Mycology

Question 1

3 morphological groups of fungi?

Answer 1

• yeasts (single celled)
• filamentous funghu
• dimorphous funghi (yeasts/filamentous)

Question 2

How do funghi reproduce?

Answer 2

• vegetative growth
• spore production
  > spores are stable if dry but killed by disinfectants and boiling

Question 3

What are arthrospores?

Answer 3

• disartculation of septate hyphae into separate cells
• vegetative spores
• frequently produced by dermatophytes in skin and hair

Question 4

What are conidiospores?

Answer 4

• asexual spores
• formed externally by abstriction of a conidiophore/directly from mycelium/prudced within specialised fructification
• may be uni or multicellular
• IN CULTURE ONLY dermatophytes produce 2 types conidia (no. cells and size= micro/macroconidia)
  > in hairy skin dermatophytes exist only as hyphae or arthroconidia

Question 5

What are sexual spores useful for?

Answer 5

• identifying class of fungus (4 classes)

Question 6

What 3 ways may fungus cause disease?

Answer 6

• Mycoses (growing and invading tissues)
• Mycotoxicoses (producing toxigenic substances)
• Allergy (produce substances that sensitise host)

Question 7

What funghi are capable of causing damage via mycoses?

Answer 7

> 1* eg. 
- deramtophytes
- histoplasma
- coccidiodes
> 2* opportunistic eg. 
- candida 
- aspergillus
- zygomycetes

Question 8

How are mycotic lesions further subdivided?

Answer 8

• superficial/cutaneous (eg. ringworm, pathogenesis = bacterial/viral disease with short incubation period, sudden onset and spontaneous healing)
• subcutaneous (eg. sporotrichosis) and systemic (internal organs affected eg. aspergillosis) resemble aberrant bacterial disease eg. TB with protracted incubation period, insidious onset of symptoms, may be fatal
  > endogenous or exogenous

Question 9

Are fungal infections contagious?

Answer 9

> Not normally - parasitic state is of littel significance to fungal lifecycle
- each case usually is picked up individually from environment
conidiospores may spread through the air

Question 10

How can mycoses cause damage in the host?

Answer 10

• penetration of tissues
• pressure on adjacnet tissues
• thrombi (zygomycetes predilection for BVs)

Question 11

Which yeasts can cause mycosis?

Answer 11

> cryptococcus neoformans

• spherical yeast
• polysacharide capsule
• main source = pigeon droppings full of creatinine
• infects via resp or penetration
• acute/sub/chronic infection
• exogenous
• no clearly defined clinical pattern
• resp/CNS/systemic disease (can cause meningitis)
• cattle: mastitis
• horses: myxoma like lesions
• dogs and cats: oral/pulmonary/cutaneous lesions
• cats: resp tract + proliferative nasal lesions esp. tip of nose

Question 12

Which pathogen causes thrush? What type of fungus is this? Common in animals?

Answer 12

Candida albicans
- endogenous mainly
- other candida ay be exogenous
> rare in animals cf. humans

Question 13

What type of fungus is malassezia?

Answer 13

• lipophilic
• normal skin and mucosa commensal
• opportunistic pathogen of dogs
  > otitis externa
  > dermatitis