Detection of Fungal Organisms in Eosinophilic Mucin Using a Fluorescein-labeled Chitin-specific Binding Protein

Background: The ability to identify fungal hyphae in patients with chronic rhinosinusitis (CRS) has been inconsistent. A new fluorescein-labeled staining method targets chitin found in fungal cell walls.

Objective: We hypothesize that this method would be able to more consistently detect fungi within the mucin of CRS patients.

Methods: Fifty-four consecutive CRS surgical patients were evaluated. After ensuring sensitivity and specificity of this new method, all specimens were stained with either fluorescein-labeled chitinase or Grocott methanamine silver stain for comparison.

Results: All 54 specimens contained eosinophilic mucin on hematoxylin and eosin staining. One or more fungal hyphae could be visualized within the mucin of 54 (100%) of 54 specimens stained using the fluorescein-labeled chitinase. Only 41 (76%) of 54 of the specimens stained with the Grocott methanamine silver stain technique demonstrated fungi.

Conclusion: The fluorescein-labeled chitinase-staining technique has greater sensitivity in detecting fungal organisms within eosinophilic mucin. Fungal organisms are present in the mucin of CRS patients.