fungal physiology, infections and therapeutics Flashcards
What are the features of fungi?
-cytoplasm enclosed in cell wall
-cell wall composed of complex carb polymers including chitin
How do fungi reproduce?
sexual meiosis or asexual mitosis spores
What are the two main morphological forms of fungi?
moulds and yeast
What are hyphae?
-the basic cell unit of the moulds
-an apically elongating cylinder capable of branching
what are the features of hyphae?
-at intervals, cross walls or septa strengthen the tubular wall but as these have a central pore, the cytoplasm can stream through
-the hypha is therefore acellular often with several nuceli per segment
what are mycelium?
Network of hyphae forming the body of the mould
what are the types of mycelium?
-conidia
-sporangiospores
what are yeasts?
-an alternative growth form to the hypha
how do yeasts reproduce?
budding
how can some spores produce both yeasts and hyphae?
-depends on environmental conditions
=dimorphic
what is pseudo-mycelium?
Intermediate form of growth between hyphae and yeasts, in which elongated budding cells form pseudohyphae.
what is phylum deuteromycota?
-fungi imperfecti
-if dont fit into a group
what are the features of deuteromycota?
-an artificial assemblage of fungi which only produce conidia, there being no sexual reproductive state
-most of the pathogenic species fit here
what is an example of a deuteromycota?
-aspergillus fumigatus
-causes airway disease
-conidiophore- bears a conidia
-conidia are fruiting bodies
-vesticles and phialides too
what are arthrospores?
-Conidia formed by simple fragmentation of hyphae in dermatophytes
how do fungi act as pathogens?
-mycosis (infection)
-allergy (inhaled spores)
-toxicosis
what are the ways fungi are involved in toxicosis?
-mycotoxicosis (spoiled feed)
-mycetism (ingesting poisonous fungi)
what is fungal allergy?
spores have chitin so animal allergic as doesnt recognise
what are endogenous sources of infection?
-commensal flora
-e.g. canidia in GI tract
-oral thrush
what are exogenous sources of infection?
-free living saphrophytes e.g. aspergillus in hay
-parasitic on other animal host e.g. microsporum causing ringworm
what are the three types of mycoses infections?
-superficial mycoses
-subcutaneous mycoses
-deep mycoses
what is superficial mycoses?
-epidermis
-nail/hair/claws/spines/feathers
-fungi have evolved to grow outside in colder environment which will be on outside
-land on skin and burrow roots deep down
what is an example of superficial mycoses?
-microsporum canis
-fungi glow in dark so with UV light can see ringworm lesions
what are subcutaneous mycoses?
-traumatic inoculation through skin
what are deep mycoses?
-inhaled
-deep wound
-endogenous
what are the effects of cattle ringworm?
-loss in growth rate
-lower milk yield
-scarring affects high value and stock sales
-contamination persists for years
what are the topical treatments of ringworm?
-miconaxole- shampoo
-enilconazole- wash or spray
what are the systemic treatments of ringworm?
-griseofulvin
-terbinafine and itraconazole- not licensed
what are the methods of environmental deconamination?
-restrict movements of animals
-burn bedding, collars, grooming tools
-fog spray or wash other surfaces with enilconazole, bleach or persulphate
what type of growth do deep mycoses have?
opportunistic
predisposition
what influences predisposition to fungal infection?
-immune suppression (natural or induced)
-age (young and old)
-trauma
-exposure to heavy spore loads
what are deep mycoses mould infection examples?
-aspergillosis
-mucoromycosis
-mycotic abortion
what are deep mycoses yeast infection examples?
-candidosis
-cryptococcosis
-malassezia
What Aspergillosis features?
-main sources: hay, straw
-spores 2-3um, impact on alveloar wall
-separate hyphae in tissues
aspergillosis in dogs
-bony sinuses which is difficult yo get topical agent into
-squirt it until it comes out of dogs nostrils
-difficult to diagnose and treat
-usually have the euthanise
what is bovine mycotic abortion?
-infection of placenta and foetus
-not contagious
what is the gross pathology of bovine mycotic abortion?
-thickened cotyledons, amnion and foetal skin
what is seen in cells trying to get rid of mycotic abrotion?
growth of cells
thickened skin, necrosis and lesions in amnion
what is candidosis?
-yeasts of normal gut flora
-opportunistic infections
-mucosal lesions- thrush, gut ulcers, mastitis, deep systemic
-can be deadly
how are mould infections diagnosed e.g. mycotic abortion?
-gross pathology- thickened cotyledons amnion and foetal skin
-direct microscopy- fungal hyphae in tissues and foetal stomach contents
-culture identification- only trust foetal stomach contents
what is cryptococcosis
-yeasts with capsule outside
-saprophytic in bird guano
-opportunistic (immunosuppression)
-big outbreak in mexico, live in bat poo, bird poo or caves
-can live for years and then activate and then kill
what is an important control of cryptococcosis?
dont let it dry out
what are the methods of diagnosis of fungi infections
-direct microscopy
-culture and ID
-serology
-molecular ID
what is serology?
-detect antibodies and antigens
-detect what cannot see
-like chitin
-circulating around system
