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MMI Intro >  Microbial Culturing > Flashcards

 Microbial Culturing Flashcards

1
Q

What should you consider when trying to collect specimens?

A

-Containers should be sterile with proper lids
- Specimens may need to be stored or shipped at specific temps
- details on labels are important
- other special instructs may apply
Ie) urine sample taken mid-stream

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2
Q

How fast does Escherichia coli double in?

A

17-20 minutes

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3
Q

What are cultures used for?

A

Identification/characterization of a microorganism, determining is abundance, fermentation products and scientific research

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4
Q

What is a mesophile?

A

Most organisms fit into this category. They grow between 20-40 degrees

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5
Q

What is a thermophile?

A

Likes heat: grows between 40-80 degrees

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6
Q

Listeria monocytogens grows best at _____________, but also grows well at _________________. It is known as a __________________, because it can grow in the _____________

A

30 degrees, colder 0 degrees, psychotrophic. Cold

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7
Q

What bacteria causes listeriosis

A

Listeria monocytogens

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8
Q

What is the leading cause of death among food borne bacteria pathogens and why?

A

Listeria monocytogens. It can grow in the cold and at 30 degrees.

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9
Q

How does listeria monocytogens infect?

A

Secretes invasion that enables the bacteria to penetrate the host cell and move to other tissues.

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10
Q

Define what an acidophiles, neutrophils, alkaliphile is.

A

Acidophiles: like acid: 1-5.5
Neutrophils: neutral: 5.5-8.5
Alkalphile: basic, 7.5-11.5

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11
Q

What pH do most fungi prefer?

A

Acidic ph ~5-6

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12
Q

What pH do most bacteria prefer?

A

~6-8

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13
Q

Give an example of a type of bacteria that can survive in your stomach.

A

Helicobacter pylori: associated with gastric ulcers and cancers

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14
Q

What is osmotic pressure (how salty)

A

Determines whether water will be trying to move or out of cell: can lead to dehydration or to cell exploding due to to high of water inside cell

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15
Q

What is an isotonic solution?

A

No water movement. Solutes in side and outside the cell are equal

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16
Q

What is a hypertonic solution?

A

There is more salt/solutes outside the cell than inside and water exists the cell

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17
Q

Give an example of a type of bacteria that likes a salty or hypertonic solution and where it lives?

A

Straphlococcus epidermis: lives on your skin which is salty

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18
Q

What is a halotolerant organism?

A

(Staphylococci) can tolerate salty envrionments

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19
Q

What are the most common chemical requirements?

A

Crabon: for organic molecules, energy source
N: aa,& NT
S: aa, thiamine, biotin,
P: DNA,RNA, ATP, phospholipid membrane
Organic factors: somthing that the organism can not produce on its own. Ie) vitamins
Trace elements: inorganic elements ie) Fe
O2: obligate, facultative: aerobes/anaerobes

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20
Q

What does reducing media do?

A

Contains chemicals that react with and remove 02 from the media

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21
Q

How to you obtain a single distinct colony in a culture in a lab

A

The easiest technique is streaking

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22
Q

What is a colony morphology?

A

Microbes can be defined on media (liquid or solid) by the colony colour, texture, shiny, translucent…

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23
Q

What is the purpose of streaking?

A

To isolate a pure strain from a single species of microorganism.

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24
Q

How do you culture virus?

A

You must first culture the host cell than can use the host cell to culture the virus.

25
Q

How do you culture bacteriophages?

A

They are grown on a bacterial lawn. The spots that are clear “plaques” are where the virus has grown.

26
Q

Where are animal virus cultured?

A

-Embryonated eggs
Ie) influenza is modified to grow in eggs, allows to culture for vaccine.
-Tissue/cell culture ie) polio virus
-living animals ie) HIV in modified mice., Nora virus (need human volunteers causes explosive Diaherria and vomiting)

27
Q

Why are procedures performed under sterile conditions?

A

1) To keep the culture pure and uncontaminated.

2) protect workers/lab

28
Q

What are the different types of growth media?

A
  • General/complex
  • chemically defined
  • enriched
  • selective
  • differential
29
Q

Explain what a general/complex media is:

A

-non-selective
-encourages the growth of a range of microbes
Ie) Nutrient Agar, TSA (trytic Soy Agar)

30
Q

Explain what a chemically defined growth media is:

A

The exact chemical composition is precisely known. ->often used to study genetic mutants

31
Q

What is an enriched media?

A

Non-selective-> contains additional factors needed to grow microbes with particular needs.
Ie) chocolate agar: has Lysed (typically sheep) blood so that the hemoglobin is exposed.

