Fungi

Question 1

What is a primary pathogen?

Answer 1

Pathogen that can cause disease in anybody.

Question 2

What is an opportunistic pathogen?

Answer 2

Pathogen that causes disease in the immunocompromised but has low pathogenicity in all other demographics.

Question 3

What are 2 characteristic substances found in cell walls of fungi?

Answer 3

Chitin & ergosterol.

Question 4

Why is chitin important?

Answer 4

It stains white with calcium binding agents so we can identify fungi in clinical specimens very easily.

Question 5

Why is ergosterol important?

Answer 5

Humans have cholesterol in our cell membranes, so ergosterol will differentiate fungal cells from human cells. Many antifungal agents target ergosterol synthesis.

Question 6

What are the 3 important fungi to remember?

Answer 6

Molds, yeasts & thermally dimorphic fungi.

Question 7

What is the body of a mould called?

Answer 7

The thallus.

Question 8

What are the 2 types of hyphae?

Answer 8

Coenocytic & septate.

Question 9

What is the difference between coenocytic hyphae and septate hyphae?

Answer 9

Septate hyphae have many nuclei that are separated by septations. Coenocytic hyphae have many nuclei that lack septations.

Question 10

Most moulds are ________ _______, while most yeasts are _____________ ________ which is important for invasiveness.

Answer 10

obligate aerobes, facultatively anaerobic.

Question 11

The shape of yeast is _____/_________ - it looks like _______ bacteria.

Answer 11

oval/spherical, larger.

Question 12

How do yeasts reproduce?

Answer 12

Budding.

Question 13

What happens when the buds of yeast fail to detach?

Answer 13

They form pseudohyphae.

Question 14

Saccharomyces is a ___-_________ yeast used for cooking, baking & fermentation.

Answer 14

non-pathogenic.

Question 15

What is the most common yeast causing human infections?

Answer 15

Candida albicans.

Question 16

Why are yeasts generally more invasive to the human body than moulds are?

Answer 16

Yeasts are facultatively anaerobic, so they can survive in areas of our body that have anaerobic environments.

Question 17

What is the virulence factor of Cryptococcus neoformans?

Answer 17

Polysaccharide capsule.

Question 18

What are the 2 forms of growth for thermally dimorphic fungi & at what temperature does each form occur at?

Answer 18

Mould @ 20ºC.

Yeast @ 37ºC (body temp).

Question 19

Thermally dimorphic fungi are always _______ pathogens.

Answer 19

primary.

Question 20

Are infections by thermally dimorphic fungi infections from person-to-person? Why or why not?

Answer 20

No, the mould form can only be spread by spores in the air.

Question 21

Describe the pathogenicity of Sporothrix (Rose Gardener’s Disease).

Answer 21

Fungal spores introduced into wound after trauma → enter bloodstream → reach lymph nodes & cause lymphangitis.

Question 22

What are fungal “spores” technically called?

Answer 22

Conidia.

Question 23

Fungi are generally ____ nutritionally demanding than bacteria & grow ______ than bacteria in extreme conditions.

Answer 23

less, better.

Question 24

What are all fungal diseases called?

Answer 24

Mycoses.

Question 25

What are the 3 types of fungal disease, from most to least severe?

Answer 25

Systemic (most), cutaneous, superficial (least).

Question 26

What are dermatophytes & what level of fungal infection do they cause?

Answer 26

Dermatophytes degrade keratin & use it as food. They cause cutaneous infections like athlete’s foot/ringworm.

Question 27

What are 2 examples of opportunistic fungal pathogens that are abundant in the environment/in our bodies but will cause severe infections in the immunocompromised?

Answer 27

Aspergillus sp. (causes aspergillosis) & Candida albicans (causes candidiasis).