Lecture 19: Fungi III

Question 1

Are spores haploid or diploid?

Answer 1

Spores are overall haploid, but they can spend some time as diploids during their sexual reproduction cycle.

Question 2

What are the 3 mechanisms by which fungi can cause disease?

Answer 2

1. Inappropriate immune responses
2. Infections
3. Mycotoxins

Question 3

Inappropriate immune responses due to fungi are called _____.

Answer 3

Hypersensitivity

Question 4

Explain how fungi can evoke a hypersensitivity response.

Answer 4

They evoke the release of IgE fungal antigens, which causes mast cell degranulation and histamine release.

Question 5

Give 4 examples of hypersensitivity responses.

Answer 5

Asthma, rhinitis, pneumonitis, and sinusitis

Question 6

Name an example of a fungus that can cause hypersensitivity reactions.

Answer 6

Aspergillus

Question 7

What is the typical cause of uncomplicated asthma? It is treatable?

Answer 7

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.

Question 8

What is the typical cause of allergic bronchopulmonary aspergillosis?

Answer 8

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.

Question 9

An example of an aspergillus allergic disease is […] (2 names)

Answer 9

Farmer’s lung, extrinsic alveolities

Question 10

Explain how farmer’s lung works.

Answer 10

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.

Question 11

What is mycosis?

Answer 11

A fungal infection of the body.

Question 12

Are mycoses generally acute or chronic? Why?

Answer 12

They are generally chronic, as fungi grow slowly.

Question 13

Are mycoses easy or difficult to treat? Why?

Answer 13

They are difficult to treat, because fungi are close to animals and share a lot of similarities.

Question 14

What are the 3 major categories of mycoses?

Answer 14

Superficial, subcutaneous, and systemic.

Question 15

What are the defining characteristics of superficial mycoses?

Answer 15

They are common, benign, and can infect immunocompetent individuals.

Question 16

What are the defining characteristics of subcutaneous mycoses?

Answer 16

They affect deeper layers of skin than superficial mycoses. They are more dangerous than superficial but less dangerous than systemic.

Question 17

What are the defining characteristics of systemic mycoses?

Answer 17

They are less common, severe (often lethal if left untreated), and primarily affect the elderly or immunocompromised.

Question 18

Systemic mycoses are […] pathogens, because […]

Answer 18

Opportunistic, because they take the opportunity to infect immunocompromised people.

Question 19

Superficial mycoses are caused by what type of fungi? From which phylum?

Answer 19

Dematophytes (dermatomycoses), from phylum Ascomycota.

Question 20

Dermatophytes infect what parts of the body?

Answer 20

Hair, skin, or nails (surface layers only)

Question 21

Athlete’s foot is an example of what kind of infection?

Answer 21

Superficial mycosis.

Question 22

Athlete’s foot is called by the fungi […]

Answer 22

Trichophyton

Question 23

Can superficial mycoses be treated? How?

Answer 23

Yes, by antifungal creams or medication.

Question 24

Subcutaneous mycoses come from what kinds of fungi?

Answer 24

Fungi that inhabit the soil.

Question 25

Sporotrichosis disease is what kind of infection?

Answer 25

Subcutaneous mycosis.

Question 26

Sporotrichosis disease is caused by what fungus? From what phylum?

Answer 26

Sporothrix schenkii, a dimorphic fungus from phylum ascomycota.

Question 27

Explain how sporothrix schenkii infects the body.

Answer 27

It enters through a wound and then forms a small ulcer.

Question 28

Systemic mycoses are typically caused by what types of fungi?

Answer 28

Mainly yeasts and dimorphic fungi that live in soil.

Question 29

How do humans become infected by systemic mycoses?

Answer 29

By inhaling spores.

Question 30

Give 4 examples of systemic mycoses.

Answer 30

Histoplasmosis, blastomycosis, cryptococcosis, candidiasis

Question 31

Name 4 predisposing conditions for systemic fungal infections.

Answer 31

Impaired immune system, pregnancy, antibiotic use, and age

Question 32

How can antibiotic use affect vulnerability to systemic mycoses?

Answer 32

Antibiotic use disrupts the normal microbiota, which can lead to fugal overgrowth and infection.

Question 33

What are the main 3 categories of fungi that cause invasive fungal diseases?

Answer 33

Yeasts, dimorphic fungi, and (some molds)

Question 34

What fungus (name and type) causes candidiasis?

Answer 34

It is caused by the overgrowth of Candida albicans, a yeast.

Question 35

In candidiasis, what is the effect of the fungus on the body?

Answer 35

The Candida albicans forms pseudohyphae, making it resistant to phagocytosis.

Question 36

Where does candidiasis occur?

Answer 36

In the skin and mucous membranes of the genitourinary tract and mouth.

Question 37

What is thrush?

