Lecture 19: Fungi III Flashcards
Are spores haploid or diploid?
Spores are overall haploid, but they can spend some time as diploids during their sexual reproduction cycle.
What are the 3 mechanisms by which fungi can cause disease?
- Inappropriate immune responses
- Infections
- Mycotoxins
Inappropriate immune responses due to fungi are called _____.
Hypersensitivity
Explain how fungi can evoke a hypersensitivity response.
They evoke the release of IgE fungal antigens, which causes mast cell degranulation and histamine release.
Give 4 examples of hypersensitivity responses.
Asthma, rhinitis, pneumonitis, and sinusitis
Name an example of a fungus that can cause hypersensitivity reactions.
Aspergillus
What is the typical cause of uncomplicated asthma? It is treatable?
It is usually due to sensitization to conidial antigens of Aspergillus. The IgEs and histamine cause the airways to tighten. It is usually controllable with medication.
What is the typical cause of allergic bronchopulmonary aspergillosis?
It necessitates a pre-existing airway disease such as cystic fibrosis. It introduces large quantities of the IgE to fight hyphal antigens, which can be lethal.
An example of an aspergillus allergic disease is […] (2 names)
Farmer’s lung, extrinsic alveolities
Explain how farmer’s lung works.
It requires the inhalation of decomposing hay, which has high quantities of thermophilic bacteria and fungi. These antigens can cause pneumonia (IMPORTANT) and the tightening of the airways.
What is mycosis?
A fungal infection of the body.
Are mycoses generally acute or chronic? Why?
They are generally chronic, as fungi grow slowly.
Are mycoses easy or difficult to treat? Why?
They are difficult to treat, because fungi are close to animals and share a lot of similarities.
What are the 3 major categories of mycoses?
Superficial, subcutaneous, and systemic.
What are the defining characteristics of superficial mycoses?
They are common, benign, and can infect immunocompetent individuals.
What are the defining characteristics of subcutaneous mycoses?
They affect deeper layers of skin than superficial mycoses. They are more dangerous than superficial but less dangerous than systemic.
What are the defining characteristics of systemic mycoses?
They are less common, severe (often lethal if left untreated), and primarily affect the elderly or immunocompromised.
Systemic mycoses are […] pathogens, because […]
Opportunistic, because they take the opportunity to infect immunocompromised people.
Superficial mycoses are caused by what type of fungi? From which phylum?
Dematophytes (dermatomycoses), from phylum Ascomycota.
Dermatophytes infect what parts of the body?
Hair, skin, or nails (surface layers only)
Athlete’s foot is an example of what kind of infection?
Superficial mycosis.
Athlete’s foot is called by the fungi […]
Trichophyton
Can superficial mycoses be treated? How?
Yes, by antifungal creams or medication.
Subcutaneous mycoses come from what kinds of fungi?
Fungi that inhabit the soil.
Sporotrichosis disease is what kind of infection?
Subcutaneous mycosis.
Sporotrichosis disease is caused by what fungus? From what phylum?
Sporothrix schenkii, a dimorphic fungus from phylum ascomycota.
Explain how sporothrix schenkii infects the body.
It enters through a wound and then forms a small ulcer.
Systemic mycoses are typically caused by what types of fungi?
Mainly yeasts and dimorphic fungi that live in soil.
How do humans become infected by systemic mycoses?
By inhaling spores.
Give 4 examples of systemic mycoses.
Histoplasmosis, blastomycosis, cryptococcosis, candidiasis
Name 4 predisposing conditions for systemic fungal infections.
Impaired immune system, pregnancy, antibiotic use, and age
How can antibiotic use affect vulnerability to systemic mycoses?
Antibiotic use disrupts the normal microbiota, which can lead to fugal overgrowth and infection.
What are the main 3 categories of fungi that cause invasive fungal diseases?
Yeasts, dimorphic fungi, and (some molds)
What fungus (name and type) causes candidiasis?
It is caused by the overgrowth of Candida albicans, a yeast.
