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Questions and Answers
What is the primary structural component of the cell wall in fungi?
What is the primary structural component of the cell wall in fungi?
Which of the following statements is true about filamentous fungi?
Which of the following statements is true about filamentous fungi?
Which spores are produced endogenously within a sporangium?
Which spores are produced endogenously within a sporangium?
What type of fungus is characterized by pseudohyphae in its reproductive cycle?
What type of fungus is characterized by pseudohyphae in its reproductive cycle?
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What type of spores do filamentous fungi produce to aid in dispersal?
What type of spores do filamentous fungi produce to aid in dispersal?
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What characteristic of fungi helps them to survive extreme temperatures and UV light?
What characteristic of fungi helps them to survive extreme temperatures and UV light?
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What is the primary method of reproduction for yeast-like fungi?
What is the primary method of reproduction for yeast-like fungi?
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Which condition is NOT associated with fungal infections or effects?
Which condition is NOT associated with fungal infections or effects?
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Which type of fungi primarily invades the epidermis, hair, and nails but not the dermis?
Which type of fungi primarily invades the epidermis, hair, and nails but not the dermis?
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Which of the following infections involves the dermis and subcutaneous tissue?
Which of the following infections involves the dermis and subcutaneous tissue?
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What type of patient is particularly at risk for fungal infections due to compromised immunity?
What type of patient is particularly at risk for fungal infections due to compromised immunity?
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What is one of the key methods for examining fungal specimens?
What is one of the key methods for examining fungal specimens?
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Which substance class is used to inhibit fungal cell wall synthesis?
Which substance class is used to inhibit fungal cell wall synthesis?
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What is the function of Sabouraud dextrose agar in fungal culture?
What is the function of Sabouraud dextrose agar in fungal culture?
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What is the primary characteristic of fungi like Candida in healthy individuals?
What is the primary characteristic of fungi like Candida in healthy individuals?
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What organ is primarily affected by dimorphic fungi in immunocompromised patients?
What organ is primarily affected by dimorphic fungi in immunocompromised patients?
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What is a common manifestation of superficial Aspergillosis?
What is a common manifestation of superficial Aspergillosis?
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Which examination method can be used to identify C. albicans?
Which examination method can be used to identify C. albicans?
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What condition is characterized by the presence of a fungus ball in a preexisting lung cavity?
What condition is characterized by the presence of a fungus ball in a preexisting lung cavity?
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Which specimen examination method is used for diagnosing invasive Aspergillosis?
Which specimen examination method is used for diagnosing invasive Aspergillosis?
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What is a common risk factor for developing systemic infections from Aspergillus spp.?
What is a common risk factor for developing systemic infections from Aspergillus spp.?
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What symptom is least likely related to superficial Aspergillosis?
What symptom is least likely related to superficial Aspergillosis?
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The patient in the clinical case works as a grain inspector. What potential infection might he be particularly susceptible to?
The patient in the clinical case works as a grain inspector. What potential infection might he be particularly susceptible to?
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What is the key distinguishing feature observed when culturing A. fumigatus on SDA?
What is the key distinguishing feature observed when culturing A. fumigatus on SDA?
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Which of the following symptoms is least likely associated with superficial Aspergillosis?
Which of the following symptoms is least likely associated with superficial Aspergillosis?
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What is a primary risk factor for the development of invasive Aspergillosis in the clinical case presented?
What is a primary risk factor for the development of invasive Aspergillosis in the clinical case presented?
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Which method is used to directly identify the germ tube formation for C. albicans?
Which method is used to directly identify the germ tube formation for C. albicans?
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Which fungus is characterized by a greenish colony when cultured on SDA?
Which fungus is characterized by a greenish colony when cultured on SDA?
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What type of organism is Cryptococcus when referring to its potential for causing meningitis?
What type of organism is Cryptococcus when referring to its potential for causing meningitis?
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What is the identification method for Cryptococcal meningitis based on CSF examination?
What is the identification method for Cryptococcal meningitis based on CSF examination?
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Which of the following conditions describes a fungal infection occurring on a preexisting lung cavity?
Which of the following conditions describes a fungal infection occurring on a preexisting lung cavity?
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Which of the following specimens would be collected for diagnosing systemic lesions in a patient with suspected invasive Aspergillosis?
Which of the following specimens would be collected for diagnosing systemic lesions in a patient with suspected invasive Aspergillosis?
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What is the distinguishing feature of dimorphic fungi during their saprophytic phase?
What is the distinguishing feature of dimorphic fungi during their saprophytic phase?
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Which reproductive structure is formed within a sac called an ascus?
Which reproductive structure is formed within a sac called an ascus?
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What mechanism do fungi use to protect themselves from phagocytosis and extreme environments?
What mechanism do fungi use to protect themselves from phagocytosis and extreme environments?
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Which of the following is NOT a type of mycotoxicosis associated with fungal infections?
Which of the following is NOT a type of mycotoxicosis associated with fungal infections?
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In the lifecycle of filamentous fungi, what are the vegetative hyphae primarily responsible for?
In the lifecycle of filamentous fungi, what are the vegetative hyphae primarily responsible for?
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What type of reproduction occurs in the parasitic phase of filamentous fungi?
What type of reproduction occurs in the parasitic phase of filamentous fungi?
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What specific type of enzyme produced by fungi can contribute to tissue invasion?
What specific type of enzyme produced by fungi can contribute to tissue invasion?
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Which type of fungi primarily exists in soil and water habitats?
