Destruction of micro organism: sterilisation and disinfection

Question 1

Define decontamination

Answer 1

Decontamination is a combination of processes that removes or destroys contamination so that infectious agents or other contaminants cannot reach a susceptible site in sufficient quantities to initiate infection or other harmful response

Question 2

Define sterilisation

Answer 2

Complete killing or removal of all types of micro organism (including spores)

Question 3

Give examples of micro organism

Answer 3

1. Eukaryotes
2. Prokaryotes
3. Viruses

Question 4

Define anti sepsis

Answer 4

Disinfection applied to damage skin or living tissues

Question 5

Define sanitisation

Answer 5

Removal of microbes that pose a threat to public health

Question 6

Give examples of sterilisation methods

Answer 6

1. Heat
2. Chemicals
3. Irradiation
4. Filtration

Question 7

How can we use heat to sterilise something

Answer 7

1. Moist heat

2. Dry heat

Question 8

What is the moist heat method of sterilisation

Answer 8

1. Boiling,
2. Autoclaving
3. Exposure to super heated steam at controlled press and temperature cycle

Question 9

Which is more effective autoclaving or boiling? Why?

Answer 9

Autoclaving as you can set the temperature and how long you want to sterilise something for eg 115 degrees at 30 mins or 134 degrees for 3 mins

Question 10

How do autoclaves work

Answer 10

The air displacement method

Question 11

Name the two sub types of the air displacement method

Answer 11

1. Passive (type N) for unwrapped instruments

2. Vacuum (type B) for wrapped instruments

Question 12

After sterilisation what is it important that we do?

Answer 12

Quality control to make sure the equipment has been sterilised properly

Question 13

Name some different methods we can evaluate the efficacy of an autoclave machine

Answer 13

1. The Bowie- Dick Test

Question 14

Name some problems that can occur in an autoclave and what they can cause

Answer 14

Air leakage
Unwanted condensation
These can result in cold spots which will mean the equipment isn’t properly sterilised

Question 15

Which of the 2:
dry heat exposure or autoclave saturated steam
Need a longer time to effectively sterilisation material

Answer 15

Dry heat needs longer
It runs t higher temperatures for a longer time Rame in comparison to autoclaves
Eg 160-170 degrees for 2 hours

Question 16

When is it better to use dry heat over moist heat to sterilise something?

Answer 16

1. When using metal as dry heat is not corrosive to metal

2. Some glass ware may get damaged in steam so better to use a dry heat method

Question 17

Give examples of gas chemicals we can use for sterilisation

Answer 17

Ethylene oxide

Question 18

Give examples of liquid chemicals we can use for sterilisation

Answer 18

Glutaraldehyde

formaldehyde

Question 19

Name the irradiation we use to sterilise equipment

Answer 19

1. Ultraviolet

2. Gamma radiation

Question 20

Describe Ethylene oxide and how we use it for sterilisation

Answer 20

It is a highly flammable gas
We usually mix it with 90% CO2 to prevent it from igniting
useful in killing spores and bulky items that can’t fit into an autoclave

Question 21

What is the main problem with Ethylene oxide?

Answer 21

It is highly flammable

Takes a long time to dissolve from surfaces so stays on the sterilised surface for some time after sterilisation

Question 22

Give some disadvantage of using Glutaraldehyde

Answer 22

It can become inactivated in the presence of organic matter

It is very toxic so not commonly used

Question 23

How is formaldehyde used?

Answer 23

Can be used in solution or as a vapour

Question 24

When is formaldehyde used?

Answer 24

When a large area has been contaminated or when contaminated equipment like extractor fans are hard to reach

Question 25

How does radiation get rid of microorganisms

Answer 25

It affects and breaks down their DNA leading to micro organism cell death

Question 26

When is ultra violet used as a sterilisation method

Answer 26

To sterilise surfaces or air

Question 27

What does ultraviolet not go through?

