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Microbiology > Unit 9 > Flashcards

Unit 9 Flashcards

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
Q

What are conidiospores

A

Unicellular or multicellular spores that are released directly from the tip or side of the hyphae

Only seen with a microscope

26
Q

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

A

Microconidia

Macroconidia

27
Q

What are microconidia

A

Spore made up of a single cell

28
Q

What are macroconidia

A

Multicellular spore, the entire unit breaks off to form a new fungus

29
Q

Describe sexual reproduction of fungi

A

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
Q

Describe what happens If the two spores are from the same mycelium or different ones

A

Same: no genetic variation

Different: genetic variation

31
Q

What are the 3 stages in sexual reproduction

A

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
Q

Describe fungal spores

A

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
Q

Define mycoses

A

Fungal diseases

34
Q

Define mycology

A

Study of fungal diseases

35
Q

Fungal diseases can be due to (2)

A

1) infection by the fungus

2) exposure to fungal toxins (toxin from fungus)

36
Q

Describe fungi

A

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
Q

What are the 4 types of mycoses

A

Superficial mycoses (dermatophytoses -ringworm)

Opportunistic mycoses

Systemic mycoses

Mycotoxicosis

All have zoonotic potential and cause similar diseases in humans

38
Q

Describe Antifungals

A

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
Q

Describe superficial mycoses

A

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
Q

What are common fungal agents

A

Microsporum

Trichophyton

41
Q

What are diagnostic tests for dermatophytes

A

Wood’s lamp test

Tape sample of skin/hair

fungal culture: dermatophyte test medium and routine fungal cultures

42
Q

What is the wood’s lamp test?

A

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
Q

How do you take a tape sample

A

Using scotch or packing tape, press over lesion (take skin and hair)

Perform an in clinic microscopic examination with simple stain for spores

44
Q

How do you prep for collecting clinical samples for culture (hair/skin scrapings)

A

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
Q

How do you collect hair samples for cultures

A

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
Q

describe skin scrapes and crusts for culturing

A

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
Q

Describe toothbrushing for spores

A

Use a new toothbrush (medium to hard)

Brush all over hairs to collect spores

Submit the whole toothbrush for testing

48
Q

How do you transport cultures

A

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
Q

What are the 2 methods of culturing dermatophytes

A

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
Q

How do you inoculate DTM

A

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
Q

Describe a positive DTM test

How long do you have to wait to see a positive result? A negative one?

A

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
Q

How do you prevent the spread of ring worm

A

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
Q

Describe opportunistic mycoses

Give examples of 3

A

Require either:

1) very large inoculum (lots of spores)
2) immunosuppressed host

Ex. Aspergillosis, candidiasis, malassezia

54
Q

Describe aspergillosis (genus) fungi

A

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
Q

Describe Candida (genus) fungi

A

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
Q

Describe malassezia (genus)

A

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
Q

Describe systemic mycoses

A

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
Q

What is blastomycosis

A

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
Q

What is mycotoxicosis

AKA fungal toxicosis

A

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
Q

What is mouldy sweet clover

A

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
Q

What is Ergot

A

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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