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Microbiology > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

Culture/culturing (verb)

A

Process of growing bacteria in a lab

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2
Q

Reasons for culturing bacteria

A

To isolate different bacteria from a sample

To amplify number of cells

To indenting and characterize

To test for antibiotic resistance/susceptibility

For commercial reasons

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3
Q

Bacterial culture (noun)

A

Any population of bacteria grown and propagated under specific conditions in a lab/in vitro

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4
Q

Pure culture AKA monoculture

A

All bacteria in a culture are identical, therefore all originated from a single colony forming unit

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5
Q

Mixed culture

A

Contains 2 or more different bacteria (different genus/species or strain)

Indicated more than one colony forming unit present at the start

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6
Q

Sterile

A

Free of living organisms

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7
Q

Inoculation

A

The process of introducing a microorganism

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8
Q

Contamination

A

Unintentional or accidental introduction is microorganism(s)

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9
Q

Media

A

A liquid or gel designed to support growth of bacteria

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10
Q

Broth media

A

Liquid or pourable media

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11
Q

Solid media

A

Brother media that has been made into a solid with addition of gelatin or agar

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12
Q

Different media will be selected based on

A

Species cultures and reason for growing

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13
Q

Media types

A

Supportive (general purpose)

Enriched

Selective

Differential

Transport/storage

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14
Q

Supportive media AKA general purpose media

A

Supports the growth of many different organisms (not all)

Does not support growth of bacteria with strict requirements

Examples: luria broth (LB), trypticase soy agar (TSA)

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15
Q

Enriched media

A

General purpose media that has been supplemented to support bacteria that cannot grow on supportive media alone

Supplemented with different growth factors (amino acids, sugars, minerals, tissues)

Examples: blood agar, chocolate agar

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16
Q

Bacteria that can only grow on enriched media are termed

A

Fastidious (complex/complicated)

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17
Q

Why are selective and differential media important to clinical microbiology

A

Help indentifying which bacteria may be growing in a unknown sample

Can often identify genus and sometimes species

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18
Q

Selective media

A

Only grow SOME bacteria And not others, or inhibit others

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19
Q

Components of selective media

A

Antibiotics: allows only strains resistant to that antibiotic to grow

Different sugars: allow some bacteria with the metabolic enzymes to digest grow

Bile salts (MacConkey’s agar): selects for gram negative bacteria

Selenite, brilliant green dye: selects for salmonella

20
Q

Differential media

A

Allows many organisms to grow, but highlights differences between organisms

Differences related to metabolic pathways or toxin production

Contains dyes or substrates that are only metabolized by some bacteria

21
Q

Blood agar

A

Differential media

Used to differentiate between hemolytic and non hemolytic bacteria

22
Q

Transport and storage media

A

Most common

Maintains and protects bacteria for long periods of time

Does not allow bacteria to grow, or grows at minimal rate

23
Q

Why would we want to use transport/storage media

A

To prevent over growth and death phase, to have an accurate representative sample to look at later

24
Q

Trypicase soy broth (TSB)

A

Supportive/general purpose media

For growth

Adding agar produces solid trypticase soy agar (TSA)

25
Q

Blood agar

A

Trypicase soy agar (supportive media) with addition of 5-10% sheeps blood

Enriched and differential

Purpose:
Growth of pathogenic bacteria which are fastidious
Can determine if bacteria is hemolytic

26
Q

Hemolysis

A

Ability to lyse (damage) RBCs

Caused by bacteria that produce hemolysin (releases nutrients from RBCs for use by the bacteria cell)

These bacteria are pathogenic

27
Q

3 types of hemolysis

A

Alpha
Beta
Gamma

28
Q

A-hemolysis (alpha)

A

Partial hemolysis

Hemoglobin broken down to methemoglobin (greenish zone around the colony) (bruising)

29
Q

B-hemolysis (beta)

A

Complete hemolysis
Clear zone around the colony

B=best

30
Q

Y-hemolysis (gamma)

A

No hemolysis
Media stays red

“Y no break down man”

31
Q

Most important staining procedure in clinical microbiology

A

The gram stain (first step in identification)

Used to differentiate bacteria on basis of cell wall structure

32
Q

Primary stain

A

Stain that highlights specific structure that we are looking for

33
Q

Counterstain

A

“Non specific” stain that colors anything not bound by the primary stain

34
Q

Primary stain is

A

Crystal violet

Enters the cell wall and distributes throughout layers of peptidoglycan

35
Q

After the primary stain is

A

Treatment with iodine

Iodine bind to crystal violet(becomes a merger molecule that is trapped and cannot be washed away)

Structure being highlighted is the presence of multiple layers of peptidoglycan

36
Q

After iodine is

A

Alcohol wash (decolorizer)

Alcohol shrinks peptidoglycan layers in gram positive cells (crystal violet and iodine more tightly trapped)

Alcohol damages membrane of gram negative cells (crystal violet and iodine is realized from Periplasmic space)

37
Q

After alcohol wash is

A

Counterstain (Safranin or basic fuschin)

Stain enters the damaged outer membrane or gram negative cells and any other cells that don’t have crystal violet/iodine

Gram positive may take up some Counterstain but it is not visible against crystal viole

38
Q

Cell wall size and composition of gram positive cell

A

Thick

20-80 layers of peptidoglycan, teichoic acid

39
Q

Cell wall size and composition of gram negative cell

A

Thin

Outer membrane (lipopolysaccharides, phospholipids)
1-2 layers of peptidoglycan
40
Q

What color are gram positive cells after staining

A

Purple (crystal violet)

41
Q

What color are gram negative cells after staining

A

Pink/red (safranin)

42
Q

Are gram positive cells susceptible to penicillin

A

Yes

43
Q

Are gram negative cells susceptible to penicillin

A

No

44
Q

Are gram positive cells resistant to physical disruption by osmotic lysis

A

More resistant

45
Q

Are gram negative cells resistant to physical disruption by osmotic lysis

A

Less resistant

Microbiology (12 decks)

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