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Microbiology > Types Of Media > Flashcards

Types Of Media Flashcards

1
Q

Why do we cultivate bacteria

A
  • grow and isolate bacteria in an infection
  • definitive identification and characterization
  • determine which bacteria is causing infection
  • determine which bacteria is a contaminant or colonizer
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2
Q

Why should you obtain sufficient clinically relevant bacteria

A

1 test antimicrobial susceptibility
2 measure response to treatment
3 characterize agent
4 bank stain for future use

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3
Q

2 practical Problems of bacteria cultivation

A

1 choice of suitable medium - ideal environment to grow bacteria

2 isolation of a bacteria in pure culture - separate it from the rest

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4
Q

3 general situations in cultivation

A

1 to amplify defined bacteria clone with purpose or increasing amount produce

2 to quantify and identify types of organism in specimen

3 isolate a particular type of microbe in specimen from rest

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5
Q

Describe characteristics of non-fastidious bacteria and example

A
  • grow with few restrictions
  • need minima nutrients and growth factors

-E Coli used in routine gene amplification and protein production

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6
Q

Describe characteristics of fastidious bacteria , special conditions needed and example

A
  • require specific growth conditions that stimulate their natural conditions
  • have numerous restrictions
  • may require extract of host tissue to include all growth factors
  • needs suitable source or nutrients

Obligate intracellular bacteria: chlamydia and rickettsiae require viable eukaryotic cells to grow in and we infect eukaryotic cell to amplify them

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7
Q

What is micro biome

A

-total population of bacteria in a given specimen due to numerous micro environments supporting diff microbes

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8
Q

How do we identify diff microbes in a diverse specimen

A

-we set up numerous cultures with conditions to favor the diff conditions for the diff microbes found

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9
Q

What are the objects of design of a media

A

1 grow pathogenic bacteria of interest

2 separate of interest microbe from rest by inhibiting growth of ones we don’t want

3 differentiate their phenotypic properties for proper identification

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10
Q

Culture media categorized as

A

1 chemical - where chemical composition is known for specific media

2 complex - has extracts and digests of plants , meats of yeast when for bacterial growth

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11
Q

List the main types of media

A

1 liquid
2 solid
3 semi solid

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12
Q

Describe liquid media characteristics and how growth is determined

A

1 has a defined salt concentration
2 has source of protein ( peptone or casein )
3 fastidious require growth factors to be added
4 aka broth media
5 growth determined by increase in opacity ( turbidity )

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13
Q

Describe solid media characteristics , agar and how growth is determined

A
  • it’s broth media which is solidified by seaweed extracts called agar
  • agar is a complex polysaccharide , not metabolized by bacteria , liquified at 100 and solidifies at 40
  • growth identified as colonies
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14
Q

What is a colony and CFU

A
  • population of cells arising from one cell or spore

- single cell or spore from which a population of identical cells arises

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15
Q

Describe the characteristics of semi-solid media characteristics and use

A

-prepared with agar conc of less than 0.5%
Used to
1 determine bacterial motility
2 cultivation of microaerophilic bacteria

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16
Q

Uses of routine lab media

A

1 to enumerate
2 remunerate
3 isolate diff bacteria

17
Q

List the types of routine media in labs

A 
1 basal 
2 enriched 
3 enrichment 
4 storage 
5 transport 
6 selective 
7 differential 
8 anaerobic
18
Q

Describe characteristics and function of basal media

A
  • most basic
  • used for growth of non-fastidious bacteria
  • used for primary isolation of microbes

Nutrient broth
Nutrient agar
Peptone water ( most basic )

19
Q

Describe nutrient agar basal media , components and function

A
  • peptone / source of N2
  • beef extract / salts , carbohydrates, organic N2 compounds

Used for
1 enumeration of organisms in water, sewage , waste and dairy specimen
2 cultivation and maintenance of non-fastidious species

20
Q

Describe characteristics and function of enriched media and types

A
  • addition of extra nutrient to basal in form of blood, serum or egg yolk
  • used for fastidious bacteria eg haemophilus , influenza

