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Microbiology > Unit 9 > Flashcards

Unit 9 Flashcards

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1
Q

Describe the kingdom of Fungi

A

Includes; mushrooms, yeast, and moulds

Can be unicellular or multicellular

Eukaryotic (has a nucleus and membrane bound organelles)

Has a cell wall

Heterotrophic -saprotrophs (feed on dead/decaying organic material)

Non motile

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2
Q

Describe the fungal eukaryotic cell

A

Complex cell wall contains Chitin (a carbohydrate found in insect exoskeletons)

Distinct nucleus and membrane bound organelles

Some have plasmid-like structures

Requires 400x-1000x magnification to see individual cells (larger than bacteria)

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3
Q

Yeast are fungi that grow as

A

Unicellular organisms

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4
Q

How do yeast replicate

A

Budding

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5
Q

Give examples of yeasts

A

Malasezzia (skin/ear infections)
candida
saccharomyces (bread/beer)

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6
Q

Describe moulds

A

Multicellular fungi (most fungi)

Complex; have multiple structures, multiple life stages, and more than one type of reproduction

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7
Q

What are the two life stages of moulds

A

Vegetative state

Reproductive state

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8
Q

Describe the vegetative state of moulds

A

Vegetative fungal cells are arranged end to end to form long strands (can branch) called Hyphae

Hyphae spread at the tips by mitosis

The end of each cell is an “end wall” and two end walls form a septum, the septum contains holes that allow for exchange of cytoplasmic materials between adjacent cells (not all hyphae are septate)

As hyphae continue to divide/branch, a mycelium forms (mass of hyphae that form the vegetative part of a fungus)

Can form on surfaces, underground or in water

Have a fuzzy surface

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9
Q

True or false

Hyphae are the individual vegetative cells and mycelium are the whole vegetative part of the fungus made of hyphae

A

True

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10
Q

When a yeast or mycelium is large enough to see on a surface it is called a

A

Colony

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11
Q

How do you describe macroscopic mycelia

A

Color (can have different colors throughout)

Texture

Depends on age of culture and type of media (always indicate these)
Size does NOT matter

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12
Q

How are fungi heterotrophs

A

All fungi require nutrition provided to them in the form of complex organic molecules

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13
Q

How are fungi saprophytes

A

Almost all fungi acquire nutrients from dead or decaying matter

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14
Q

How are fungi parasitic

A

Some fungi can infect plants or animal cells to obtain nutrition

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15
Q

Describe a fungi’s exoenzymes

A

Cells in hyphae release exoenzymes

These digestive enzymes are released into the environment to digest organic matter around them, the nutrients released are absorbed into the cell

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16
Q

True or false

Fungi have both asexual and sexual reproduction methods

A

True

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17
Q

What are the 3 asexual methods of reproduction in fungi

A

Budding (yeast)
Mycelium fragmentation
Producing spores

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18
Q

Asexual reproduction is achieved by ___ and results in progeny cells ___ to parents cells

A

Mitosis

Identical to parent cells

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19
Q

Describe budding

A

Asexual reproduction in yeast

Bulge forms on the side of the cell, cell contents replicate and fills the new bud, chromosomes undergo mitosis, a new copy of the genome moves into the bud

A single bud or chain of buds is formed depending on the species

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20
Q

Describe mycelium fragmentation

A

Pieces of hyphae break off and a new section will continue to grow from the tips via mitosis until a new mycelium forms

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21
Q

Describe asexual reproductive via producing spores

A

Spore: a reproductive particle, usually a single cell, released by a fungus, that may germinate into another hyphae and eventually a new mycelium (must be done in good conditions)

The spore is identical to the parent cell

Spores are released when the fungus is disturbed -these are carried to other locations to allow spread

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22
Q

True or false

Producing spores is the most common method of asexual reproduction in fungi

A

True

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23
Q

Different types of spores can be used to help

A

Identify different fungi

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24
Q

What are endospores

(AKA sporangiospores)

