Lecture 9 - Mycology Flashcards
Describe kingdom fungi
mushrooms, yeast, moulds
unicell or multicel
eukaryotic
cell wall
heterotrophic - saprotrophs
non motile
Describe the fungal eukaryotic cell
they have complex cell wall containing chitin
distinct nucleus + membrane bound organelles
some fungi have plasmid-like structures
What are yeast? Describe yeast
fungi that grow as unicellular organisms
replicate by “budding”
ex. malasezzia, candida, saccharomyces
What are moulds (multicell fungi)
Multicell fungi more complex - multiple structures, life stages, more than 1 reproduction
they have two life stages
vegetative state + repro state
What is the vegetative state?
Vegetative fungal cells are arranged end-on-end to form long slender strands called hyphae - can also branch
Hyphae can spread, cells at tips mitosis
the end of each cell made up of “endwall” and two end walls form a septum
septum contains sm holes for cytoplasmic material exchange
not all phyphae are septate
makes a mycelium, forms on surfaces, underground, liquid
What is a mycelium?
the mass of hyphae that form the vegetative part of a fungus
How do you describe macroscopic mycelia?
when yeast or mycelium is lg enough to see on a surface, it is referred to as a colony.
How do you describe macroscopic mycelia by the colony?
color (top, bottom, center, edges)
texture (powdery, granular, woolly)
size does not matter
depends on age of culture/type of media (indicate both)
What nutrition does heterotrophs, saphrophytes and parasitics require?
Hetertrophs - all gunfi req nutr prod to them in form of complex organic molecules
Saphrophytes - almost all gunfi aquire nutr from dead or decaying organic matter
parasitic - some fungi infect plants or anims for nutr
What are exoenzymes
-cells in hyphae release exoenzymes
-digestive enzymes release into enviro -> digest organic matter in enviro -> absorb digested materials into cell
What are the types of fungal repro?
asex + sex
Asex = budding, mycelium fragmentation, producing spores
sex repro
Describe asexual repro in fungi
thru mitosis
the progeny cells are identical to the parent cell
How does budding work?
Asex in yeast
bulge forms on side of cell, cell contents replicate fill new bud, chromosomes mitosis, new copy of genome also moves into bud
single bud or chains of buds
How does mycelium fragmentationw ork
when pieces of hyphae break off
new section will continue to grow from tips via mitosis until new mycelium forms
How are spores produced? what is a spore?
Spore: repo particle, usually a single cell, released by a fungus, that may germinate into another
spore is identical to parent
when fungus is disturbed, spores release from parent
diff types of spores help identify fungus
What are endospores? What are they contained in?
sporangiospores
unicell
contained in a capsule (sporangium), which will release the endospores when disturbed
What are conidiospores?
unicell or multicell spores released from tip/side of hyphae
only seen w/ microscope
What are the two forms of conidiospores used to identify the fungus?
microconidia - spore made up of a single cell
macroconidia - multicell spore, the entire unit breaks off to form a new fungus
What is the microscopic differenetiation of microsporum and trichophyton based on macroconidia from culture?
microsporum - macroconidia have pointy, elongated tips
Trichophyton - macroconidia have rounded tips
How does the sexual repro of fungi work?
Thru meiosis
allows genetic variation’triggered by changes in enviro conditions
req spore 1 and 2
spores an be from same or diff mycelium
3 staged, plasmogamy, karyogamy, meiosis
Describe the 3 stages of sexual repo
- plasmogamy - two haploid cells fuse and mix their cytoplasm and organelles (makes 1 lg cell, 2 nuclei)
- Karyogamy - the 2 haploid nuclei fuse to form a diploid (2n) nucleus
- meiosis - the chromosomes randomly sort into two different spores (n)
Describe fungal spores, how they spread and how to deal with them
spread easy in wind/air
very difficult to destroy - resistant to all detergents, most chemical disinfectant, drying, heart, extreme cold
standards of sterilization are designed to be able to destroy fungal spores and bacterial endospores
What are mycoses? What is mycology and what can cause these diseases?
mycoses - fungal diseases
mycology - study of fungal diseases
can be due to infection by the fungus or exposure to fungal toxins
Describe fungi in simple means. Where is it normal flora?
ubiquitous in the enviro
most saprophytic, non-pathogenic
many pathogenic species are transmitted via fomites - dog inhales spores or hyphae while digging in soil
part of normal flora (eyes, skin, gi tract, urogenital tract
What are the different types of mycoses?
