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Microbiology > Lab Quiz 4 > Flashcards

Lab Quiz 4 Flashcards

1
Q

What does zone of inhibition mean?

A

that a particular agent is microbicidal

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2
Q

what are bacteriophages?

A

viruses that attack bacteria

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3
Q

what is a plaque?

A

produces a clearing that can be view with the naked eye.

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4
Q

what is PFU?

A

Plaque forming unit

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5
Q

what is TNTC?

A

too numerous to count

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6
Q

what is TFTC?

A

too few to count

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7
Q

the number of plaque should fall between what numbers?

A

30-300

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8
Q

how to calculate the number of pfu’s per mL?

A

multiplying the number of pfu’s on a plate times the dilution factor of the phage placed on that plate

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9
Q

what time of phage are we using?

A

T2 or T4 coli-phage sample strain from E.coli

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10
Q

what life cycle T2 or T4 use?

A

lytic cycle

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11
Q

what is the lytic cycle?

A
  1. The virus attaches to bacteria (host)\ (attachment)
  2. The virus inserts its DNA into the bacteria (penatration)
  3. The virus takes over the cell’s machinery (biosynthesis)
  4. The virus reproduces itself and self-assembles.(Maturation)
  5. The host cell is destroyed(release)
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12
Q

why would you expect to find any streptomycin resistant mutants?

A

random chance

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13
Q

what is the purpose of the streptomycin?

A

To reduce the development of drug-resistant bacteria and maintain the effectiveness of streptomycin and other antibacterial drugs (selects resistant bacteria)

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14
Q

Does streptomycin induce mutations?

A

no

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15
Q

what are Coliform bacteria?

A

gram negative
non-spore forming
Facultatively anaerobic rods that ferment lactose

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16
Q

What are they used for?

A

enterics to indicate organisms for the possible presence other enteric pathogens such as Salmonella and Shigella.

17
Q

what is the most commonly used indicator organism?

A

E.coli

18
Q

potable water?

A

drinkable

19
Q

what is the recommended standards by the U.S. Public Health Service for drinking?

A

no more than 1 coliform per 100ml

20
Q

For total bacterial count?

A

no more than 100 bacteria/ml

21
Q

what are the advantages of filter method?

A
  • relatively fast
  • large volumes of water can be tested which would find relativity few contaminants (sensitive)
  • accuracy, each colony represents a clone of a single bacterium; results reproducible and quantitative
22
Q

what are the disadvantages?

A
  • turbidity clogs filter
  • highly contaminated water must be diluted in order to obtain discrete
  • countable colonies,
23
Q

What color is it for E.coli?

A

shiny green/gold

24
Q

what color for coliforms?

A

dark red/purple colonies

25
Q

what color for non-coliforms?

A

any other color

26
Q

How to calculate the number of coliforms?

A

divide the number of colonies counted by the mL of sample and multiply by 100
= #colonies/mLsample x 100

27
Q

Microbial Flora test:
What are the result for Staphlococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus in the Mannitol fermentation test?

A

Staphlococcus aureus= +, yellow agar, growth Staphylococcus epidermis= -, no yellow agar, growth Staphylococcus saprophyticus = -, no yellow agar, growth

28
Q

Microbial Flora test:
What are the results for Staphylococcus aureus, Staphylococcus epidermis, and Staphylococcus saprophyticus in the Coagulase test?

A

Staphlococcus aureus = +, clot forms
Staphylococcus epidermis = -, no clot
Staphylococcus saprophyticus = -, no clot

29
Q

Microbial Flora test:
What are the results for Staphylococcus aureus, Staphylococcus epidermis, and Staphylococcus saprophyticus in the Novobiocin Sensitivity test?

A

Staphylococcus aureus = susceptible (>=22mm zone) Staphylococcus epidermis = susceptible (>=22mm zone) Staphylococcus saprophyticus = resistant (<= 17mm zone)

30
Q

what causes cavities?

A

Lactobacilli and streptococci

31
Q

What does Lactobacilli and streptococci do?

A

ferment glucose to produce acids that erode tooth enamel and promote tooth decay leading to dental caries.

32
Q

What is pH of Snyder media?

A

4.8

33
Q

What bacteria and inhibit in Snyder media?

A

Lactobacilli and streptococci

34
Q

what type of media is this?

A

Snyder agar, contains 2% glucose and the pH indicator bromcresol green, tube agar

Microbiology (11 decks)

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