A

Spores are unicellular

Contained in a capsule (sporangium) which will release the endospores when disturbed

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25
What are conidiospores
Unicellular or multicellular spores that are released directly from the tip or side of the hyphae Only seen with a microscope
26
What are the two forms of conidiospores used to identify the fungus
Microconidia Macroconidia
27
What are microconidia
Spore made up of a single cell
28
What are macroconidia
Multicellular spore, the entire unit breaks off to form a new fungus
29
Describe sexual reproduction of fungi
Done through meiosis -allows genetic variation Triggered by change in environmental conditions Requires 2 spores -can be from the same mycelium or different ones
30
Describe what happens If the two spores are from the same mycelium or different ones
Same: no genetic variation Different: genetic variation
31
What are the 3 stages in sexual reproduction
1) Plasmogamy: two haploid cells fuse and mix their cytoplasm and organelles (results in one large cell with 2 nuclei) 2) karyogamy: the 2 haploid nuclei fuse to form a diploid nucleus 3) meiosis: the chromosomes randomly sort into two different spores (haploid)
32
Describe fungal spores
Easily spread in the wind/air due to very small size Very difficult to destroy (resistant to all detergents, most chemical disinfectants, drying, heat and extreme cold) Standards of sterilization are designed to be able to destroy fungal spores and bacterial endospores
33
Define mycoses
Fungal diseases
34
Define mycology
Study of fungal diseases
35
Fungal diseases can be due to (2)
1) infection by the fungus | 2) exposure to fungal toxins (toxin from fungus)
36
Describe fungi
Ubiquitous in the environment Most are saprophytic and non pathogenic Many are transmitted via fomites (inhaled spores or hyphae when digging in soil) Can be part of normal flora in; skin, ears, oral cavity, GIT, urogenital tract
37
What are the 4 types of mycoses
Superficial mycoses (dermatophytoses -ringworm) Opportunistic mycoses Systemic mycoses Mycotoxicosis All have zoonotic potential and cause similar diseases in humans
38
Describe Antifungals
Drugs used to treat fungal infections Have more side effects because fungi are eukaryotic (like animal cells) Antifungals only work on replicating cells -cannot treat spores
39
Describe superficial mycoses
Commonly seen, infections of epidermis, hairs, nails Rarely spread to underlying tissue Secrete extracellular enzymes that breakdown keratin to use for nutrients Seen in cattle/horses/cats/dogs/people
40
What are common fungal agents
Microsporum Trichophyton
41
What are diagnostic tests for dermatophytes
Wood’s lamp test Tape sample of skin/hair fungal culture: dermatophyte test medium and routine fungal cultures
42
What is the wood’s lamp test?
Approx 50% of microsporum canis will fluoresce under UV light Never a definitive test Lots of false negatives: 50% do not fluoresce (trichophyton never fluoresce Lots of false positives: purulent discharge, certain dyes and conditioners fluoresce
43
How do you take a tape sample
Using scotch or packing tape, press over lesion (take skin and hair) Perform an in clinic microscopic examination with simple stain for spores
44
How do you prep for collecting clinical samples for culture (hair/skin scrapings)
Wear gloves Wipe affected area with 70% alcohol to remove bacterial contamination and medications Always take samples from OUTER margins of the lesion where the fungus is actively growing
45
How do you collect hair samples for cultures
Hairs should be pulled/plucked out (NOT cut) If wood’s lamp test is positive, take fluorescent hairs If there are broken hairs, take the broken hairs
46
describe skin scrapes and crusts for culturing
Always Collect any crusts Can perform superficial skin scraping of the affected area (from the edge of the lesion on the red border, use the blunted scalpel blade and no mineral oil)
47
Describe toothbrushing for spores
Use a new toothbrush (medium to hard) Brush all over hairs to collect spores Submit the whole toothbrush for testing
48
How do you transport cultures
