Lecture 13 and 14 Mycology Intro

Question 1

What are fungi and name some general properties of fungi

Answer 1

Fungi are eukarya which obtain energy from breakdown of dead or living organic matter. They have a nucleus and their cell walls contain cellulose and chitin

Question 2

What are the 4 features of fungi

Answer 2

Capsules - slime layers which protect from phagocytosis
Cell wall - polysaccharide microfibrils which determine fungal morphology
Cytoplasmic membrane - bilayered membrane containing ergosterol
Hyphae - Branching filaments either septated or non-septated

Question 3

What are the three mechanisms of asexual reproduction

Answer 3

Sporulation/germination - forming of spores to grow
Budding of yeast cells
Fragementation of hypahe

Question 4

Describe the two types of spores

Answer 4

Disperal spores - macro/micro conidia, produced in large numbers dispersed by conidiophores and are ready to be germinated in available nutrients
Survival spores - large spores (chlamydospore), germination only occurs when a stimuli occurs or after a long dormancy

Question 5

What are the three mechanisms of fungal disease?

Answer 5

1. tissue invasion (mycosis)
2. toxin production (mycotoxicosis)
3. induction of hypersensitivity

Question 6

What is mycoses?

Answer 6

Infection which can be either cutaneous or non-cutaneous. Can occur via pathogenitic fungi (ringworm) where the host is healthy or by opportunistic fungi (aspergillus) which requires an immunocompromised host.

Question 7

What are the routes of entry for a fungal infection (6)

Answer 7

1. Respiratory (nasal passages)
2. Wounds
3. Mucous membranes
4. Skin
5. Endogenous commensals
6. Exogenous fungal spores

Question 8

What are the 6 barriers for fungal infection

Answer 8

1. Physical barriers (skin, cilia)
2. Chemical barriers (secretions)
3. Innate immunity (phagocytes)
4. Acquired immunity (cell-mediated immunity)
5. Body temperature
6. Oxygen

Question 9

Describe the 4 Invasion patterns of fungal infection

Answer 9

1. Superficial mycoses (infection is mild and contagious)
2. Subcutaneous mycoses (secondary to trauma)
3. Granulomas
4. Systemic mycoses (respiratory systems, infection is severe)

Question 10

Describe mycotoxicosis

Answer 10

Release of mycotoxins which are secondary metabolites of toxigenic fungi. These contaminate crops or stored food. Exposure to mycotoxins is non-antigenic and can be either an endogenous toxin or exogenous toxin.

Question 11

Describe yeasts and give two medically important examples

Answer 11

Yeasts are unicellular eukarya which are facultatively anaerobic. They reproduce by budding and can be in low numbers on the skin. Candida albicans and cryptococcus neoformans are two medically important yeasts.

Question 12

Describe moulds and give two medically important examples

Answer 12

Moulds are strict aerobes which produce hyphae, growth occurs at the tips of the hyphae. Aspergillus and penicillium spp. are important moulds

Question 13

Describe dimorphic fungi and give two medically important examples

Answer 13

Dimorphic fungi are fungi which can exist as yeasts at 37 degrees and moulds at 25 degrees. Dimorphic fungi are completely pathogenic. Blastomyces and histoplasma are important dimorphic fungi.

Question 14

What are hypersensitivity reactions

Answer 14

Fungal induction of hypersensitivity – immune

complex-induced tissue injury (Type 3 hypersensitivity). Usually related to spores