Introduction to Fungi and Superficial Mycoses

Question 1

how do fungi reproduce?

Answer 1

sexual and asexual

Question 2

are molds multicellular or unicellular?

Answer 2

multicellular

Question 3

what does it mean that a fungus is monomorphic?

Answer 3

one form in environment and host

Question 4

what does it mean that a fungus is dimorphic?

Answer 4

two forms
triggered by temperature, CO2

Question 5

how long does fungus culture/growth in culture take?

Answer 5

days to weeks

Question 6

what are the five Ds of fungal diseases?

Answer 6

debilitating
destructive
difficult to diagnose
difficult to treat
do not have effective vaccines

Question 7

fungal diseases are ________________________, but not always

Answer 7

often opportunistic

Question 8

what are the host defenses against fungal infections?

Answer 8

intact skin and mucosal surfaces
low pH
antimicrobials
normal flora
mucus

Question 9

what does Dermatophytosis (ringworm) infect?

Answer 9

keratinized tissues: epidermis, hair, feather, claws

Question 10

what are the virulence factors of Dermatophytosis (ringworm)?

Answer 10

enzymes: keratinases digest keratin in skin, hair, nails, horn

Question 11

are Dermatophytes zoonotic?

Answer 11

yes

Question 12

what are the components of fungi cell walls?

Answer 12

chitin
ergosterol
beta-glucagon
cellulose

Question 13

what are the two morphologic forms of fungi?

Answer 13

molds
yeast

Question 14

how do yeasts reproduce sexually?

Answer 14

conjugation
rare

Question 15

what are hyphae?

Answer 15

mycelia
branching filaments: septate branches

Question 16

how do fungal cell walls stain with periodic acid schiff’s stain?

Answer 16

pink

Question 17

how do fungi stain with grocott’s methenamine silver stain?

Answer 17

black

Question 18

what are some monomorphic fungi?

Answer 18

Aspergillus spp: mold
Malassezia spp: yeast

Question 19

what is one dimorphic fungus?

Answer 19

Coccidioides immitis

Question 20

what types of diseases can dimorphic fungi cause?

Answer 20

deadly

Question 21

what is a polymorphic fungus?

Answer 21

Candida albicans

Question 22

what are the steps of germination for a mold?

Answer 22

spore swelling and increase in metabolic activity
formation of tubular projection
long growth leads to septa
formation of lateral branches
formation of mycelium (interlacing hyphae network)

Question 23

how are patients usually exposed to fungi?

Answer 23

environmental

Question 24

what host factors increase disease risk and severity?

Answer 24

prolonged antibiotics
immune compromise
very young/old
persistent moisture
co-morbidities

Question 25

what pathogen factors increase disease risk and severity?

Answer 25

dose
virulence factors
ability to invade or evade

Question 26

what is a fungi that infects nails and produces keratinocytes?

Answer 26

Onchomycosis

Question 27

what virulence factors help fungi survive inside the host?

Answer 27

capsule and cell wall: resist phagocytosis and low pH
enzymes: catalases, proteases
iron binding proteins

Question 28

are dermatophytoses primary pathogens or opportunistic?

Answer 28

primary pathogens

Question 29

what is the most common cause of animal candidiasis?

Answer 29

Candida albicans

Question 30

how do Candida spp lead to systemic spread?

Answer 30

vascular invasion by hyphae or pseudohyphae

Question 31

are Malassezia spp monomorphic, dimorphic, or polymorphic?

Answer 31

monomorphic

Question 32

what diseases do Malassezia spp cause?

Answer 32

otitis externa
dermatitis

Question 33

what opportunistic conditions lead to Malassezia spp causing disease?

Answer 33

moist skin
ear canal

Question 34

what are some associated conditions of Malassezia spp?

Answer 34

allergy
seborrheic dermatitis
bacterial dermatitis

Question 35

what are the virulence factors of Malassezia spp?

Answer 35

lipases
zymogens
proteases

Question 36

is ringworm a commensal?

Answer 36

no

Question 37

how can you diagnose ringworm?

Answer 37

collect plucked hair and deep skin scraping: cytology, wood’s lamp, histology

Question 38

are Dermatophytes zoonotic?

Answer 38

yes