Basic mycology + fungi as infectious agents Flashcards
What are eukaryotes?
Organisms whose cells have a nucleus enclosed within a nuclear envelope
What does heterotrophic mean?
Means they are consumers
What are fungi?
Eukaryotic, heterotrophic
Fungi can be saphrophytes - what does this mean?
They live off of decaying matter
Fungi can be symbionts - what does this mean?
They can live in symbiosis with other living things
Fungi can be pathogens - what does this mean?
An agent or organism that can produce disease.
An infectious agent - a germ
What are the two components of fungi?
1) Fruiting body
2) Mycelium = a network of branched, tubular filaments
What are the different forms of fungi?
1) Yeasts = single celled fungi
2) Filamentous = long strands
3) Dimorphic = yeasts or moulds
Describe fungi
- Decomposers
- Cell wall made of chitin
- Has a nucleus
- Slightly acidic in soil
- Undergoes asexual or sexual reproduction - Gain energy from dead matter
- Multicellular (apart from yeast)
How do fungi cause disease?
Fungal diseases include both the invasion of tissues by fungi and the effects on organs of fungal positions.
What are the three different ways fungi can cause disease?
1) Mycoses = invasion of tissue
2) Mycotoxicosis = ingestion of toxins
3) Fungal allergy = hypersensitivity to fungal antigens
Mycoses can be endogenous or exogenous - what do these terms mean?
Endogenous = natural commensals may become opportunistic pathogens
Exogenous = soil, decaying plant material, water or other animal
Mycoses can have different sites of infection - what are these and give examples.
Superficial = dermatomycosis
Subcutaneous = sporotricosis
Systemic = cryptococcosis
What is yeast - malasezzia pachydermatis and what can it cause?
Commensal
Causes: mild skin disease, allergies, budding on a broad base, implicated in otitis externa in dogs
What is aspergillosis?
Inhalation of fungal spores
What colour do fungi stain in a PAS stain?
Pink
What colour do fungi stain in an H&E stain?
Purple
What can sometimes be seen in an H&E stain of fungi?
Necrosis, granulomas containing yeast-like bodies
What is yeast candida albicans?
- Commensal of nasopharynx, GIT and external genitalia
- Opportunistic
- Budding on a narrow base
What is yeast Cryptococcus neoformans
- Encapsulated yeast
- Infection from environment
- Found in bird droppings
- Primary pulmonary infection (respiratory) may spread to CNS
- Sporadic
- Spherical cells, budding on a narrow base
What is filamentous fungi - saprolegniasis
- Freshwater fish
- Usually secondary infection
- Cold water
- Cotton wool like appearance on skin and gills.
What is filamentous fungi - mucormycosis
- Damages the rumen wall. If grass-fed it increases acid and there is a reduction in pH = ruminal acidosis
- Leads to fungal invasion and progresses to granulomatous rumenitis
- Also found in calves given antibiotics due to distribution in normal flora
- Can be spread via the portal vein to liver
Filamentous fungi - mucromycosis can be either… or ….
Bread mould
Sporangiospores
What does filamentous fungi cause?
- Mycotic abortion
- Guttural pouch mycosis
- Avian aspergillosis
- Pulmonary aspergillosis
- Canine nasal aspergillosis
