L21 - Fungi & Medicine Flashcards
What are endoparasitic fungi?
Fungal hyphae growing out of a fully colonised nematode host. Produces sticky nematode to adhere
What are nematotrophs? What are nematodes
Parasites of nematode worms. Nematodes are trapped by specialised hyphae an d adhesive knobs. Specialised hyphae that acts like a mousse. Nematode becomes trapped in mycelium and dies
What is the infection process of insect pathogens
Spore lands on cuticle, germination, penetration of cuticle, invasion of epidermis and hypodermis, tissue invasion or proliferation of hyphal bodies or yeast like cells
Insect death
- saprotrophic growth
- dispersal by spores
What is the term for moulds and fungi that infects human? What are some examples
Mycoses
- dermatophytes (ringworm)
- commensals
- opportunistic pathogens of the lungs / wounds or traumatised tissues
- naturally living in lungs
Characteristics of dermatophytes
E.g. ringworm and athlete’s foot
- skin diseases prevalent after chronic headaches and lower back pain
- grow on dead, keratinized tissues of the skin, hair and nails
Info about dermatophytes:
- all dermatophytes are ____ fungi and are primarily ____
- reproduce by asexual spores called ___
- ____ (formed by fragmentation of hyphae) and pigmented hyphae can also spread infection
- ascomyete
- asexual
- conidia
- arthrospores
Why can’t dermatophytes invade living cells
Bc they can not grow at 37 degrees
What are the 2 structures dermatophytes hyphae can develop to aid infection
- flattened ‘hyphal fronds’ can grow in planes of weakness within a stratified substrate such as skin flakes
- hyphae can differentiate a ‘perforating organ’
Why are dermatophytes pathogens keratophillic
- they can grow on keratin rich substrates and they use it as their sole carbon source bc they make keratinases
Cánida albicans is a type of yeast. How is it opportunistic through its dimorphic nature
Type of yeast that grows harmlessly. Under appropriate conditions the fungus can change from budding yeast to hyphal growth and cause infections
Candida albicans is a major fungal pathogen of humans….
Newborn babies get thrush, pregnant women who were dentures are susceptible to thrush
What are the stages of systemic infection by Candida albicans?
Yeast to hypha - adhesion and colonization. Epithelial penetration and infiltration into tissues
Hypha to yeast - dissemination within the bloodstream
Yeast - hyphae - endothelial colonisation and penetration and infiltration into tissues Hypha
What are the cultural conditions for promoting yeast vs hyphal growth form in Candida albicans
Yeast to hyphae
- 37%
- pH7
- starvation
Hypha to yeast
- less than 30 degrees
- pH 4
- high cell density and nutrient availability
What are some characteristics of opportunistic pathogens infecting lungs
- caused by fungi that grow as saprotrophs in soil or plant/animal remains
- establish infections in the lungs from spores
- do not spread host-to-host transmission
- infections usually only to immunodeficient hosts
Opportunistic pathogens are potentially ANY fungus that:
- produce spores small enough to reach alveoli
- can grow at 37 degrees
- can withstand or evade host defences
What is the route of infection of aspergillus fumigatus route of infection
Invasion via lungs through:
1. Ciliated epithelium lining and upper regions of the respiratory tract or
2. Through alveoli
What is cryptococcus neoformans
Infects CNS causing meningitis which is fatal if untreated.
What type of fungus is cryptococcus neoformans
Basidomycete fungus (produces basidiospores)
- spends most of its life growing as a yeast
- distantly related to budding yeast
What are some pathogenicity factors of cryptococcus neoformans
- ability to grow at human body temperature
- ability to grow in presence of 5% CO2
- capsules (not easily killed by immune cells)
- melanin (protects cell from UV)
What are some main antifungal compounds used to treat human fungal diseases and their targets
- Azoles - inhibits synthesis of CM (ergosterol)
- Polyene antibiotics - associates with ergosterol in CM to form pores disrupting ion homeostasis
- Echinocandins - inhibits synthesis of cell wall
- Flucytosine - inhibits DNA and protein synthesis of fungal cells
Useful medicinal fungi
- immune boosting mushroom extract as food supplements
- super expensive fungi Chinese medicine (cordyceps)
- turkey tail trametes versicolor - immune activating and breakdown products are beneficial
- immune boosting mushroom extract as food supplements
- super expensive fungi Chinese medicine (cordyceps)
- turkey tail trametes versicolor - immune activating and breakdown products are beneficial
