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1. Microbiology > Control of Microbial Growth > Flashcards

Control of Microbial Growth Flashcards

1
Q

What is sterilisation?

3

A

Complete destruction or elimination of all viable organisms

Killing or removal of all viable organisms

Includes the destruction of endospores

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2
Q

Through what two ways is the growth of microbes affected?

A

By killing microorganisms

By inhibiting the growth of microorganisms

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3
Q

What are the three ways to prevent microbial transmission?

A

Standard precautions e.g. hand hygiene

Transmission-based precautions

Surveillance - investigating and monitoring IPC practice

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4
Q

What are the two main types of agents used to control microbial growth?

A

Physical agents

Chemical agents

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5
Q

Give three examples of physical agents used to control microbial growth.

A

Heat

Radiation

Physical removal of cells

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6
Q

Give an example of a chemical agent used to control microbial growth.

A

Antimicrobials

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7
Q

What do antimicrobials do?

A

They kill or inhibit microbial growth

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8
Q

Give two examples of antimicrobials.

A

Disinfectants

Antibiotics

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9
Q

Where are disinfectants used?

A

In the environment

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10
Q

Where are antibiotics used?

A

In the human host

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11
Q

What are the three measures used to control growth in the environment.

A

Decontamination

Disinfection

Sterilization

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12
Q

What is decontamination?

A

Treatment that renders an object or inanimate surface safe for use or disposal

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13
Q

What is disinfection?

2

A

Destruction of vegetative organisms which might cause disease

Does not necessarily kill spores

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14
Q

What is considered the ultimate means of controlling microbial growth?

A

Sterilization

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15
Q

What are the two ways to control microbial growth in humans?

A

Antibiotics

Vaccines

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16
Q

What four methods of sterilization are used in the lab?

A

Red heat

Dry heat

Moist heat

Filtration - heat sensitive materials

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17
Q

What are the three methods of sterilisation in the Healthcare environments?

A

Moist heat

Radiation

Incineration

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18
Q

When is incineration carried out in a Healthcare environments?

A

It is used for the disposal of medical waste

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19
Q

When is radiation used in a Healthcare environment?

A

Used for drugs, tissue grafts and medical supplies

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20
Q

When is moist heat used in a Healthcare environment?

A

Autoclaving

Used for medical devices

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21
Q

What are the four most commonly used different methods of heat sterilization?

A

Red heat

Dry heat

Autoclaving

Incineration

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22
Q

Why should moist heat be used instead of dry heat where possible?
(2)

A

Moist heat has more penetrating power than dry heat

Moist heat produces a faster reduction in the number of living organisms

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23
Q

What temperature is needed to kill endospores?

A

121 degrees for 5 minutes

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24
Q

Why must temperatures reach 121 degrees for five minutes during heat sterilization?

A

As endospores are more thermoduric than vegetative cells

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25
Q

What are the three time periods involved in heat sterilization?

A

Heating-up period

Holding period

Cooling down period

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26
Q

What is the heating-up period?

A

The time needed for the entire load to reach sterilizing temperature

27
Q

What is the holding period?

A

The time for sterilization to occur

28
Q

What is the cooling down perios?

A

The time for the load to cool down

29
Q

Where is the only place where red heat is used in sterilization?

A

In micro labs

30
Q

Where is dry heat sterilization primarily used?

A

In the micro lab

31
Q

What is used to perform dry heat sterilization?

A

A hot air oven

32
Q

What is a hot air oven?

2

A

A thermostatically controlled oven

Fitted with a fan to ensure even temperature

33
Q

Can dry heat be used to sterilize?

A

No

34
Q

Why can’t dry heat be used to sterilize?

3

A

Sterilization time is too high

Higher temperatures are needed (160-170)

Too long and high for media

35
Q

What is dry heat used for?

3

A

Glassware

Metal

Objects that won’t melt

36
Q

Why is an autoclave used in the microbiology lab?