Place in dry sterile container such as a sealed envelope (tape shut do not lick) or sterile container No plastic bags -moisture can cause bacterial overgrowth Keep at room temperature (fungi need to be room temp, bacteria need to be cold)
49
What are the 2 methods of culturing dermatophytes
Routine culture on supportive media -cultures all types of fungi Dermatophyte test media (DTM) (supportive/differential): specific to grow trichophyton and microsporum. Produces easy to recognize colonies and contains dyes that turn red/pink in the presence of exoenzymes secreted by dermatophytes
50
How do you inoculate DTM
Place hair and skin scraping onto media (push toothbrush into media) Seal the container to prevent media from drying out (depending on how long it will be stored and type of container, some fungi need oxygen to survive) Leave at room temp and in the dark Takes up to 3 weeks
51
Describe a positive DTM test How long do you have to wait to see a positive result? A negative one?
Media turns RED and colonies are white and fluffy Minimum 9 days for a positive culture on regular DTM minimum 2 days for a positive culture on rapid DTM (lots of false positives) Negative cultures must wait 3 weeks to confirm
52
How do you prevent the spread of ring worm
Zoonotic Wear gloves wipe exam tables with damp cloth to prevent dispersal of spores Clean equipment (disinfecting agent with fungicide claims) Vaccum repeatedly (do not sweep) Mop with a Disinfectant
53
Describe opportunistic mycoses Give examples of 3
Require either: 1) very large inoculum (lots of spores) 2) immunosuppressed host Ex. Aspergillosis, candidiasis, malassezia
54
Describe aspergillosis (genus) fungi
Common in the environment, not in normal flora Opportunistic -not very pathogenic All species are susceptible to it Most commonly affect the respiratory tract; lungs (mycotic pneumonia), nasal cavities (nasal aspergillosis), guttural pouch (guttural pouch mycoses, also leads to cranial nerve and carotid artery infections) Can also cause abortions and mastitis
55
Describe Candida (genus) fungi
Yeast Normal flora of URT, GIT, genital mucosa Opportunistic infection occurs with immunocompromised patients or if antibiotics remove competing bacteria Common infections sites in dogs; oral cavity, MM in the UGT Soft white growth over the surface Can cause severe systemic infections or oral thrush
56
Describe malassezia (genus)
Yeast Normal flora of skin and ears Opportunistic infection Overgrowth occurs if moist and hot or if antibiotic therapy removes competing bacteria Common infection in ears, skin and feet Diff quick swab analysis shows characteristic bowling pin shapes of budding
57
Describe systemic mycoses
Infections of the internal tissues/organs Transmission is usually by inhalation of spores Severe, difficult to treat, life threatening Most common in southern Saskatchewan: blastomycosis
58
What is blastomycosis
Infection caused by blastomyces dermatitidis This is endemic in North America, Great Lakes and Regina Found in yeast and mycelium forms Mycelium and spores are located in the ground in decaying vegetation (dogs inhale when digging) Always found in yeast form in clinical samples Primary pathogen Zoonotic Most commonly causes pulmonary infections (can spread to skin and eyes)
59
What is mycotoxicosis | AKA fungal toxicosis
Fungi can produce toxins which can remain in the cell or be secreted into the environment (contamination of feed with mould or mushroom/compost ingestion) Most are resistant to heat and chemicals Severe disease: GI effects, neurotoxins, cardiotoxins, hallucinogens, carcinogens, anaphylactic reactions
60
What is mouldy sweet clover
Certain legumes (sweet clover) produce a chemical called coumarin Coumarin is converted by mould into dicoumarin If dicoumarin is ingested by cattle it binds to vitamin K, which prevents clotting processes and increases fatal risk of bleeding
61
What is Ergot
Disease caused by claviceps prupurea Mould infects rye, barley, wheat, oats, grasses Mould produces toxins that cause disease when ingested. See; - vasoconstriction (most common) which decreases blood flow to tissues and causes necrosis - neurological disease - abortion

Microbiology (12 decks)

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