Mycology Flashcards
What are Eukaryotes?
- organisms whose cells have a nucleus enclosed within a nuclear envelope
What does heterotrophic mean?
- means they are consumers
What can fungi be?
- eukaryotic
- heterotrophic
Fungi can be saprophytes - what does this mean?
- they live off dead or decaying matter
Fungi can be symbionts - what does this mean?
- they can live in symbiosis with another living thing
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?
- fruiting body
- mycelium - is a network of branched, tubular filaments
What are the different forms of fungi?
- yeasts - single celled fungi
- filamentous = long strands
- dimorphic = yeasts or moulds
Describe bacteria:
- producers and decomposers
- cell wall made of peptidoglycan
- no nucleus
- neutral pH
- round, spiral or rod shaped
- asexual reproduction
- energy from sugars and proteins
- unicellular
Describe fungi:
- decomposers
- cell wall made of chitin
- has a nucleus
- slightly acidic soil
- thread like structures - various shapes
- sexual or asexual reproduction
- energy from dead matter
- multicellular (apart from yeast)
How do fungi cause disease?
- fungal disease include both the invasion of tissues by fungi and the effects on organs of fungal poisons
What are the three different ways fungi can cause disease?
- mycoses = invasion of tissue
- mycotoxicosis = ingestion of toxins
- 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 = sporotrichosis
- Systemic = cryptococcosis
What is yeast - Malasezzia pachydermatis and what can it cause?
- commensal
- mild skin disease (superficial)
- 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 grain fed it increased 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 - Mucormycosis can be either … or …?
- bread mould
- sporangiospores
What does filamentous fungi cause?
- mycotic abortion
- guttural pouch mycosis
- avian aspergillosis
- pulmonary aspergillosis
- canine nasal aspergillosis
What structural feature does FF aspergillosis have?
- sporing heads
- separate mycelium
What is Filamentous fungi dermatophytes?
- the fungi that cause ringworm - dermatomycosis
- affects skin in most species
- 3 genera
What the 3 types if dermatophytes?
- Microsporum sp
- Trichophyton sp
- Epidermophyton sp
What two types types if fungi are associated with dermatophytes?
- Keratinophilic fungi = breakdown hair and colonise keratinous substrates degrading them into components of low molecular weight
- Contagious fungi
What are the dermatomycosis - epidemiological groups?
- anthropophilic
- zoophilic
- geophilic
What hosts do Anthropophilic prefer?
- preferring human hosts over other animal
What hosts preferences do zoophilic have?
- preference to animal host
= all zoonotic
What host preference do geophilic have?
- preferring soil host
What is Dermatomycosis clinical appearance?
- crusty grey lesions on the head and neck
- seen in calves, dogs, horses, cats, poultry
How do a wet preparation for microscopy?
- scrape or smear and add (KOH) potassium hydroxide or paraffin oil
What two mediums can be used for cultures?
- sabouraud’s medium
- malt extract agar
How long do you leave filamentous to culture for and at what temperature?
- 27 degrees Celsius
- for 7-10 days
How long do you leave yeasts to culture for and at what temperature?
- 37 degrees Celsius
- for 24-36hrs
What pH do you culture at?
- low pH
What antibiotics do we use on cultures?
- chloramphenicol
- cycloheximide
What is serology used for?
- detecting the antibody in animal serum from a clotted blood sample
What tests can be used in serology?
- ELISA
- CFT
- Immunoprecipitation
What is CFT used for?
- CFT complement fixation test. – Used for histoplasmosis, blastomycosis, aspergillosis and coocidioidomycosis.
- Antibodies are present in the serum, when mixed with the corresponding antigens, they will bind. Then use an assay system
- if antibody is present there will be no fungi as its all bound
- if antibody in blood not present there will be fungi
How can be diagnose dermatomycosis?
- history and clinical signs
- use woods lamp
- microscopy
- culture
- sample - pluck hair or scrap
How does a dermatomycosis woods lamp work?
- uses long wave UV light which reflects of skin
- if present there will be an apple green fluorescence on hair and skin
How do you culture dermatomycosis?
- sabourauds agar
- use antibiotics to prevent bacteria invasion
- different strains look different
- usually at 27’C
What does PAS strand for?
- periodic acid-schiff stain
How does dermatomycosis stain?
- PAS stain on fixed tissue
- fungi will stain purple/red
What animals does Dermatomycosis affect?
- dogs
- cats
- and others
What is the Dermatomycosis infection associated with?
- young animals
- grooming equipment
- minor trauma
- mixing with other animals
- mixing with wild animals
How can Dermatomycosis be controlled?
- disinfectants
- shampoos
- avoid mixing
How can Dermatomycosis be treated?
- Griseofulvin - oral
- Azole antifungals - oral or topical
How does ringworm develop and spread (pathogenesis)?
- Arthrospores germinate
- Infective hyphae grow into the skin and down the hair follicle
- Hyphae grow downwards & penetrate within hair shaft
- Arthrospores form around the now brittle hair shaft as the hyphae age
- The hair breaks and falls away – infecting the environment
- Hyphae will not penetrate living tissue
In Dermatomycosis what may a secondary bacterial infection cause?
- may cause permanent damage to the follicle and dermis
