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Questions and Answers
What is the main stain used in stained preparations of fungi?
What is the main stain used in stained preparations of fungi?
- Methylene blue
- Crystal violet
- Eosin
- Lactophenol cotton blue (correct)
Which temperature is primarily required for the growth of yeast fungi?
Which temperature is primarily required for the growth of yeast fungi?
- 30-35°C
- 25-27°C
- 37°C (correct)
- 20-25°C
What is one diagnostic use of detecting β-D-Glucan in blood samples?
What is one diagnostic use of detecting β-D-Glucan in blood samples?
- Detect invasive fungal infections (correct)
- Diagnose bacterial infections
- Diagnose systemic mycosis
- Identify superficial fungal infections
Which method is NOT a part of laboratory diagnostic tests for fungal infections?
Which method is NOT a part of laboratory diagnostic tests for fungal infections?
Which agent inhibits ergosterol synthesis in fungal cell membranes?
Which agent inhibits ergosterol synthesis in fungal cell membranes?
What is the typical incubation period to obtain positive cultures for fungi?
What is the typical incubation period to obtain positive cultures for fungi?
Which of the following fungi is known to be detected using the Galactomannan test?
Which of the following fungi is known to be detected using the Galactomannan test?
What type of sample is required for a wet mount preparation in fungal diagnosis?
What type of sample is required for a wet mount preparation in fungal diagnosis?
Flashcards
KOH preparation
KOH preparation
A type of microscopic examination that uses a wet mount and a drop of potassium hydroxide (KOH) solution to dissolve skin cells and highlight fungal elements.
Lactophenol cotton blue staining
Lactophenol cotton blue staining
A direct microscopic examination method that uses a stain called Lactophenol cotton blue to visualize fungal structures.
Sabouraud's dextrose agar (SDA)
Sabouraud's dextrose agar (SDA)
A type of fungal culture medium that is enriched and selective for the growth of fungi.
Fungal Culture
Fungal Culture
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Azoles
Azoles
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Polyenes
Polyenes
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Caspofungin
Caspofungin
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Flucytosine
Flucytosine
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Study Notes
Introduction to Medical Mycology (I & II)
- Lecture focused on medical mycology, covering general properties, structure, morphology, classification, and human mycosis.
- Includes a section on laboratory diagnosis of fungal infections.
Content of Lecture
- General properties and structure of fungi
- Morphology of fungi
- Classification of medically important fungi
- Human mycosis
Laboratory Diagnosis of Fungal Infections
- Specimens: Skin scrapings, hairs, nails, respiratory secretions, and blood are used according to the infection site.
- Laboratory Diagnostic Tests:
- Direct microscopic examination
- Fungal culture
- Serological tests
- Skin tests
- Molecular methods (e.g., PCR)
1-Direct Microscopic Examination
- Unstained preparations (wet mount): A drop of 10-30% potassium hydroxide (KOH) is added to skin scrapings, nails, or hairs for examination.
- Stained preparations: Lactophenol cotton blue (main stain); Silver stain; Periodic acid-Schiff (PAS) stain are used for visualization.
2. Fungal Culture
- All fungi are aerobic.
- Temperature requirements: Most fungi grow at 25-27°C; yeasts grow at 37°C; dimorphic fungi grow at both 25°C and 37°C.
- Incubation time: Positive fungal cultures are typically obtained within 7-10 days; Candida and Aspergillus require 24-72 hours or 4 weeks depending on the fungus.
- Sabouraud's dextrose agar (SDA): Used as enriched and selective media to grow fungi. Examples of fungal growth on SDA are Aspergillus niger and Aspergillus flavus.
3. Serological Tests
- Antigen and antibody detection:
- Detection of β-D-glucan in blood samples can diagnose invasive fungal infections.
- Galactomannan detection in blood samples is used to diagnose invasive aspergillosis.
- Detecting antibodies is used to diagnose systemic mycosis.
Antifungal Therapy
- Mechanism of action:
- Caspofungin: Inhibits cell wall synthesis.
- Polyenes (e.g., nystatin, amphotericin B): Inhibit ergosterol synthesis in the cell membrane.
- Azoles (e.g., miconazole, fluconazole): Inhibit ergosterol synthesis.
- Flucytosine: Inhibits DNA synthesis.
Key Questions and Answers
- Component of fungi cell membrane: Ergosterol
- Tinea pedis: Fungal infection of the toe web.
- Antifungal agent inhibiting nucleic acid synthesis: Flucytosine.
- Yeast fungi example: Candida albicans
References
- Lippincott Illustrated Microbiology 4th edition, Chapters 20
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