Introduction to Fungi and Superficial Mycoses Flashcards
how do fungi reproduce?
sexual and asexual
are molds multicellular or unicellular?
multicellular
what does it mean that a fungus is monomorphic?
one form in environment and host
what does it mean that a fungus is dimorphic?
two forms
triggered by temperature, CO2
how long does fungus culture/growth in culture take?
days to weeks
what are the five Ds of fungal diseases?
debilitating
destructive
difficult to diagnose
difficult to treat
do not have effective vaccines
fungal diseases are ________________________, but not always
often opportunistic
what are the host defenses against fungal infections?
intact skin and mucosal surfaces
low pH
antimicrobials
normal flora
mucus
what does Dermatophytosis (ringworm) infect?
keratinized tissues: epidermis, hair, feather, claws
what are the virulence factors of Dermatophytosis (ringworm)?
enzymes: keratinases digest keratin in skin, hair, nails, horn
are Dermatophytes zoonotic?
yes
what are the components of fungi cell walls?
chitin
ergosterol
beta-glucagon
cellulose
what are the two morphologic forms of fungi?
molds
yeast
how do yeasts reproduce sexually?
conjugation
rare
what are hyphae?
mycelia
branching filaments: septate branches
how do fungal cell walls stain with periodic acid schiff’s stain?
pink
how do fungi stain with grocott’s methenamine silver stain?
black
what are some monomorphic fungi?
Aspergillus spp: mold
Malassezia spp: yeast
what is one dimorphic fungus?
Coccidioides immitis
what types of diseases can dimorphic fungi cause?
deadly
what is a polymorphic fungus?
Candida albicans
what are the steps of germination for a mold?
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)
how are patients usually exposed to fungi?
environmental
what host factors increase disease risk and severity?
prolonged antibiotics
immune compromise
very young/old
persistent moisture
co-morbidities
what pathogen factors increase disease risk and severity?
dose
virulence factors
ability to invade or evade
what is a fungi that infects nails and produces keratinocytes?
Onchomycosis
what virulence factors help fungi survive inside the host?
capsule and cell wall: resist phagocytosis and low pH
enzymes: catalases, proteases
iron binding proteins
are dermatophytoses primary pathogens or opportunistic?
primary pathogens
what is the most common cause of animal candidiasis?
Candida albicans
how do Candida spp lead to systemic spread?
vascular invasion by hyphae or pseudohyphae
are Malassezia spp monomorphic, dimorphic, or polymorphic?
monomorphic
what diseases do Malassezia spp cause?
otitis externa
dermatitis
what opportunistic conditions lead to Malassezia spp causing disease?
moist skin
ear canal
what are some associated conditions of Malassezia spp?
allergy
seborrheic dermatitis
bacterial dermatitis
what are the virulence factors of Malassezia spp?
lipases
zymogens
proteases
is ringworm a commensal?
no
how can you diagnose ringworm?
collect plucked hair and deep skin scraping: cytology, wood’s lamp, histology
are Dermatophytes zoonotic?
yes
