Fungi - Morphology and Diagnostic Flashcards
What are fungi?
Eukaryotic organisms that are encased within a rigid cell wall.
What is the cell wall of fungi made up of?
Chitin
Flucan
Mannon
Glycoproteins
Various combinations of these structural components.
Where are fungi found?
Ubiquitous in the enviroment.
Some species of yeast are commensals in humans. (candida in GI tract)
Do fungi cause disease?
Rarely, mostly in immunocompromised patients.
Exception to this is dermatophytes in most dimorphic fungi.
How are fungal diseases commonly classified?
By causative organism
By clinical presentations
What type of organism is yeast?
Unicellular, round/oval shaped fungi
How do yeast reproduce?
Asexually.via budding.
Do yeast form hyphae?
No they form pseudohyphae which are elongated cells that can be confused with true hyphae from mould.
Do yeast form spores?
No
How large are yeasts?
3 - 4 micrometers but can be up to 40 micrometers
What do yeast look like macroscopically?
White and thready
What yeast are clinically significant?
Candida species
Cryptococci (cryptococcus neoformans and cryptococcus gatti)
Other rare fungal diseases also exist.
What are mould?
Multicellular fungi
Do moulds form hyphae?
Yes
What are hyphae?
Chain of multinucleate, tubular, filament-like cells
How do hyphae divide?
Each hypha has a rigid cell wall and elongates via mitosis. May be septated or aseptated
What is a tangled mass of hyphae visible to the naked eye called?
Mycelium
What are the types of mycelium?
Vegetative mycelium (extend into culture media and responsible for absorbing water and nutrients)
Aerial mycelium (extend into the air and is required for reproductions
How do fungi reproduce?
Both sexually and asexually.
They use spores or conidia for asexual reproduction.
How are conidia formed?
From a group of specialised cells called conidiogenous cells.
What are annellides?
Annellides (produces conidia by series of short percurrent proliferations and annellides slowly increase in length)
What is a conidiophore?
Specialized hyphal segment responsible for supporting a conidia bearing head.
What do conidiophores branch into?
Further branch into segments called metulae
What are phalides?
Phalides (produce conidia without increasing in length)
What structures vary between genus and species?
Spore morphology that varies includes:
Conidia shapes
Size of conidia
Arrangement of conidia
Septation (if present)
Colour
Texture
Locations of and shapes of conidiogenous cells (phalides or annellides, shape)
What is fungal morphology used for?
It is used to identify different fungal infections
What is hyphomycosis?
A disease caused by fungus in the class hyphomycetes
What are the classes of hyphomycosis?
Hyaline hyphomycosis (Hyalophyphomycosis)
Demetiaceous Hyphomycosis
What is used for classification of hyphomycosis?
Colour of the mycelium and conidia
What is the most common cause of hyaline hyphomycosis mould infections?
Aspergillus (most common)
Penicillium, fusarium and others may also cause diseases
What does hyphae morphology look like in aspergillus?
Septated hyphae that branch 45 degrees.
Conidiophore is 90 degrees from hyphae
Metulae and phialides grow from the vesicles. Phialides produce conidia.
What does hyphae morphology look like in macroconidia (fusarium)?
Macroconidia
What kind of infection do macroconidia (fusarium) cause?
In normal immune system (keratitis and contact lens associated disease)
In immunocompromised people (disseminated blood stream infection and invasive lung and skin infection)
What kind of infections does scedosporium prolificans cause?
in immunosuppressed hosts causes lung infections, blood stream infections, and rarely can cause keratitis
What do conidial look like in scedosporium prolificans?
Clustered and tear shaped.
Flask-shaped phalides
What kind of infections does dermaticaeous hyphomycosis cause?
Opportunistic infections and cutaneous infections in immunocompromised people.
How diverse is dermaticaeous hyphomycosis?
Widely heterogenous
What group of people does mucomycosis most commonly infect?
Immunosuppressed people primarily people with haematological malignancies