1 chocolate agar
2 blood agar
3 Dorset egg

21
Q

Describe characteristics , components and function of blood agar and examples of bacteria in play

A
  • peptone / growth for non-fastidious bacteria
  • casein soy meat / growth of fastidious
  • NaCl / nutrient reserve
  • blood ( sheep or horse )/ nutrients, support haemophilus , neisseria
  • allow for detection of haemolytic organisms eg streptococcus or staphylococcus
22
Q

What is hemolysis and how do bacteria cause it

A

-streptococcus or other haemolyzing bacteria release hemolysins into agar that destroy and denature erythrocytes and hemoglobin to change the color

23
Q

Describe alpha hemolysis , color, cause and example of bacteria

A
  • partial lysis of RBC
  • greenish Grey or brownish discoloration around colony
  • hemoglobin reduced to methemoglobin

Streptococcus pneumonia

24
Q

Describe beta hemolysis , color, cause and example of bacteria

A
  • complete lysis of RBC
  • clear zone in medium

Streptococcus pyogenes
Streptococcus agalactiae

25
Q

Describe gamma hemolysis , color, cause and example of bacteria

A
  • no lysis

- no change in medium

26
Q

Describe chocolate agar components, function and use

A
  • has peptone, casein soy meat NaCl and blood

- blood added to hot agar causing RBC to lyse and release growth factors 5 and 10 and give rich brown color

27
Q

Fucntion of chocolate agar growth factors

A

-key support for haemophilus and neisseria

28
Q

Description and function of selective and enrichment media

A
  • designed to inhibit unwanted commensal bacteria

- help / encourage of interest bacteria to grow

29
Q

Describe properties of selective media and function and examples

A
  • soild ( agar based )
  • isolation of individual colonies
  • made selective by inhibitors that affect commensal agents and not of interest one

Thayer Martin agar
MacConkey agar
Mannitol salt agar
TCBS agar

30
Q

differential growth suspension

A

differential growth suspension - suppresses growth of one at expanse of another

31
Q

Describe properties, components and functions and examples of enrichment agar

A
  • liquid
  • to increase conc of at interest microbe whilst inhibiting others prior to plating on solid media
  • inhibitory factors suppress commensal

Alkaline peptone water
Vibrial cholera
Selenite F broth - stool pathogens eg salmonella

32
Q

Describe properties, components and use of MacConkey agar , mode of action and example of bacteria in play

A
  • selective differential medium of enterobacteriaceae from specimens
  • has bile salts and crystal violet ( inhibit gram +ve )
  • neural red indicator ( pH 6.8 and red )

-has lactose
-fermenter bacteria will ferment lactose to lactic acid reduced pH and indicator goes pink
( k pneumonia, enterobacter )

-non fermenter won’t change color
( salmonella , shigella )

33
Q

Describe properties, components and uses of transports media and examples

A
  • can be liquid , solid , semi solid or basal with additives that maintain viability of organisms while inhibiting growth of more Robust organisms
  • used to transport specimen from source to lab

1 Stuart’s media
2 amies media
3 Cary blur transport media

34
Q

Describe properties, components and uses of differential media and examples

A
  • has substrates metabolized by bacteria and by products impose unique color on colony
  • allow growth of more than one microbe but with morphological changes

TCBS
Blood agar
MacConkey agar
Mannitol salt agar

35
Q

Examples of anaerobic media and components

A
  • Robertson cooked meat medium
    /2.5 cm bullock heart meat
    / 15 ml nutrient broth

-Thioglycolate broth
/ sodium thioglycolate
/yeast extract
/casein hydrolysate

36
Q

How is O2 removed in anaerobic media and how is reduced O2 measured

A
  • boil to remove O2 and seal with sterile liquid paraffin
  • add 0.1% glucose , 0.1% thioglycolate , 0.1% ascorbic acid , 0.05% cysteine or red hot iron fillings

-used methylene blue indicator
/ colorless under reduced conditions

37
Q

Purpose of anaerobic media

A

-to provide media with low O2 and reduced oxidation-reduction potential and extra nutrients to anaerobes

Microbiology (5 decks)

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