32
Q

What is a selective media?

A

Only supports the growth of specific microbes.
Often used to isolate a specific species.
Ie) pH of media to low for fungi to grow but not bacteria.
Ie)an antibiotic is added so that Pseudomonas aeruginosa can grow but E.coli can’t

33
Q

What is differential media?

A

The agar will allow for different appeared due to the characteristics of the media (turn different colours)
Ie)EMB (Eosin Methylene Blue) agar: provides a colour indicator distinguishing between organisms that ferment lactose (E.coli) and those that don’t ie) Samonella

34
Q

MacConkey Agar is used for what (Very important to know this!)

A

-isolate G (-)
-contains crystal violet stain (kills G (+), protein and neutral red dye. (Makes it selective)
-Differential: b/c the neutral red dye becomes red in the presence of the waste products of lactose metabolism.
The neutral red dye interacts with how acidic/basic it becomes.
Ie) E.coli = red
Salmonella = yellow

35
Q

What is Blood Agar used for?

A

To isolate pathogens with complex nutritional requirements and to detect hemolytic activity.

36
Q

How much blood does blood agar contain?

A

5-10% WHOLE sheep blood

37
Q

Why does blood agar need to be enriched?

A

It is enriched with blood to support the growth of additional microbes.

38
Q

What makes Blood Agar differential?

A

A clear ring is seen round colonies of bacteria which are cable of hemolysis (lysine red blood cell)
->good for streptococcus

39
Q

What are the different types of hemolysis:

A

Alpha- hemolysis
Beta- hemolysis
Gamma- hemolysis

40
Q

What is alpha-hemolysis and give an example.

A

Partial hemolysis-> appears greenish on agar.

Ie) Streptococcus pneumoniae

41
Q

What is Beta-hemolysis and give examples (2)

A 
Complete hemoloysis-> appears clear 
Group A (GAS): Streptococcus progenes (strep throat)
Group B (GBS): Streptococcus agalactiae (infectious to new borns)
42
Q

What is Gamma hemolysis and give an example.

A

No clearing (no-colour) (formily Group D): Enterococcus faecalis

43
Q

Besides growing conditons how else can you identify bacteria?

A

By Bacterial enzymes and by-products of metabolic processes.

44
Q

What is the Catalase test?

A

The catalase test is used to differentiate staphylococci (catalase +) from streptococci (catalase -)

45
Q

What does the catalase test do?

A

Bubbles of 02 gas are produced when peroxide is added to a smear of culture (catalase positive)
Catalse: H202 (peroxide)-> H2O +O2

46
Q

What is the coagulate test do?

A

Coagulase is an enzyme produced by Staphylococcus aureus that coverts soluble fibrinogen (human protein) in plasma to (insoluble) fibrin.

47
Q

How do you perform a coagulase test?

A

A drop of rabbit plasma is added to a smear of culture. Clumping of the plasma indicates coagulase-positive.

48
Q

What is the urease test do?

A

Proteus sp. produces urease. The specimen is placed in media containing urea and pH indicator. As urea is broken down it produces ammonia and raises the pH

49
Q

What is a rapid identification system?

A

Various systems are available…. typically allows multiple test to help identify an organism quickly.

50
Q

What is antimicrobial sensitivity testing:

A

Sometimes need to both identify both the organism and what antibiotic therapy may be effective.

51
Q

What do microbes grow in naturally as complex communities?

A

Biofilm

52
Q

What method to you use to get a pure culture?

A

Streaking

53
Q

How to you culture a virus cell?

A

Using host cells

54
Q

What are liquid & solid media, and why are they used?

A

Liquid: broth-> some things won’t form colonies. Ie) protist
Solid: agar: allows to isolate indivuial bacteria to grow pure colonies.

55
Q

Why must media, flask/tubes and instruments be sterilized before used for growing microbes?

A

To make sure there is no cross-contamination

56
Q

What are bacterial lawns used for?

A

To grow phages

57
Q

What types of chemical and physical requirements must be considered for culturing microbes?

A

Temp, pH, nutrient requirements, presence of 02

58
Q

How would you describe MacConkey agar and blood agar?

A

MacConkey agar:
Selective: uses crytal violet to kill G (+)
Differential: uses neutral red dye to distinguish the metabolism of lactose
E-.coli = red
Samonella = yellow
Blood agar:
Enriched: whole blood was needed.
Differential: clear ring/colour based on hemolysis of cell
Alpha: partial/green
Beta: complete/ clear
Gamma: non-hemolytic= no colour.

MMI Intro (7 decks)

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