In candidiasis, what is the effect of the fungus on the body?
The Candida albicans forms pseudohyphae, making it resistant to phagocytosis.
Where does candidiasis occur?
In the skin and mucous membranes of the genitourinary tract and mouth.
What is thrush?
It is a case of candidiasis where C. albicans infects the oral cavity.
What is the cause of candidiasis (2)?
It results when antibiotics suppress competing bacteria or a change occurs in the mucosal pH that is favourable to fungi.
What type of fungus is candida albicans? How does it grow?
It is a yeast that grows using pseudohyphae.
In candida albicans, […] is required for virulence.
Morphological switching.
What is distinctive about the sexual cycle of C. albicans?
The diploid fungi combines to form tetraploids, which can affect virulence. The chromosomes then shed over time to return to diploid form.
What is candida auris? How does it work?
It is another Candida yeast that starts by colonizing the skin, then enters the organs and the blood stream.
Why is Candida auris such a major health risk?
It is multi-drug resistant, making its infections very difficult to treat.
What type of fungus is cryptococcus?
It is an encapsulated yeast.
Describe the sexual cycle type and phylum of crytococcus.
It is heterothallic and is a basidiomycete
What are the 2 common species of cryptococcus?
Neoforms and gatti
What environments are cryptococcus found in?
Soil, particularly associated with bird droppings in the case of neoformans, and eucalyptus trees.
How do individuals get infected with cryptococcus?
They inhale yeast cells or basidiospores.
What are the typical symptoms of C. neoformans?
It often presents as chronic meningitis, and is typically associated with HIV disease or other immune deficiency.
What are the 3 virulence factors of cryptococcus? Explain the function of each.
Capsule: inhibits phagocytosis
Thermotolerance: permits growth in CSF
Melanin: antioxidant, resists phagocyte killing
What is the source of cryptococcus gatti?
It came from Vancouver island and was first seen in marine mammals.
How does cryptococcus gatti affect its host?
It causes pneumonia and meningitis IN IMMUNOCOMPETENT patients. It also infects native trees and soils.
Name the 2 systemic diseases that are caused by yeasts.
Candidiasis and cryptococcus
Name 3 systemic diseases caused by dimorphic fungi.
Histoplasmosis, coccidioidomycosis, blastomycosis
Dimorphic fungi grow as mold in […] and as yeast in […]
Soil, humans
What type of individuals do yeast systemic infections affect?
Immunocompromised individuals
What types of individuals do dimorphic fungi infect?
They can infect immunocompetent individuals
What fungus causes histoplasmosis?
Histoplasma capsulatum, a dimorphic fungus.
How does histoplasma capsulatum affect the body?
It grows intracellularly in macrophages
Where is histoplasmosis acquired?
Spores are acquired in areas with bird or bat droppings.
What is the main symptom of histoplasmosis?
Lung lesions
What is the geographical range of histoplasmosis?
It is limited to central-eastern USA
What is another name for coccidioidomycosis?
Valley fever/San Joaquin fever
What fungus causes coccidioidomycosis?
Coccidioides immitis, a dimorphic fungus
What is the geographic range of coccidioidomycosis?
It is found in alkaline desert soils in the American southwest.
What are the symptoms of a coccidioidomycosis infection?
Fever, coughing, weight loss
What fungus causes blastomycosis?
Blastomyces dermatitidis, a dimorphic fungus
Where does the fungus responsible for blastomycosis grow?
On soil in forests - associated with rotting wood
What are the symptoms of blastomycosis?
Cutaneous abcesses, extensive tissue damage. It is hard to distinguish from histoplasmosis.
What individuals are most affected by blastomycosis?
Dogs
What respiratory disease do aspergillus fumigatus case? Where do they grow?
Aspergillosis. The conidia grow in compost piles
Name 2 other fungi than aspergillus involved in respiratory disease that are neither yeasts nor dimorphic fungi.
Rhizopus and Mucor
Name 3 predisposing factors to respiratory disease.
Immunocompromised state, cancer, diabetes (when insulin not taken)
