sections. It may be used, along with routine fungal stains, when a yeast-forming fungal infection is suspected.
Insights
The Fontana-Masson silver stain aids in diagnosing pulmonary cryptococcosis, especially for capsule-deficient Cryptococcus neoformans (CDCN) infections. This stain is valuable when other methods like mucicarmine stain are negative.
Area of Science:
- Medical Mycology
- Pathology
- Microbiology
Background:
- Pulmonary infections caused by fungi are a significant clinical concern.
- Cryptococcus neoformans (C. neoformans) is an opportunistic fungal pathogen.
- Capsule-deficient C. neoformans (CDCN) presents diagnostic challenges.
Purpose of the Study:
- To evaluate the diagnostic utility of the Fontana-Masson silver (FMS) stain for pulmonary infections.
- To compare FMS stain with other histological stains in identifying fungal elements.
- To highlight FMS stain's effectiveness in diagnosing CDCN infections.
Main Methods:
- Light and electron microscopy were employed to examine pulmonary tissue samples.
- Histological stains including mucicarmine, alcian blue, and FMS were applied.
- Tissue sections from CDCN and other fungal infections (controls) were analyzed.
Main Results:
- The FMS stain demonstrated positivity in both CDCN and typical C. neoformans.
- Mucicarmine stain was positive only in typical C. neoformans, reflecting the absence of capsule in CDCN.
- Electron microscopy confirmed the absence of capsular material in CDCN.
Conclusions:
- The FMS stain is a valuable diagnostic tool for cryptococcosis, particularly for CDCN.
- When fungal cultures are unavailable or negative and mucicarmine stain is uninformative, FMS stain offers an alternative.
- FMS stain should be considered alongside routine fungal stains for suspected yeast-forming fungal infections.