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Questions and Answers
A patient presents with a lung infection and a subsequent dissemination to the skin and bones. Microscopic examination reveals broad-based budding yeast. Which of the following fungal pathogens is the MOST likely cause of this infection?
A patient presents with a lung infection and a subsequent dissemination to the skin and bones. Microscopic examination reveals broad-based budding yeast. Which of the following fungal pathogens is the MOST likely cause of this infection?
- Blastomyces dermatitidis (correct)
- Paracoccidioides brasiliensis
- Histoplasma capsulatum
- Coccidioides immitis
A patient is diagnosed with Valley fever. Which characteristic transformation occurs in the lungs with the causative fungal pathogen?
A patient is diagnosed with Valley fever. Which characteristic transformation occurs in the lungs with the causative fungal pathogen?
- Formation of spherules filled with endospores (correct)
- Multiple budding yeast with a pilot wheel appearance
- Intracellular yeast formation inside macrophages
- Development of non-septate hyphae with right-angle branching
An immunocompromised patient develops thrush, esophagitis, and vaginitis. Which of the following fungal pathogens is MOST likely responsible for these conditions?
An immunocompromised patient develops thrush, esophagitis, and vaginitis. Which of the following fungal pathogens is MOST likely responsible for these conditions?
- Pneumocystis jirovecii
- Candida albicans (correct)
- Cryptococcus neoformans
- Aspergillus fumigatus
A lung biopsy from an immunocompromised patient reveals septate hyphae with acute-angle branching. Which fungal pathogen is the MOST likely cause?
A lung biopsy from an immunocompromised patient reveals septate hyphae with acute-angle branching. Which fungal pathogen is the MOST likely cause?
An AIDS patient (CD4 < 200) presents with pneumonia. A silver stain of the lung tissue is positive. Which fungal pathogen is MOST likely responsible?
An AIDS patient (CD4 < 200) presents with pneumonia. A silver stain of the lung tissue is positive. Which fungal pathogen is MOST likely responsible?
A patient who recently spent time in Latin America develops a lung infection, which then disseminates to the mucosa, skin, and lymph nodes. Microscopic examination reveals yeast cells with multiple buds resembling a 'pilot wheel'. Which fungal pathogen is the MOST likely cause?
A patient who recently spent time in Latin America develops a lung infection, which then disseminates to the mucosa, skin, and lymph nodes. Microscopic examination reveals yeast cells with multiple buds resembling a 'pilot wheel'. Which fungal pathogen is the MOST likely cause?
Which mechanism of action describes how azole antifungals combat fungal infections?
Which mechanism of action describes how azole antifungals combat fungal infections?
Following a natural disaster involving significant flooding, several patients present with severe necrotic skin lesions and signs of systemic infection. Cultures reveal non-septate hyphae with right-angle branching. Which of the following genera of fungi is MOST likely responsible for these infections?
Following a natural disaster involving significant flooding, several patients present with severe necrotic skin lesions and signs of systemic infection. Cultures reveal non-septate hyphae with right-angle branching. Which of the following genera of fungi is MOST likely responsible for these infections?
Why is flucytosine typically administered in conjunction with amphotericin B when treating Cryptococcus meningitis?
Why is flucytosine typically administered in conjunction with amphotericin B when treating Cryptococcus meningitis?
A patient presents with a suspected systemic fungal infection. Initial treatment with amphotericin B is considered. What critical factor should be evaluated before administering this medication?
A patient presents with a suspected systemic fungal infection. Initial treatment with amphotericin B is considered. What critical factor should be evaluated before administering this medication?
How do echinocandins such as caspofungin inhibit fungal growth, and against which specific fungi are they most effective?
How do echinocandins such as caspofungin inhibit fungal growth, and against which specific fungi are they most effective?
A patient is diagnosed with a dermatophyte infection affecting the nails. Which antifungal agent, administered orally, is most appropriate for treating this condition?
A patient is diagnosed with a dermatophyte infection affecting the nails. Which antifungal agent, administered orally, is most appropriate for treating this condition?
Aflatoxins are associated with which of the following health risks and food sources?
Aflatoxins are associated with which of the following health risks and food sources?
How do trichothecenes exert their toxic effects, and in what types of food products are they typically found?
How do trichothecenes exert their toxic effects, and in what types of food products are they typically found?
The term 'opportunistic mycoses' refers to fungal infections that primarily affect immunocompromised individuals. Which mechanism primarily leads to these infections?
The term 'opportunistic mycoses' refers to fungal infections that primarily affect immunocompromised individuals. Which mechanism primarily leads to these infections?
What is the primary immunological mechanism underlying hypersensitivity pneumonitis, and what are some representative causative agents and diseases?
What is the primary immunological mechanism underlying hypersensitivity pneumonitis, and what are some representative causative agents and diseases?
Flashcards
Polyenes (Amphotericin B, Nystatin)
Polyenes (Amphotericin B, Nystatin)
Bind to ergosterol, disrupting the fungal membrane and causing pore formation.
Echinocandins (Caspofungin)
Echinocandins (Caspofungin)
Inhibit β-glucan synthesis, disrupting the fungal cell wall.
Flucytosine
Flucytosine
Converted to 5-FU inside fungi, inhibiting DNA/RNA synthesis.
