Direct Microscopic Examination of Fungi PDF
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This document outlines various methods for identifying fungi using microscopy. It describes temporary and permanent mounts, including KOH preparation, calcofluor white, and stains like PAS and Gram stain. Different stains highlight specific fungal characteristics or structures.
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DIRECT MICROSCOPIC EXAMINATION Provides rapid report Specific morphologic characteristics provide a clue to genus of organism. Might provide evidence of infection despite negative cultures DIRECT MICROSCOPIC EXAMINATION A.Temporary mounts KOH KOH with calcoflour white Lactophenol blue Indi...
DIRECT MICROSCOPIC EXAMINATION Provides rapid report Specific morphologic characteristics provide a clue to genus of organism. Might provide evidence of infection despite negative cultures DIRECT MICROSCOPIC EXAMINATION A.Temporary mounts KOH KOH with calcoflour white Lactophenol blue India ink B. Pemanent mounts KOH PREPATION 10-20% KOH solution embedded with skin, nails and tissue. KOH breaks down keratin and skin layer to see more easily any fungi present in the specimen. Gentle heat increase rate of clearing Modified KOH: using DMSO – dimethyl sulfoxide To facilitate more rapid breakdown of cellular debris w/o requiring heating. KOH WITH CALCOFLOUR A drop of calcofluor white (fluorescent dye) can be added. Dye binds to polysaccharides in the chitin Fungal element =apple green or blue white depends on the filter of the microscope INDIA INK/ NIGROSIN Used to examine CSF for the presence of encapsulated yeast Crytococcus neoformans Fungal element = yeast with clear halo Background = black B. PERMANENT MOUNTS. PAS (Periodic acid Schiff) a. differentiation of fungi scrapings of tissue b. carbohydrates in fungus wall stain purplish red c. H&E slides may be restained by this when fungus wall invisible Fungal element =Magenta Background color= Pink or green B. PERMANENT MOUNTS 2. Gram stain a. all fungi are Gram positive b. stain employs crystal violet and ammonium oxalate B. PERMANENT MOUNTS 3. Acid-fast stain a. useful for differentiation of Nocardia from Actinomyces b. hyphae of Nocardia partially acid fast or acid fast (red) B. PERMANENT MOUNTS 4. Gomori methenamine-silver nitrate a. fungal element- black background = green 5. Giemsa a. used primarily to detect Histoplasma capsulatum in bone marrow or blood fungal element= purple blue yeast with clear halo (capsule) background = pink-purple B. PERMANENT MOUNTS 6. Acridine orange a. fungal element- green fluorescent epithelial cells = orange
