Fungal and Yeast Infections

Question 1

What are the characteristics of fungi?

Answer 1

Eukaryotic
Heterotrophic saprophytes/symbionts/pathogens
Have a fruiting body (mushroom) and mycelium

Question 2

What are the different morphological forms of fungi?

Answer 2

Yeasts - single celled
Filamentous - multinucleated
Dimorphic - two phases

Question 3

Define mycoses

Answer 3

Invasion of tissues

Question 4

Define mycotoxicosis

Answer 4

Ingestion of toxins

Question 5

Define fungal allergy

Answer 5

Hypersensitivity to fungal antigens

Question 6

What are the sources of mycoses?

Answer 6

Endogenous - natural commensal that may become and opportunistic pathogen
Exogenous - soil, decaying plant material, water, other animal

Question 7

What are the different sites of mycoses?

Answer 7

Superficial - dermatomycosis
Subcutaneous - sporotrichosis
Systemic - cryptococcosis

Question 8

What are the different types of asexual fungal spores?

Answer 8

Arthrospores - fragmented hypae
Conidiospores - specialised fro spreading in large numbers
Chlamydospores - resting form
Sporangiospores - froemed inside specialised structure spores released into the environment

Question 9

How are mycoses diagnosed?

Answer 9

Microscopy
Culture
Serology
Woods Lamp

Question 10

What do you wet material with to perform microscopy of fungi?

Answer 10

KOH or paraffin oil

Question 11

What stains can you use in histopathology of fungi?

Answer 11

Fixed material - Grocott (silver stain)

Fixed material - Periodic acid Schiff (PAS)

Question 12

How do you culture fungi?

Answer 12

Sabouraud's medium or Malt extract agar
27C for filamentous for 7-10 days
37C for yeasts for 24-36 hours
Low pH
Chloramphenicol/cycloheximide to restrict bacterial growth

Question 13

Which serological tests can be used to diagnose mycoses?

Answer 13

Immunoprecipitation
CFT
ELISA

Question 14

How does a Wood’s Lamp work?

Answer 14

Emits long wave UV light which causes some dermatophytes to fluoresce green

Question 15

Which yeast typically infects the skin?

Answer 15

Malassezia pachydermatitis

Question 16

Which yeast typically affects the cutaneous/mucous membranes?

Answer 16

Candida albicans

Question 17

Which yeast can infect an animal systemically?

Answer 17

Cryptococcus neoformans

Question 18

How is Malassezia identified?

Answer 18

Buds on a broad base

Question 19

How is Candida albicans identified?

Answer 19

Buds on a narrow base

Question 20

How is Cryptococcus identified?

Answer 20

Spherical cells that bud on a narrow base

Question 21

What are the characteristics of Cryptococcus?

Answer 21

Encapsulated yeast from the environment
Pigeon droppings?
Sporadic occurrence
Primary pulmonary infection and spreads via RES to CNS

Question 22

Which filamentous fungi are pathogenic?

Answer 22

Saprolegniosis (fish)
Mucormycosis (alimentary)
Aspergillosis (mycotic abortion, gutteral pouch, avian, pulmonary, canine nasal)
Dermatophytes (ringworm)

Question 23

What is the pathogenesis of mucormycosis?

Answer 23

Bread mould or grain feed of ruminants and spreads via hepatic portal vein to the liver

Question 24

How is aspergillus identified?

Answer 24

Septate mycelium with sporing heads