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Microbiology Exam 2 > Lecture 13 > Flashcards

Lecture 13 Flashcards

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1
Q

Define disinfect

A

spores are not killed, but pathogens should be eliminated

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2
Q

Define sterilize

A

spores are killed along with vegitative cells, viruses, fungi, and protists

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3
Q

How can drug cocktails be made more effective?

A

mix drugs with very different modes of action

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4
Q

What is the method of choice in controlling microorganisms? Why?

A

heat sterilization

easy to control
leaves no residue
organisms can’t develop resistance

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5
Q

What is a disadvantage to using heat sterilization?

A

heat labile compounds are destroyed

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6
Q

Name the 2 types of physical methods to control microorganisms which involve heat

A

dry heat

moist heat

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7
Q

Define dry heat sterilization

A

stays dry the whole time
OR
ends up dry at the end of sterilization

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8
Q

Which is a faster process:

dry heat or moist heat sterilization?

A

moist heat

because proteins are more stable in dry heat

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9
Q

Name 2 different types of dry heat sterilization

A

Incineration

hot air oven

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10
Q

What happens during incineration?

A

very rapid oxidation of all organic material (organism burns)
heat speciment between 700-1500 degrees C
Only (inorganic) minerals left over

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11
Q

What is incineration used for? Give an example

A

biological waste disposal
EX:
Mad cow disease; incineration is the only certain way to get rid of the prions

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12
Q

What are prions?

A

amino acids which have folded incorrectly

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13
Q

Can you autoclave to remove mad cow disease?

A

Not really
one could autoclave the animal at 132 degrees for an hour, but the size and thickness of the cow would be difficult to assure full penetration

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14
Q

What is the mode of action of incineration?

A

Oxidation
Addition of oxygen = more intense oxidation
Removal of hydrogen = less intense (Protein oxidation)

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15
Q

What are the guidelines for time and temp of a hot air oven as a form of sterilization?

A

160 degrees C for 2 hours

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16
Q

How is the penetration of a hot air oven?

A

it has poor penetration

17
Q

What is the mode of action of a hot air oven?

A

dehydration- removal of water
protein oxidation- removal of hydrogen, mild
protein coagulation- protein falls out of solution and solidifies (the protein is destroyed) [for an example cook some eggs]

18
Q

Is moist heat sterilization slow or fast?

A

very fast

19
Q

Name 6 types of moist heat sterilization

A 
boiling
free flowing steam
steam under pressure
high volume autoclave
pasteurization
milk sterilization
20
Q

How can the boiling temperature of water be increased?

A

adding salt (NaCl or sodium carbonate)

21
Q

What does scrubbing do?

A

decreases load and washes off spores

22
Q

describe some characteristics of boiling

A

disinfects after 15 minutes

will kill spores after 5-9 hours

23
Q

Does boiling sterilize or disinfect?

A

disinfect

the time it takes to kill spores is too long to be considered a viable sterilization method

24
Q

What is the advantage of using free flowing steam?

A

less water log

25
Q

Does free flowing steam sterilize or disinfect?

A

disinfect

26
Q

does steam under pressure sterilize or disinfect?

A

sterilize

26
Q

Is steam under pressure more effective at killing microorganisms than a hot air oven?

A

yes

moist air at 121.5 degrees is more sterilizing than dry air at the same temperature

27
Q

What is an example of a way to sterilize using steam under pressure?

A

an autoclave

28
Q

What does pressure do that makes steam under pressure more effective than boiling?

A

the pressure raises the water temperature

29
Q

Are prions destroyed in a high vacuum autoclave?

A

no

30
Q

What is the goal of pasteurization?

A

destroying all pathogens while maintaining the most flavor of the sample

31
Q

What is the difference between batch and flash pasteurization

A

Batch is done in large quantites. Temp is lower (62.9), time is longer (30 minutes)
Flash is done in smaller batches at a hotter temperature (71.6) for a shorter amount of time (15 seconds)

32
Q

What does the batch method of pasteurization kill?

A 
Coxiella burnetti (Q-fever)
mycobacterium bovis (a form of TB)
33
Q

What is milk sterilization?

A

heat the milk to 140 degrees for less than a second

gives the milk a very long shelf life even without refrigeration

34
Q

What is the difference between milk sterilization and pasteurization?

A

Milk sterilization is done at higher temperatures (140 degrees) for less time (<1 second); does not taste good
Pasturization is done at a lower temperature for longer (time and temp vary by the method)

35
Q

What is the mode of action for moist heat?

A

protein coagulation

Microbiology Exam 2 (11 decks)

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