Lecture 9 - Mycology

Question 1

Describe kingdom fungi

Answer 1

mushrooms, yeast, moulds
unicell or multicel
eukaryotic
cell wall
heterotrophic - saprotrophs
non motile

Question 2

Describe the fungal eukaryotic cell

Answer 2

they have complex cell wall containing chitin
distinct nucleus + membrane bound organelles
some fungi have plasmid-like structures

Question 3

What are yeast? Describe yeast

Answer 3

fungi that grow as unicellular organisms
replicate by “budding”
ex. malasezzia, candida, saccharomyces

Question 4

What are moulds (multicell fungi)

Answer 4

Multicell fungi more complex - multiple structures, life stages, more than 1 reproduction
they have two life stages
vegetative state + repro state

Question 5

What is the vegetative state?

Answer 5

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

Question 6

What is a mycelium?

Answer 6

the mass of hyphae that form the vegetative part of a fungus

Question 7

How do you describe macroscopic mycelia?

Answer 7

when yeast or mycelium is lg enough to see on a surface, it is referred to as a colony.

Question 8

How do you describe macroscopic mycelia by the colony?

Answer 8

color (top, bottom, center, edges)
texture (powdery, granular, woolly)
size does not matter
depends on age of culture/type of media (indicate both)

Question 9

What nutrition does heterotrophs, saphrophytes and parasitics require?

Answer 9

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

Question 10

What are exoenzymes

Answer 10

-cells in hyphae release exoenzymes
-digestive enzymes release into enviro -> digest organic matter in enviro -> absorb digested materials into cell

Question 11

What are the types of fungal repro?

Answer 11

asex + sex
Asex = budding, mycelium fragmentation, producing spores
sex repro

Question 12

Describe asexual repro in fungi

Answer 12

thru mitosis
the progeny cells are identical to the parent cell

Question 13

How does budding work?

Answer 13

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

Question 14

How does mycelium fragmentationw ork

Answer 14

when pieces of hyphae break off
new section will continue to grow from tips via mitosis until new mycelium forms

Question 15

How are spores produced? what is a spore?

Answer 15

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

Question 16

What are endospores? What are they contained in?

Answer 16

sporangiospores
unicell
contained in a capsule (sporangium), which will release the endospores when disturbed

Question 17

What are conidiospores?

Answer 17

unicell or multicell spores released from tip/side of hyphae
only seen w/ microscope

Question 18

What are the two forms of conidiospores used to identify the fungus?

Answer 18

microconidia - spore made up of a single cell
macroconidia - multicell spore, the entire unit breaks off to form a new fungus

Question 19

What is the microscopic differenetiation of microsporum and trichophyton based on macroconidia from culture?

Answer 19

microsporum - macroconidia have pointy, elongated tips
Trichophyton - macroconidia have rounded tips

Question 20

How does the sexual repro of fungi work?

Answer 20

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

Question 21

Describe the 3 stages of sexual repo

Answer 21

1. plasmogamy - two haploid cells fuse and mix their cytoplasm and organelles (makes 1 lg cell, 2 nuclei)
2. Karyogamy - the 2 haploid nuclei fuse to form a diploid (2n) nucleus
3. meiosis - the chromosomes randomly sort into two different spores (n)

Question 22

Describe fungal spores, how they spread and how to deal with them

Answer 22

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

Question 23

What are mycoses? What is mycology and what can cause these diseases?

Answer 23

mycoses - fungal diseases
mycology - study of fungal diseases
can be due to infection by the fungus or exposure to fungal toxins

Question 24

Describe fungi in simple means. Where is it normal flora?

Answer 24

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

Question 25

What are the different types of mycoses?

Answer 25

1. superficial mycoses - dermatophytoses, ringworm
2. oppertunistic mycoses
3. systemic mycoses
4. mycotoxicosis

all have zoonotic potential and cause similar disease in people
very cautious working with these anims

Question 26

Describe anti-fungals?

Answer 26

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

Question 27

Describe superficial mycoses

Answer 27

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

Question 28

What are some diagnostic tests for dermatophytes?

Answer 28

wood’s lamp
tape sample of skin + hair
fungal culture - dermatophtye test medium (DTM), routine funal culture (referred test)

Question 29

How does Wood’s Lamp test

Answer 29

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

Question 30

How does the tape sample and examination work?

Answer 30

1. scotch or packing take
2. press over lesion; take skin and hair
3. in-clinic microscope examination with simple stain for spores on hairshaft

chains of spores can be on their hair shaft

Question 31

how do you prep for collecting cinical samples for culture (hair and skin scrapings)

Answer 31

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

Question 32

how do you collect cinical samples for culture (hair)

Answer 32

1. hair should be pulled/plucked out (not cut)
2. if wood’s lamp pos, take flurorescent hairs
3. if there are broken hairs, take broken hairs

Question 33

how do you collect cinical samples for culture (skin scrapings)

Answer 33

1. collect any crusts
2. 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)

Question 34

How do you collect spores with a toothbrush?

Answer 34

1. use new toothbrush (medium to hard bristles)
2. brush all over hairs to collect spores
3. submit whole toothbrush

Question 35

How do you transport clinical samples?

Answer 35

1. 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
2. room temp

Question 36

how do you culture dermatophytes?

Answer 36

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

Question 37

How do you inoculate DTM?

Answer 37

1. place hair + skin scrapings onto the surface of the media or press bristle of toothbrush onto surface of media
2. press gently to adhere to surface of media
3. must seal container so media does not dry out
4. leave at room temp, dark
5. takes up to 3 wks

Question 38

What happens with a positive DTM test?

Answer 38

-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

Question 39

How do you preven the spread of ringworm?

Answer 39

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

Question 40

What are opportunistic mycoses?

Answer 40

req vry lrg inoculum/ immunocomp host
Ex. aspergillosis

Question 41

What is aspergillosis

Answer 41

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

Question 42

What is candida

Answer 42

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

Question 43

Malessezia

Answer 43

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

Question 44

What are systemic mycoses?

Answer 44

infections of int tissues/organs
transmission by inhalation of spores
severe, difficult to treat, life-threatening,

blastomycosis common in SK

Question 45

What is blastomycosis?

Answer 45

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

Question 46

What is mycotoxicosis?

Answer 46

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

Question 47

What is moldy sweet clover?

Answer 47

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

Question 48

What is ergot?

Answer 48

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