Which type of fungi primarily exists in soil and water habitats?
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Which type of fungi primarily causes infections in immunocompromised individuals by utilizing environmental spores?
Which type of fungi primarily causes infections in immunocompromised individuals by utilizing environmental spores?
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What is the purpose of using chloramphenicol and cycloheximide in Sabouraud dextrose agar cultivation?
What is the purpose of using chloramphenicol and cycloheximide in Sabouraud dextrose agar cultivation?
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Which fungal infection is characterized by the alteration of cytoplasmic membrane function as a treatment method?
Which fungal infection is characterized by the alteration of cytoplasmic membrane function as a treatment method?
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Which examination method is effective for detecting fungi in tissue biopsy specimens?
Which examination method is effective for detecting fungi in tissue biopsy specimens?
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Which of the following conditions is NOT typically a risk factor for developing fungal infections?
Which of the following conditions is NOT typically a risk factor for developing fungal infections?
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Which structure in fungi is primarily affected by drugs that inhibit ergosterol synthesis?
Which structure in fungi is primarily affected by drugs that inhibit ergosterol synthesis?
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What common feature is attributed to dimorphic fungi during culture?
What common feature is attributed to dimorphic fungi during culture?
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Which of the following species is a common cause of fungal meningitis in immunocompromised individuals?
Which of the following species is a common cause of fungal meningitis in immunocompromised individuals?
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Study Notes
Microbiology - General Mycology
- Mycology is the study of fungi
- Fungi are found in soil and water
- Fungi are eukaryotic organisms with a rigid cell wall made of chitin, glucans, mannans, and complex polysaccharides.
- Their cell membranes contain ergosterol.
- Some fungi are obligate aerobes, others are facultative anaerobes, and they can grow over a large range of temperatures and pH.
- Fungi can be classified as yeasts, yeast-like fungi, filamentous fungi, and dimorphic fungi.
Yeast and Yeast-like Fungi
- These fungi are round to oval and unicellular.
- They reproduce by budding or fission.
- Cryptococcus neoformans is an example.
- Candida is a yeast-like fungus that produces pseudohyphae.
Filamentous Fungi (Hyphae)
- Filamentous fungi are tubular, branched, and either septate or aseptate.
- Septate hyphae have cross-walls, while aseptate hyphae do not.
- Their branched hyphae create a mycelium.
- Vegetative hyphae are responsible for nutrient absorption.
- Aerial hyphae project above the colony.
- Aspergillus is an example of a filamentous fungus.
Dimorphic Fungi
- Dimorphic fungi can exist as either yeast or filamentous forms.
- Their form can change depending on the temperature and growth conditions.
- They are sometimes involved in human disease as a pathogenic organism.
Reproduction of Fungi
- Asexual reproduction is performed through mitosis by single parent.
- Spores are a form of asexual reproduction for specific species.
- Sporangiospores (endogenous) are formed inside sporangia.
- Conidiospores (exogenous) are formed externally.
- Arthrospores are a type of conidiospore.
- Sexual reproduction occurs through meiosis and involves specialized structures.
- Ascospores are formed inside asci (sacs).
- Basidiospores are formed on basidia.
Pathogenesis of Fungi
- Toxin production can alter physiology and invade tissues.
- Capsules can prevent phagocytosis.
- Enzymes phospholipases are produced to damage tissues.
- Fungi have thermo-tolerance and produce melanin to protect against extremes of temperature, and UV damage
- Biofilm formation can also contribute to the pathogenesis.
- Hypersensitivity can occur due to environmental exposure to fungal spores.
- Infections (mycoses) happen when fungi invade tissues and organs.
- Two types of toxicosis are mycotoxicosis (eating contaminated food) and mycetismus (eating preformed toxic mushrooms).
Harmful Effects of Fungi
- Fungi are responsible for plant diseases.
- Mycotoxins are produced by fungi and can cause illnesses in humans.
- Fungi cause food spoilage.
- Fungi can produce antibiotics, pigments, and dyes.
Diseases Caused by Fungi (Human Mycoses)
- Superficial mycoses affect the outermost layers of skin and hair.
- Cutaneous mycoses, involving the dermis, hair, and nails.
- Subcutaneous mycoses affect subcutaneous tissue including muscle, fascia.
- Opportunistic mycoses appear in immunocompromised patients.
- Systemic mycoses can spread to multiple organs through the bloodstream.
Laboratory Diagnosis of Fungal Diseases
- Specimens are collected according to the site and type of infection.
- Direct microscopy is a method using KOH, lactophenol cotton blue, or Gram stains.
- Direct immunofluorescence can also aid in diagnosis.
- Culture can be used to isolate fungi.
- SDA (Sabouraud dextrose agar) is a common culture medium for fungi. Fungi are grown on SDA at 25 degrees centigrade and 37 degrees centigrade to check for dimorphism. Macroscopic and microscopic examination and nucleic acid probe are crucial in the identification process.
Antifungal Agents
- Antifungal agents target fungal cells, which are eukaryotic.
- Many antifungals can be toxic to host cells.
- Mechanisms of inhibition include targeting cell wall synthesis, ergosterol synthesis, and nucleic acid synthesis.
- Antifungal agents include Polyenes, Azoles, Echinocandins, and Flucytosine which target different parts of the fungal cell.
Opportunistic Mycoses
- A group of mycoses that are caused by commensal or saprophytic fungi.
- They occur in immunocompromised individuals.
- Examples include cryptococcosis, candidiasis, and aspergillosis, and histoplasmosis.
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