Terbinafine
Terbinafine
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Aflatoxins
Aflatoxins
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Ochratoxins
Ochratoxins
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Trichothecenes
Trichothecenes
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Hypersensitivity Pneumonitis
Hypersensitivity Pneumonitis
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Systemic Mycoses
Systemic Mycoses
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Histoplasma capsulatum
Histoplasma capsulatum
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Blastomyces dermatitidis
Blastomyces dermatitidis
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Coccidioides immitis
Coccidioides immitis
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Paracoccidioides brasiliensis
Paracoccidioides brasiliensis
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Opportunistic Mycoses
Opportunistic Mycoses
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Candida albicans
Candida albicans
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Azoles
Azoles
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Study Notes
- Fungal infections are categorized into systemic mycoses, opportunistic mycoses, mycotoxicoses, and hypersensitivity reactions.
Systemic Mycoses (Dimorphic Fungi)
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Systemic mycoses are caused by dimorphic fungi and typically start with a lung infection after inhaling spores from the soil.
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Histoplasma capsulatum
- Causes lung infection that can spread to the liver, spleen, and bone marrow, especially in immunocompromised individuals.
- Characterized by intracellular yeast inside macrophages.
- Transmission occurs through the inhalation of spores found in bird or bat droppings, often in caves, soil, or demolition sites.
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Blastomyces dermatitidis
- Causes lung infection that can spread to the skin and bones.
- Features broad-based budding yeast.
- Transmitted via inhalation of spores from soil, decaying wood, or river valleys.
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Coccidioides immitis
- Inhaled arthroconidia turn into spherules filled with endospores in the lungs, leading to Valley fever.
- Transmission occurs through the inhalation of spores in desert soil, dust storms, or earthquake-prone areas.
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Paracoccidioides brasiliensis
- Characterized by multiple budding yeast, resembling a "pilot wheel."
- Causes lung infection that can spread to the mucosa, skin, and lymph nodes.
- Transmission occurs through inhalation, commonly in Latin America.
Opportunistic Mycoses
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Opportunistic mycoses predominantly affect immunocompromised individuals and are typically contracted through inhalation or endogenous overgrowth.
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Candida albicans
- It is a normal flora of the skin, GI tract, and genital tract; it can cause thrush, esophagitis, vaginitis, and candidemia in immunocompromised individuals due to overgrowth.
- Forms germ tubes at 37°C.
- Transmission is endogenous, resulting from overgrowth in immunosuppressed individuals.
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Aspergillus fumigatus
- Features septate hyphae with acute-angle branching.
- Causes fungus balls in pre-existing lung cavities or invasive aspergillosis in immunocompromised individuals.
- Transmission occurs through inhalation of spores from decaying vegetation, air ducts, or compost.
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Cryptococcus neoformans
- Characterized by a capsulated yeast, which is India Ink positive.
- Causes meningitis, especially in AIDS patients.
- Transmission occurs through inhalation of spores from pigeon droppings or soil.
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Pneumocystis jirovecii
- Causes opportunistic pneumonia in AIDS patients with CD4 counts below 200.
- Stains positive with silver stain.
- Transmission occurs person-to-person via airborne routes.
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Mucor & Rhizopus spp.
- Features non-septate hyphae with right-angle branching.
- Invades blood vessels, leading to necrosis, which manifests as black eschar.
- Transmission occurs through inhalation of spores from bread mold or decaying organic matter.
Antifungal Agents
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Antifungal drugs target ergosterol synthesis, fungal cell wall synthesis, or DNA synthesis.
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Azoles (Fluconazole, Itraconazole, Voriconazole)
- They inhibit ergosterol synthesis by inhibiting lanosterol 14-α-demethylase.
- Used against Candida, Cryptococcus, Aspergillus, and dermatophytes.
- Administered orally or intravenously.
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Polyenes (Amphotericin B, Nystatin)
- Binds to ergosterol, disrupting the fungal membrane by forming pores.
- Amphotericin B is used for systemic infections, while Nystatin is used topically for oral thrush.
- Amphotericin B is administered intravenously, while Nystatin is applied topically.
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Echinocandins (Caspofungin, Micafungin, Anidulafungin)
- Inhibit β-glucan synthesis, which is essential for fungal cell wall synthesis.
- Used for Candida and Aspergillus infections.
- Administered intravenously only.
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Flucytosine
- It is converted to 5-FU inside fungi, inhibiting DNA and RNA synthesis.
- Used in combination with Amphotericin B for Cryptococcus meningitis.
- Administered orally.
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Terbinafine
- Inhibits squalene epoxidase, blocking ergosterol synthesis.
- Used for dermatophyte infections of the nails, skin, and hair.
- Administered orally or topically.
Mycotoxicoses & Hypersensitivity
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Mycotoxicoses involve toxic metabolites produced by fungi, while hypersensitivity involves allergic reactions to fungal spores.
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Aflatoxins (Aspergillus spp.)
- Are hepatotoxic and carcinogenic, linked to hepatocellular carcinoma.
- Found in contaminated grains, nuts, and milk.
- Transmission occurs through ingestion of contaminated food.
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Ochratoxins (Aspergillus, Penicillium spp.)
- Are nephrotoxic and hepatotoxic.
- Found in grains, coffee, and wine.
- Transmission occurs through ingestion.
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Trichothecenes (Fusarium spp.)
- Are cytotoxic and immunosuppressive.
- Found in contaminated cereals.
- Transmission occurs through ingestion or inhalation.
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Hypersensitivity Pneumonitis
- It is an allergic reaction to inhaled fungal spores, molds, and thermophilic actinomycetes.
- Causes farmer’s lung and bird fancier’s lung.
- Transmission occurs through inhalation.
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Description
Systemic mycoses are fungal infections caused by dimorphic fungi. The infection typically starts in the lungs after inhaling spores. Examples include Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis.