- superficial mycoses - dermatophytoses, ringworm
- oppertunistic mycoses
- systemic mycoses
- mycotoxicosis
all have zoonotic potential and cause similar disease in people
very cautious working with these anims
Describe anti-fungals?
drugs used to treat fungal infection
more side-effect bc fungi are eukaryotic cells - drugs also act on anims cells
antifungals only work on replicating cells - cannot treat spores
Describe superficial mycoses
commonly seen
infection of the epidermis, hair, nails,
rarely spread to underlying tissues
secrete extracellular enzymes that break down keratin
in cattle, eq, feel, k9, humans
fungal agents - microsporum, trichophyton
What are some diagnostic tests for dermatophytes?
wood’s lamp
tape sample of skin + hair
fungal culture - dermatophtye test medium (DTM), routine funal culture (referred test)
How does Wood’s Lamp test
approve 50% of cases of microsporum canis will fluroresce under the long-wave UV light
never a definitive test, never the only test
Lots of false negs - 50% of micosporum do not fluoresce, trichophyton never fluoresces
Lots of false pos - purulent discharge, certain dyes, conditions fluoresce
How does the tape sample and examination work?
- scotch or packing take
- press over lesion; take skin and hair
- in-clinic microscope examination with simple stain for spores on hairshaft
chains of spores can be on their hair shaft
how do you prep for collecting cinical samples for culture (hair and skin scrapings)
Prep - wear gloves, wipe area w/ 70% alcohol swap to remove surface bact contam and medication, ALWAYS take samples from OUTER MARGINS OF LESION where fungus is actively growing
how do you collect cinical samples for culture (hair)
- hair should be pulled/plucked out (not cut)
- if wood’s lamp pos, take flurorescent hairs
- if there are broken hairs, take broken hairs
how do you collect cinical samples for culture (skin scrapings)
- collect any crusts
- can also perform superficial skin scraping of the affected area - from edge of lesion -from red border if present, use edge of blunder scalpel blade (no mineral oil)
How do you collect spores with a toothbrush?
- use new toothbrush (medium to hard bristles)
- brush all over hairs to collect spores
- submit whole toothbrush
How do you transport clinical samples?
- place in dry sterile contained such as a sealed envelope (tape shut, DO NOT LICK) or sterile container
no plastic bags or moisture will cause any bact contam to grow preferentially - room temp
how do you culture dermatophytes?
2 methods
1. routine culture on supportive media - can culture all types of fungi
2. DTM - specific media designed to grow trichophyton and microsporum, prods easy to recognize colonies, contains a dye that turns red/pink int he presence of exoenzyme secreted by dermatophytes
How do you inoculate DTM?
- place hair + skin scrapings onto the surface of the media or press bristle of toothbrush onto surface of media
- press gently to adhere to surface of media
- must seal container so media does not dry out
- leave at room temp, dark
- takes up to 3 wks
What happens with a positive DTM test?
-media turns red AND colonies are white and fluffy
- minimum 9 days for pos culture on reg DTM
- Minimum 2 days for pos culture on rapid DTM (lots of false pos)
- neg cultures must wait 3 wks
How do you preven the spread of ringworm?
ZOONITC
wear gloves + lab coat/gown
wipe exam tables w/ damp cloth to prevent dispersal of spores
clean all in-contact instruments/equipment - use disinfecting agent w/ fungicide claims
vacuum repeatedly, do not sweep
follow w/ mop with disinfectant
What are opportunistic mycoses?
req vry lrg inoculum/ immunocomp host
Ex. aspergillosis
What is aspergillosis
aspergillus fungi
common in enviro, not normalf lora
oppertunistic infection - not very pathogenic
all species suspectible
commonly infects respirator - lungs, nasal, guttal puch, causes abortions/mastitis
What is candida
yeast
normal flora in upper resp tract, GI, genital mucosa
opportunistic infection if immunocomp or if antibiotics remove bact competing for same space
common infection spots in dogs, oral cavity, MM such as UGT
Soft white growth over surface, also cause severe system infections
Malessezia
Yeast
normal flora of skin/eats
opporsunistic infection
overgrowth if moist/hot or antibiotic therapy removes bact
common infections in ears, skin, feet
bowling pin shape
What are systemic mycoses?
infections of int tissues/organs
transmission by inhalation of spores
severe, difficult to treat, life-threatening,
blastomycosis common in SK
What is blastomycosis?
infection caused by blastomyces dermatitidis
fungus is endemic in N. america, great lakes, prevalent in regina
found in both year/mycelium forms
mycelium and spores loc in ground in decaying vegetation. dogs inhale when digging, spread systemically, always found n yeast form in clin samples
primary pathogen, zoonotic, common cause is pulmon infection
What is mycotoxicosis?
fungal toxicosis
funal can spread toxins which either remain in cell or secrete to enviro (contam of feed with mould, mushroom/compost ingestion)
most are resistant to heat/chemicals
severe dz: gi effects, neurotoxins, cardiotoxins, hallucinogens, carcinogens
What is moldy sweet clover?
certain legume (sweet clover) prod coumarin
coumarin converted by mould to dicoumarin
if ingested by cattle - binds vita K, cannot use vita K in clotting process, bleeding out risk
What is ergot?
dz caused by claviceps purpurea
mould infects rye, barely, wheat, oats, grasses
mould prod toxins cause dz when ingested
vasoconstriction most common - tissue necrosis
neurological dz
abortion
