Questions and Answers
Which diagnostic method utilizes ultraviolet rays to aid clinical diagnosis?
What is a primary source of endogenous Candida infection?
Which of the following is NOT a clinical manifestation of Candida infections?
What is the result of prolonged use of certain medications in relation to Candida infections?
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Which of the following infections can be caused by Candida?
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Which of the following components is found in the fungal cell wall?
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What type of metabolism do most fungi predominantly exhibit?
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What is the optimal temperature range for fungal growth?
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How do yeasts typically reproduce?
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Which type of fungi exists in both yeast and mold forms depending on environmental conditions?
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What type of hyphae grow above the surface of media and carry spores?
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In sexual reproduction of fungi, what is involved?
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What type of environment do fungi generally prefer for growth?
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What is the main method of reproduction for fungi?
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Which of the following mycoses is caused by the organism Candida?
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What type of fungus is commonly associated with superficial mycosis?
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Which method is NOT typically used for the diagnosis of fungal infections?
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Which type of sample is NOT typically used for the diagnosis of fungal infections?
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What is the function of adding chloramphenicol and cyclohexamide to Sabouraud's dextrose agar?
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What type of mycosis occurs in immunocompromised hosts?
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Which stain is used for a stained preparation in the diagnosis of fungal infections?
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Study Notes
Fungal Cell Structure
- Fungal cell walls contain glucan and chitin.
- Cell membranes are characterized by the presence of sterols.
- Fungi are classified into yeast, mold, yeast-like, and dimorphic forms.
- Fungi reproduce via sexual and asexual means.
Fungal Metabolism
- Aerobic metabolism is present in all fungi; some can also survive as facultative anaerobes.
- Optimal growth temperature ranges from 25 to 30 ºC, aligning with their saprophytic lifestyle.
- Fungi can thrive in a wide range of pH (2–9), generally favoring acidic environments.
Classification of Fungi
- Yeasts are unicellular and reproduce by budding, resulting in pseudohyphae.
- Examples include Cryptococcus neoformans for yeasts and Candidiasis for candida.
- Moulds are filamentous fungi, with hyphae being either septated or non-septated.
- Dimorphic fungi exhibit two morphological forms: yeast and hyphae, like Histoplasma capsulatum.
Fungal Reproduction
- Sexual reproduction involves the fusion of two nuclei or gametes.
- Asexual reproduction is predominant and occurs via fragmentation of hyphae or budding, leading to individual fungi.
Mycosis Naming
- Mycosis is named after the causative organism, e.g., Candidiasis, Aspergillosis, Cryptococcosis, and Histoplasmosis.
- Mycosis can also be categorized based on the site of infection, such as pulmonary mycosis.
Types of Human Mycosis
- Categories include superficial, cutaneous, subcutaneous, systemic, and opportunistic infections.
- Opportunistic infections primarily affect immunocompromised individuals, usually entering through inhalation of spores or direct implantation.
Diagnosis of Fungal Infections
- Samples are collected based on infection sites such as skin, hair, and nails.
- Direct microscopic preparation uses KOH (10-30%) for unstained samples and lactophenol cotton blue for stained preparations.
- Fungi can be isolated through culture on media such as Sabouraud's dextrose agar (SDA) or SDA supplemented with chloramphenicol and cyclohexamide to inhibit contaminants.
Diagnosis Techniques
- Woods light examination detects fungal infections via fluorescent reactions to ultraviolet rays.
- Serological diagnosis, including ELISA, is utilized for candidal infections.
Source and Predisposing Factors of Infection
- Endogenous sources arise from normal flora present in the oral cavity, gastrointestinal tract, and skin.
- Exogenous sources can occur through sexual contact.
- Predisposing factors include age extremes, immunosuppression (due to pregnancy, diabetes, or immunosuppressive drugs), and traumatic conditions like catheterization.
Clinical Manifestations of Candidiasis
- Mucocutaneous infections may include oral thrush and vaginitis.
- Cutaneous infections manifest in areas like the napkin region in babies and can include nail infections.
- Systemic infections can affect urinary tracts, lead to endocarditis, CNS infections like meningitis, and systemic placements like septicemia and fungemia.
Laboratory Diagnosis of Candidiasis
- Microscopic examination is done using KOH for unstained samples or lactophenol cotton blue for stained samples to detect yeast cells and pseudohyphae.
- Culturing on SDA helps isolate candida.
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Description
This quiz explores the fundamental concepts of Medical Mycology, including the structures and classifications of fungi. Topics covered include eukaryotic fungal cell walls, yeast, molds, and dimorphic fungi. Ideal for students of medical microbiology.
