33 – Fungal Fundamentals Flashcards
Microbiological characteristics
- Eukaryotes (more similar to us than bacteria)
- Nucleated
- Fungal hyphae
- Cell membrane: ERGOSTEROL
- Very few encountered as pathogens
- *moulds and yeasts (morphological terms)
What is fungal hyphae?
- Cell walls composed of chitin
- *can target with anti-fungal drugs
How do you visualize them?
- KOH wet prep
- Transparency tape preparation
- India ink
- Methylene blue
Mold vs yeast
- *don’t think of them as separate branches
- Mostly morphological terms
- *some are dimorphic (yeast at 35 degree C, mould at colder temperatures)
Lifestyles
- Aerobic
- Most grow at low temperatures (20-30 degree C)
- Tolerant of high pressures and low pH
- Capable of growing a wide variety of environments
- Very good at degrading polymers
- Some found using radiation as energy
Fungi makes yummy food and drinks for us: example of Roquefort cheese
- Produces toxin: roquefortine toxin=poisonous to dogs
Fungi makes useful things: example
- Penicillin from penicillium-species of mold
Virulence factors: ‘3 presentations you can get’
- Tissue invasion: mycosis
- Toxin production: mycotoxicosis
- Hypersensitivity
Mycosis
- *tissue invasion
- What you might think of when you think ‘infection’
- Ex. guttural pouch mycosis
What are some different mycotoxicosis?
- Aflatoxicosis
- Fusariotoxicosis
- Ergotism
Aflatoxicosis: example
- Aflatoxins in feed affect poultry
Fusariotoxicosis: example
- Zearalenone is NON-toxic for poultry but causes disease in PIGS
o Reproduction in pigs
Ergotism: example
- Alkaloids produced by fungi growing on cereals
Hypersensitivity (‘virulence factor’)
- Moulds growing in damp buildings
- Exacerbation of asthma or hypersensitivity pneumonitis
- Ex. disaster clean up
Classification of fungi is a state of flux
- Classically based on morphology and sexual reproductive life cycle
- *increasingly relying on DNA sequence
What is some vocab used in taxonomy?
- Hyphae
- Mycelium
- Asexual spores
Hyphae
- Filaments which make up mycelium
Mycelium
- Mat of branching hyphae
Asexual spores
- Disseminate to other locations, germinate when conditions are FAVORABLE
o Spores in/on different structures have different morphologies
o Many different types
Clinical significance
- Relatively few are pathogenic
o Majority grow best below body temperature of endotherms - *opportunistic and not contagious
- Common cause of disease in ectotherms (plants, insects, fish, amphibians)
In mammals, what are fungi typically considered? (2)
- Commensal/host-associated
o Disease happens in states of IMMUNOSUPPRESSION - Environmentally acquired
o Disease typically follows exposure
Environmentally acquired: examples
- Many of the dimorphic fungi (ex. Blastomyces)
- Disease typically follows exposure to LARGE INOCULUM
- Understanding geographic distribution is IMPORTANT
‘nuclear winter’ from asteroid killed off plant life
- Dead plants broken down my fungi!
o Massive plume of spores - Nothing to eat for dinosaurs and needed sun to worm up
o Disease when overwhelming challenge and compromised host defenses - *perfect example of epidemiological triad
- *birds (beaks to eat seeds/nuts) and early mammals survived
What is an example of fungal disease and extinction?
- White nose syndrome in NA bats (Pseudogymnoascus destructans)
- Chytridiomycosis in amphibians
- Snake fungal disease: emerging disease in US
What are risk factors are infections in people most commonly associated with?
- Immunosuppression
- Organ transplant recipients
- SLE (lupas), vascular diseases, diabetes mellitus, alcholics
- Iatrogenic factors
- AIDS
What are some iatrogenic factors that are a risk factor in humans for infection?
- Prolonged antimicrobial, steroid or cytotoxic therapy
