Track: Basic Science

Topic: Infectious Diseases

Abstract:

It is well known that both PAS and GMS staining is effective in highlighting fungal organisms in tissues. PAS appears occasionally less effective than GMS, although multiple studies show no significant difference between the two. Some authors have claimed that the superiority of GMS stems from its ability to stain degenerate and nonviable fungal organisms, while PAS weakly or not at all. To address this issue, the following experiments were carried out. Degenerate Trichophyton rubrum and Aspergillus (A. brasiliensis; A. fumigatus; A. flavus) colonies were prepared by exposing them to fluconazole (0.068, 0.4, 2.0 mg/mL) and amphotericin B (5 mg/mL), as well as formic acid (6%), hydrochloric acid (2.75%), bleach (sodium hypochlorite, 3%), and nail softener (potassium hydroxide, 17%) for 20, 48, and 65 hours on culture media. The fungal organisms were then examined and stained with PAS and GMS. Gross examination of fungal plates showed depressed growth and discoloration at the areas of treatment. Microscopic examination revealed fungal degeneration in treated groups, indicated by decreased number, variations in shape and size, swollen hyphae, and intracellular vesicles. A spectrum of no change to a decrease in staining intensity of the degenerate fungi on PAS or GMS was observed, with similar findings seen across the different treatment groups. No significant difference between PAS and GMS staining on the degenerated fungi was observed. In conclusion, degeneration of Trichophyton and Aspergillus produced minimal change to a decrease in staining intensity on PAS and GMS, with no significant difference between PAS and GMS staining.

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Gordon Love, M.D.