Answer 37

It is a case of candidiasis where C. albicans infects the oral cavity.

Question 38

What is the cause of candidiasis (2)?

Answer 38

It results when antibiotics suppress competing bacteria or a change occurs in the mucosal pH that is favourable to fungi.

Question 39

What type of fungus is candida albicans? How does it grow?

Answer 39

It is a yeast that grows using pseudohyphae.

Question 40

In candida albicans, [...] is required for virulence.

Answer 40

Morphological switching.

Question 41

What is distinctive about the sexual cycle of C. albicans?

Answer 41

The diploid fungi combines to form tetraploids, which can affect virulence. The chromosomes then shed over time to return to diploid form.

Question 42

What is candida auris? How does it work?

Answer 42

It is another Candida yeast that starts by colonizing the skin, then enters the organs and the blood stream.

Question 43

Why is Candida auris such a major health risk?

Answer 43

It is multi-drug resistant, making its infections very difficult to treat.

Question 44

What type of fungus is cryptococcus?

Answer 44

It is an encapsulated yeast.

Question 45

Describe the sexual cycle type and phylum of crytococcus.

Answer 45

It is heterothallic and is a basidiomycete

Question 46

What are the 2 common species of cryptococcus?

Answer 46

Neoforms and gatti

Question 47

What environments are cryptococcus found in?

Answer 47

Soil, particularly associated with bird droppings in the case of neoformans, and eucalyptus trees.

Question 48

How do individuals get infected with cryptococcus?

Answer 48

They inhale yeast cells or basidiospores.

Question 49

What are the typical symptoms of C. neoformans?

Answer 49

It often presents as chronic meningitis, and is typically associated with HIV disease or other immune deficiency.

Question 50

What are the 3 virulence factors of cryptococcus? Explain the function of each.

Answer 50

Capsule: inhibits phagocytosis Thermotolerance: permits growth in CSF Melanin: antioxidant, resists phagocyte killing

Question 51

What is the source of cryptococcus gatti?

Answer 51

It came from Vancouver island and was first seen in marine mammals.

Question 52

How does cryptococcus gatti affect its host?

Answer 52

It causes pneumonia and meningitis IN IMMUNOCOMPETENT patients. It also infects native trees and soils.

Question 53

Name the 2 systemic diseases that are caused by yeasts.

Answer 53

Candidiasis and cryptococcus

Question 54

Name 3 systemic diseases caused by dimorphic fungi.

Answer 54

Histoplasmosis, coccidioidomycosis, blastomycosis

Question 55

Dimorphic fungi grow as mold in [...] and as yeast in [...]

Answer 55

Soil, humans

Question 56

What type of individuals do yeast systemic infections affect?

Answer 56

Immunocompromised individuals

Question 57

What types of individuals do dimorphic fungi infect?

Answer 57

They can infect immunocompetent individuals

Question 58

What fungus causes histoplasmosis?

Answer 58

Histoplasma capsulatum, a dimorphic fungus.

Question 59

How does histoplasma capsulatum affect the body?

Answer 59

It grows intracellularly in macrophages

Question 60

Where is histoplasmosis acquired?

Answer 60

Spores are acquired in areas with bird or bat droppings.

Question 61

What is the main symptom of histoplasmosis?

Answer 61

Lung lesions

Question 62

What is the geographical range of histoplasmosis?

Answer 62

It is limited to central-eastern USA

Question 63

What is another name for coccidioidomycosis?

Answer 63

Valley fever/San Joaquin fever

Question 64

What fungus causes coccidioidomycosis?

Answer 64

Coccidioides immitis, a dimorphic fungus

Question 65

What is the geographic range of coccidioidomycosis?

Answer 65

It is found in alkaline desert soils in the American southwest.

Question 66

What are the symptoms of a coccidioidomycosis infection?

Answer 66

Fever, coughing, weight loss

Question 67

What fungus causes blastomycosis?

Answer 67

Blastomyces dermatitidis, a dimorphic fungus

Question 68

Where does the fungus responsible for blastomycosis grow?

Answer 68

On soil in forests - associated with rotting wood

Question 69

What are the symptoms of blastomycosis?

Answer 69

Cutaneous abcesses, extensive tissue damage. It is hard to distinguish from histoplasmosis.

Question 70

What individuals are most affected by blastomycosis?

Answer 70

Dogs

Question 71

What respiratory disease do aspergillus fumigatus case? Where do they grow?

Answer 71

Aspergillosis. The conidia grow in compost piles

Question 72

Name 2 other fungi than aspergillus involved in respiratory disease that are neither yeasts nor dimorphic fungi.

Answer 72

Rhizopus and Mucor

Question 73

Name 3 predisposing factors to respiratory disease.

Answer 73

Immunocompromised state, cancer, diabetes (when insulin not taken)