Questions and Answers
What is the characteristic appearance of fungi when viewed with KOH and calcofluor white under a microscope?
Which microscopy technique is specifically used to examine CSF for the presence of encapsulated yeast?
What dye is used in Gomori methenamine-silver nitrate stains?
What is the characteristic color of fungal elements observed with PAS staining?
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In the context of direct microscopic examination, what is the purpose of using 10-20% KOH solution?
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How does the appearance of fungi differ in an acid-fast stain when comparing Nocardia to Actinomyces?
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What characteristic indicates a fungal element when viewed with Giemsa stain?
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What color do fungal elements appear when viewed using acridine orange stain?
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Which of the following methods can be used for the direct microscopic examination of fungi?
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What special characteristic does KOH preparation provide for examining fungi?
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KOH preparation can be used to see more easily any fungi present in a specimen.
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What color does the fungal element appear when using calcofluor white in KOH preparation?
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What is the background color when using India ink to examine CSF for Cryptococcus neoformans?
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Which stain is used primarily to detect Histoplasma capsulatum?
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What color do fungal elements appear when stained with Gomori methenamine-silver nitrate?
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All fungi are Gram positive according to Gram stain results.
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What is the result of using acid-fast stain on Nocardia?
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Study Notes
Direct Microscopic Examination
- Provides a rapid report on potential infections.
- Specific morphologic characteristics can indicate the genus of the organism.
- May reveal evidence of infection even when cultures return negative results.
Temporary Mounts
-
KOH Preparation:
- 10-20% KOH solution used on skin, nails, and tissues.
- KOH dissolves keratin, facilitating the visualization of fungi.
- Gentle heating increases clearing rates.
-
Modified KOH:
- Utilizes DMSO to accelerate breakdown of cellular debris without heat.
-
KOH with Calcofluor White:
- A fluorescent dye that binds to chitin polysaccharides in fungal cell walls.
- Fungal elements will appear apple green or blue-white, depending on the microscope filter.
-
India Ink/Nigrosin:
- Effective for examining CSF for encapsulated yeast, particularly Cryptococcus neoformans.
- Fungal elements show as yeasts with a clear halo against a black background.
Permanent Mounts
-
PAS (Periodic Acid Schiff):
- Highlights carbohydrates in the fungal cell wall, staining them purplish-red.
- Useful for differentiating fungal scrapings from tissues.
- When fungal walls are invisible on H&E slides, they may be restained with PAS.
- Fungal elements appear magenta; background can be pink or green.
-
Gram Stain:
- All fungi are Gram positive, utilizing crystal violet and ammonium oxalate for staining.
-
Acid-Fast Stain:
- Differentiates Nocardia from Actinomyces.
- Hyphae of Nocardia can be partially or fully acid-fast, appearing red.
-
Gomori Methenamine-Silver Nitrate:
- Fungal elements are stained black, creating a green background.
-
Giemsa Stain:
- Mainly used to identify Histoplasma capsulatum in bone marrow or blood.
- Fungal elements appear as purple-blue yeasts with a clear halo (capsule) against a pink-purple background.
-
Acridine Orange:
- Fungal elements appear green fluorescent; epithelial cells stain orange.
Direct Microscopic Examination
- Provides a rapid report on potential infections.
- Specific morphologic characteristics can indicate the genus of the organism.
- May reveal evidence of infection even when cultures return negative results.
Temporary Mounts
-
KOH Preparation:
- 10-20% KOH solution used on skin, nails, and tissues.
- KOH dissolves keratin, facilitating the visualization of fungi.
- Gentle heating increases clearing rates.
-
Modified KOH:
- Utilizes DMSO to accelerate breakdown of cellular debris without heat.
-
KOH with Calcofluor White:
- A fluorescent dye that binds to chitin polysaccharides in fungal cell walls.
- Fungal elements will appear apple green or blue-white, depending on the microscope filter.
-
India Ink/Nigrosin:
- Effective for examining CSF for encapsulated yeast, particularly Cryptococcus neoformans.
- Fungal elements show as yeasts with a clear halo against a black background.
Permanent Mounts
-
PAS (Periodic Acid Schiff):
- Highlights carbohydrates in the fungal cell wall, staining them purplish-red.
- Useful for differentiating fungal scrapings from tissues.
- When fungal walls are invisible on H&E slides, they may be restained with PAS.
- Fungal elements appear magenta; background can be pink or green.
-
Gram Stain:
- All fungi are Gram positive, utilizing crystal violet and ammonium oxalate for staining.
-
Acid-Fast Stain:
- Differentiates Nocardia from Actinomyces.
- Hyphae of Nocardia can be partially or fully acid-fast, appearing red.
-
Gomori Methenamine-Silver Nitrate:
- Fungal elements are stained black, creating a green background.
-
Giemsa Stain:
- Mainly used to identify Histoplasma capsulatum in bone marrow or blood.
- Fungal elements appear as purple-blue yeasts with a clear halo (capsule) against a pink-purple background.
-
Acridine Orange:
- Fungal elements appear green fluorescent; epithelial cells stain orange.
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Description
This quiz covers direct microscopic examination methods used in microbiology, focusing on KOH preparations and their role in identifying fungi and infections. It also discusses temporary and permanent mounts essential for visualizing various pathogens. Test your understanding of these techniques and their applications in clinical settings.