6

A

Sterilize culture media

Sterilize reagents

Sterilize equipment before use

Safe discard biohazardous wate

Safe discard of specimens

Safe discard of agar plate

37
Q

What exactly is autoclaving?

A

Steam under pressure at temperatures above the boiling point of water

38
Q

List some of the different types of autoclaves.

2

A

‘Pressure cooker autoclave’

Gravity displacement autoclave

39
Q

What is a pressure cooker autoclave?

2

A

A metal chamber with a strong metal lid

An air/steam discharge tap

40
Q

What is a gravity displacement autoclave?

4

A

Outer jacket filled with steam under pressure

Inner chamber - steam enters this chamber and forces the air out be gravity displacement

A thermocouple probe is inserted inside the chamber and around the load to monitor the load temperature

Interlocking devices prevent the opening of the door until temperature of load has fallen

41
Q

Where are gravity displacement autoclaves used?

2

A

Diagnostic labs

Healthcare CSSD

42
Q

What needs to be remembered when using an autoclave?

3

A

Materials must be packaged loosely

Sterilisation wrap or autoclave bags must be used to allow steam penetration

Autoclave indicator tape must be applied

43
Q

How does autoclave tape work?

2

A

Tape has diagonal markings made with temperature sensitive ink

Black stripes will become visible when the correct temperature is reached

44
Q

What is incineration used for?

A

The safe disposal of hazardous and high risk clinical waste

45
Q

What is filter sterilisation?

A

The physical removal of microorganisms from the air or liquids (does not trap viruses)

46
Q

When are membrane filters used?

A

For sterilization of heat-sensitive liquids e.g. antibiotic solutions

47
Q

How are membrane filter used?

A

Solutions are passed through a filter of sufficient pore diameter to remove the smallest known bacterial cells

48
Q

What type of radiation is most used in sterilisation?

A

Electromagnetic radiation

49
Q

Name the two different types of electromagnetic radiation used in sterilization.

A

Ultraviolet radiation

Ionizing radiation

50
Q

How does UV radiation work?

A

UV lamps cause the break in DNA

51
Q

Where is UV radiation used?

A

Used for workspaces and tools used in microbiology labs and healthcare facilities

52
Q

What are the disadvantages of UV radiation?

2

A

It only decontaminates surfaces

Microbes can be shielded from UV in fissures, cracks and shaded areas

53
Q

What are the benefits of ionizing radiation?

A

Gamma rays are highly effective in killing microorganisms and do not have sufficient energy to impart radioactivity

54
Q

How does ionizing radiation work?

A

Gamma rays degrade DNA and protein

55
Q

When is ionizing radiation used?

A

Widely used for sterilization in Healthcare facilities

56
Q

What are disinfectants?

A

Chemicals used to kill microbes but not necessarily their endospores on inanimate objects or surfaces

57
Q

Where are disinfectants used?

4

A

Microbiology lab

Hospital environments

Food industry

Drinking water

58
Q

Why are disinfectants used in the microbiology lab?

A

For safe discard and to decontaminate surfaces

59
Q

Why are disinfectants used in the hospital environment?

A

To decontaminate surfaces and heat sensitive materials

60
Q

Why are disinfectants used in food industry?

A

To reduce microbial load and make surfaces safe to handle

61
Q

What are the seven limitations of disinfectants?

7

A

Susceptibility of microorganisms to disinfectants varies

Endospores are generally resistant

Inactivated by clinical materials such as blood and plastics

Activity is reduced in the presence of large numbers or microorganisms such as biofilms

Must be made fresh daily

Must be made up at the correct concentration

May be sensitising and corrosive to skin

62
Q

Name three common disinfectants.

A

Virkon

TriGene

Hypochlorite

63
Q

How does hypochlorite work?

2

A

Activity due to chlorine

Very effective against, viruses and endospores

1. Microbiology (12 decks)

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