Fungi Flashcards
Problem of fungi being euk
Fewer antifungal reagents
Classification
Traditionally on absence or presence and type of sexual spore
Ascomycota
Septate hyphae
Eg candida, aspergillus
Basidiomycota
Septate hyphae
Eg cryptococcus
Zygomycota
Non-septate hyphae
Eg mucor, mortierella
Chytridiomycota
Non-septate hyphae
Eg algal parasites
Fungi and discrim of pathogenic fungi
Usually aerobes with optimum growth of 20-30 degrees. An indication of a pathogenic fungi would be the ability to grow at 37 degrees
Divided into yeasts moulds and dimorphs
Yeasts
Unicellular but larger than bact
Oval/round G+ve
Repro by budding, can form spores
May form from a projection/germ tube from parent
Mould
Filamentous
Grow parrallel and close to surface
Branches mat to form an interconnected or vegetative mycelium which can be cms long
Hyphae
Septate or nonseptate
Septation often incomplete so have small central pore so organelles or nuclei can pass
Under certain conditions perpendicular hyphae produced. At tips of these conidiophores are formed cont conidia (asex spores)
Dimorphism
Most pathogenic fungi
Transition between 2 forms dep on enviro:
Yeast in tissue/37 degrees
Mould outside host/lower temp
CW struct
Cont chitin mannopto and beta glucans
Also have a plasmolemma (CM) cont sterol: ergosterol
Condiophore
Specialised conidia prod hyphae
Conidium
Asex spore form at tip and sides of hyphae
Arthrospores
Asex spores form within hyphae
Chlamydospores
Asex res thick walled spores
Sporangium
Closed struct cont sporangiospores
Blastoconidia
Buds that arise from yeast
Types of fungal dis
Contag cut dis: ringworm caused by dermatophytes
Cut or muc infections
Systemic or tissue infections
Sensitization: allergic react to fungal product
Mycotoxic dis: ingest preformed toxic products
Ringworm transfer
From one animal to another by conidiospore infection usually
Can be zoonotic
Some species show host spec others dont
Basic ringworm tissue destruct
Fungi can hydrolyse keratin for growth and gen restricted to living in cornified non living keratin layer and appendages
Ring worm caused by
Dermatophytes: mainly microsporum and trichophyton
Ringworm host response
Causes lesions as much as fungi virulence factors
Causes spread of dermatophytes away from infectious focus toward normal hide/skin
Gives circular ring appearance
Ring worm pathogenesis
Minor trauma key to infect intro
Conidia or hyphae fragments introduces to stratum corneum germinate and prolif
Hyphae
Invade wall of hair follicles and eventually emerge into follicular canal
Penetrate hair cortex
Hyphal prolif and conidia form in peripilat space and cortex
Keratinase collagenase and elastase role in ringworm
Contrib to spread and damage to hairs
Ringworm diagnosis
Microscopy or culture
M canis most difficult and req culture to diagnose
Many (not canis) can be diagnosed by fluorescence under UV light
Hair plucking or scraping of ringworm preparation
Made using DMSO and KOH to digest pro debris and give clearer image then scrapings plated onto selective agar
Candida albicans
Grows as budding yeast prod pseudohyphae in animal tissue
Present in small no on skin and muc surf
Candida predisp factors to infection
Depression of normal flora
Nutrition, imm or management factors
Candida thrush sysmptoms
Prod localised pyogenic lesions in mouth intestine or genital tract
Infect on muc mem charct by white grey pseudomembranous inflam patches
Candida virulence factors
Prod EC toxin and enz eg neuraminidase and proteases
Candida other infections to thrush
Crop mycosis young chickens and turkeys Mastitis in cows Enteritis and mycotic stomatitis in young cats and dogs Genital infection in horses and primates Systemic infections rare
Candida diagnosis
Suggestive lesion presence and direct microscopy
Soft creamy colonies on Sabouraud agar after 24-48hr and demo of large chlamydospores
Cyrptococcus neoformans
Budding yeast of variable size
Not produce pseudohyphae
Dogs cats foxes horses ferrets guinea pigs and some birds potentially humans
Have large capsule and prod shiny slimy colonies of Sabouraud agar initially white then dev a yellow brown tinge
Cyrptococcus neoformans infection route and cause
Inhalation with 1o infect in resp syst, pharynx and paranasal sinuses
Can dissem to CNS resulting in yeast like cells detected in CSF or in 1p infection pus
Malassezia pachydermatis
Commensal on oily areas of dogs skin and ears
Usually isolated alone or with certain bact as cause of canine otitis externa
Yeast recog from lesions due to russian doll appearance
Can also cause chronic dermatitis
Systemic and tissue mycoses causes and found
Geograph isolated
1o pathogens
Non in UK
All dimorphic
Dimorphic fungi appearance
Grow as mould with hyphae externally as saprophytes. Appears more stable form
Yeast like internally
Dimorphic fungi targets
Many target lungs but some have more gen spread
Some are highly contagious to humans
Aspergillus pathogenic species
Fumigatus
Niger
Nidulans
Aspergillus info and virulence factors
Ubiquitous soil saprophytes
Produce many EC toxins and enz causing virulence incl haemolysins and proteases
Aspergillus diseases
Nasal aspergillosis
In dogs
With persistant turbinate or sinus infect
Fungal hyphae seen in turbinate surf during rhiniscopy
Can dissem causing widespread granulomas
Aspergillus diseases in cows
Mastitis
Mycotic pneumonia
Mycotic abortion: 0.5% of abortion, other cause mortierella wolfii
Aspergillus diseases guttural pouch mycosis
In horses
Inhalation of spores can result in mycelia germ and cover large muc areas
Infection can involve arteries and nerves and can cause horse abortion
Aspergillus diseases
Brooder pneumonia
Avian
Diffuse airway infection
Hyphae often visualised by microscopy of assoc lesions
Most prod granulomatous react around nasal area or at wound site
Inhalation sensitivity and best doc eg
Many airborne can be involved in hypersensitivity react
Best documented is actinomycete - micropolyspora faeni cause of farmers lung in hum, extrinsic allergic alveolitis if cattle and maybe COPD of horses
Mycotoxosis and cause
Acute or chronic intoxication by ingest tox released by fungi on crops or in feed stores
Toxins are metabolic by products prod under spec circumstances
Outbreaks often seasonal and sporadic assoc with batches or certain pastures
Mycotoxosis diagnosis and severity dep
On quantity and type of toxin and re exposure prev
Diagnosis difficult as req demo of tox in food, tissue or excretion
Ergotism
Ingestion of infected grasses and cereals Usually caused by claviceps purpurea Release ergot alkaloids Gangrenous (chronic) Convulsive (acute) Caused by ergotamine and ergometrine
Aflatoxosis
Aflatoxins prod by aspergillus flavis and parasticus growing on stored crops
Effects pigs cattle poultry and trout
Can have long term carcinogenic effects
