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Microbiology 251 > Controlling Microbial Growth > Flashcards

Controlling Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

What are three methods for controlling microbial growth?

A

Physical, chemical, and antibiotics

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2
Q

Sterilization

A

Destruction of all forms of microbial life including bacterial spores

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3
Q

Disinfection

A

Destruction of microbial pathogens on an inanimate object. Bacterial spores may remain alive

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4
Q

Antisepsis

A

Destruction of microbial pathogens on living object

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5
Q

Sanitization

A

Reduction in the number of pathogens to a level deemed safe by public health guidelines

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6
Q

Inhibition

A

Effectively limiting microbial growth; not necessarily killing of the germ

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7
Q

Decontamination

A

Treatment of an object to make it safe to handle. Process of disinfection or antisepsis

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8
Q

Germicide

A

Any agent that kills microorganisms

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9
Q

Bactericide

A

Any agent that kills bacteria

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10
Q

Fungicide

A

Any agent that kills fungus

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11
Q

Viricide

A

Any agent that kills virus

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12
Q

Bacteriostatic agent

A

Agent prevents further multiplication, not necessarily kill all that are present

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13
Q

What are some factors that affect the efficacy of germicide?

A

TEMPERATURE (more effective at high), TYPES OF MICROORGANISMS (depends on composition of the cell wall, presence or absence of capsule), and ENVIRONMENT (presence of organic material reduces germicidal activity)

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14
Q

Thermal death point

A

Lowest temperature at which all microorganism are killed in 10 minutes

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15
Q

Thermal death time

A

Minimum amount of time required to kill all microorganisms at a given temperature

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16
Q

Decimal reduction time (D-value)

A

Time required for the destruction of 90% microbial population at a given temperature

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17
Q

What is the most widely used method of controlling microbial growth?

A

Heat sterilization

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18
Q

What can happen at high temperature?

A

Three dimensional proteins revert to an irreversible two dimensional structure. Some bacterial create endospores, but vegetative cells die

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19
Q

Dry Heat

A

Used in incineration devices, Bunsen burner, hot-air oven. Sterilization achieved in hot air oven at 170 degrees Celsius in 2 hours.

20
Q

What are the three moist heat methods?

A

Boiling water, autoclave, and pasteurization

21
Q

What does boiling water do?

A

Kills microorganisms at 100 degrees Celsius within 2-3 minutes if they are vegetative. But over 2-3 hours to destroy spores

22
Q

What does an autoclave do?

A

Uses steam (121 degrees Celsius) under pressure (15psi) and sterilization is achieved in 15 minutes

23
Q

What does pasteurization do?

A

Process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids. It does not kill all organisms, therefore, does not achieve sterilization

24
Q

What are the types of pasteurization?

A

Holding method, flash method, ultra pasteurization, HTST, UHT

25
Q

What does HTST stand for?

A

High-Temperature Short-Time

26
Q

What does UHT stand for?

A

Ultra-heat treatment

27
Q

What is holding flash method?

A

30 minutes at 62 degrees Celsius

28
Q

what is flash method?

A

15 seconds at 72 degrees Celsius

29
Q

what is ultra pasteurization?

A

3 seconds at 82 degrees Celsius

30
Q

What does HTST do?

A

Designed to extend the refrigerated shelf life of dairy products; 2-3 weeks

31
Q

What does UHT do?

A

135 degrees C for 1-2 seconds. Kills spores and it’s shelf life is up to 9 months.

32
Q

Tyndallization

A

Sterilization technique of liquids. Liquids are subjected to free steam for 30 minutes on each of 3 successive days

33
Q

What happens on the first successive day?

A

All vegetating microorganisms, except spores, are killed

34
Q

What happens on the second successive day?

A

In the overnight period, spores germinate and are killed on second day

35
Q

What happens on the third successive day?

A

The last few remaining spores germinate on the second evening and killed on the third day

36
Q

What are the four methods of heating process for sterilization of liquid media?

A

Boiling, autoclave, Pasteurization only if you use HTST, and tyndallization

37
Q

What are the non-heat physical methods of control?

A

Filtration, drying, lyophilization, cold temperature, radiation

38
Q

What does filtration do?

A

It avoids the use of heat on sensitive liquids and gases

39
Q

What are two types of filters?

A

HEPA and Membrane filters

40
Q

What does HEPA stand for?

A

High Efficiency Particulate Arrestance

41
Q

What does a HEPA filter do?

A

Type of air filter that removes particles less than .3 micrometers

42
Q

What does a membrane filter do?

A

Used for liquids, to remove bacteria, the pore size is .15-.22 and for viruses .01

43
Q

Drying

A

Water is removed from cells they shrivel and die

44
Q

What are two ways of drying?

A

Put in the cooler or heating the liquid to a lower temperature (ex. 60 degrees Celsius)

45
Q

Lyophilization

A

Liquid are quick-frozen and simultaneously subject to evacuation, dries the materials. vaccines are preserved this way

46
Q

Cold Temperature

A

Used in refrigerator to control growth. Microbial metabolism slows down and reproductive rate slows down.

47
Q

What are some ways that microbial growth can be reduced?

A

Microwaves, UV rays, X-rays, gamma rays, and electrons

Microbiology 251 (14 decks)

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