Mycology

Question 1

What are the main features of fungi?

Answer 1

• eukaryotic
• uni or multicellular
• mostly reproduce asexually (mitosis)
• monomorphic, dimorphic or polymorphic

Question 2

What are the main components of fungi exteriors?

Answer 2

• rigid cell wall: chitin, glucans, mannoproteins

- cytoplasmic membrane: phospholipid bilayer w ergosterol

Question 3

What are the 3 major classes of fungi?

Answer 3

• yeasts
• moulds
• dimorphic fungi (yeast and mould–> depends on temp, nutrietns, CO2)

Question 4

What are the roles of aerial and vegetative hyphae in moulds (mycelium)?

Answer 4

aerial hyphae: support for reproductive structures

vegetative hyphae: provides nutrients to aerial hyphae

Question 5

For dimorphic fungi, when are they seen in yeast form versus mould form?
(Hint: Temperature differential)

Answer 5

yeast form: in vivo or 37deg c.

mould form; 22-25 deg c.

Question 6

List dimorphic fungi examples:

Answer 6

• Blastomyces dermatitidis *
• Histoplasma capsulatum *
• Sporothrix schenkii*
• Coccidioides immitis
• Paracoccidioides brasiliensis
• Penicillium marneffei

*endemic in Canada

Question 7

What immune reactions are critical in eliminating fungi?

Answer 7

-nonspecific inflammatory reactions…esp neutrophil phagocytosis and killing.

Question 8

Who is at increased risk of fungal infection that does not clear?

Answer 8

1. Patients with depressed neutrophil function/number:

• chemotherapy patients
• disorders of neutrophil funx: chronic granulomatous disease

2. Patients with depressed CMI (cell-mediated immunity):
   - HIV

Question 9

What are the 4 classifications of fungal infections (location):

Answer 9

1. mucocutaenous
2. superficial
3. subcutaneous
4. systemic

Question 10

What is the most common mucocutaneous fungal infection?

What are the favourable conditions for these?

Answer 10

1. C. albicans
2. -moisture + warmth
   - disruption of normal flora (ABs)
   - diminished neutrophil phagocytosis and killing
   - diminished cell-mediated immunity

Question 11

What type of fungi typically cause superficial fungal infections?

Answer 11

Dermatophytoses

ex. Ringworm or Tinea (refers to serpentine lesion)

Question 12

What do dermatophytoses use as nutrient source?

What enzyme do they use to do so?

Answer 12

• keratin

- keratinase

Question 13

What are the 3 main epidemiological groups of superficial fungi?

Answer 13

1. Geophilic (soil) ex. Microsporum gypseum
2. Zoophilic (parasitic on animals) ex. Microsporum canis
3. Anthropophilic (humans) ex. Trichosporon rubrum

Question 14

What are the 3 main genera of dermatophytes?

Answer 14

1. Trichophyton
2. Epidermophyton
3. Microsporum

Question 15

Name a common superficial fungal infection:

What is it caused by?

Answer 15

-Tinea versicolor (Pityriasis versicolor)

caused by Malassezia furfur

Question 16

What are the 2 common classes of subcutaneous mycetoma?

What population does it effect most often?

Answer 16

1. Chromoblastomycosis (caused by ‘black moulds’ in soil)
2. Mycetoma (caused by black moulds and fungus-like bacteria)
   - effects barefooted populations in Tropics

Question 17

List systemic fungal infections:

Answer 17

• Blastomyces dermatitidis (Blastomycosis)- Ontario + Manitoba
• Coccidioides immitis (Coccidioidomycosis)
• Histoplasma capsulatum (Histoplasmosis)
• Paracoccidioides brasiliensis (Paracoccidioimycosis)

Question 18

List the characteristics of dimorphic fungi:

Answer 18

• geographically restricted
• produce asymptomatic to severe life threatening disseminated disease
• primary lung infx +/- dissemination
• soil organisms
• infect normal and immunocompromised hosts

Question 19

List 3 opportunistic mycoses:

Answer 19

1. Candida albicans (Candidiasis)
2. Cryptococcus neoformans (Cryptococcosis)
3. Aspergillus species (Aspergillosis)