Answer 27

Glass due to its wavelength

Question 28

What is gamma irradiation sometimes referred to as?

Answer 28

Cold sterilisation

Question 29

What are gamma irradiations used to sterilise

Answer 29

Pharmaceuticals and medical and dental supplies | Equipment that can't be sterilised by other methods

Question 30

What is filtration

Answer 30

Removal of micro organisms from liquids that are destroyed by heat It does not destroy micro organisms but physically removes them

Question 31

What are membrane filters usually made out of

Answer 31

Nitro cellulose

Question 32

What is filtration usually used to sterilise

Answer 32

Liquids containing enzymes that could be denatured if they were heated (eg vaccines)

Question 33

If autoclaving is not useful what can we use?

Answer 33

Thermal washer disinfection

Question 34

What is thermal washer disinfection used to sterilise

Answer 34

Small dental equipments

Question 35

Is sub merging equipment into boiling water a good method for sterilisation?

Answer 35

NO it is not recommended by public health England

Question 36

Give examples of chemical disinfectants

Answer 36

1. Alcohol based 2. Chorine 3. Iodine

Question 37

Give examples of alcohols that can be used as disinfectants

Answer 37

1. Methanol 2. Ethanol 3. Isopropanol all

Question 38

Give examples of chlorine disinfectants

Answer 38

Sodium hypochlorite (bleach)

Question 39

Give examples of iodine disinfectants

Answer 39

Providone iodine

Question 40

Why is alcohol a good disinfectant?

Answer 40

As they dehydrate cells cause membrane disruption and cause co agulation of proteins

Question 41

Why is chlorine used as a disinfectant

Answer 41

As it prevents microbial growth in water supplies

Question 42

What is chlorine usually used to disinfect

Answer 42

Bodies of water like swimming pools | Used as bleach to clean up bodily fluids on surfaces

Question 43

When using chemical disinfectants what do we need to be cautious of?

Answer 43

1. Clean the object first 2. Make the chemical disinfectant fresh 3. Use the correct concentrations of disinfectant 4. Don't mix disinfectant with other chemical 5. Check the microbial spectrum 6. Check what effect the chemical disinfectant has on spored 7. May be corrosive and Double check fort hazards

Question 44

How are disposable items sterilised and what must they be labeled as?

Answer 44

Before use disposable items must be sterilised usually by gamma radiation They should then be labelled clearly as single use unless otherwise approved by the infection control team

Question 45

How do we determine if something needs to be sterilised, disinfected, washed or disposed of?

Answer 45

We create a risk assessment based on the planned usage and likely spectrum of micro organisms you wish to eliminate

Question 46

Describe the application of an equipment that would have a low risk assessment

Answer 46

It is in contact with healthy skin or not in contact with patients

Question 47

What is the recommended decontamination method for a low risk equipment?

Answer 47

Cleaning

Question 48

Describe the application of an equipment that would have a medium risk assessment

Answer 48

Equipment is: 1. In contact with mucous membrane or body fluids or 2. Contaminated by virulent or readily transmitted organisms or 3. For use on immunocompromised patients

Question 49

What is the recommended decontamination method for a medium risk equipment?

Answer 49

Sterilisation or high level disinfection

Question 50

Describe the application of an equipment that would have a high risk assessment

Answer 50

Equipment is inclose contact with a break in skin or mucous membrane OR Is needed for introduction into sterile body sites

Question 51

What is the recommended decontamination method for a high risk equipment?

Answer 51

Sterilisation

Question 52

How do we choose which method we should use to sterilise equipment?

Answer 52

Depends on the physical properties of the item itself and the properties of the packaging material

Question 53

What is chemical disinfection largely limited to?

Answer 53

1. Environmental decontamination or surfaces or spills 2, Antisepsis 3. Heat sensitive items

Question 54

Which of the methods of sterilisation is the least hazardous?

Answer 54

Heat is the least hazardous so should be used wherever possible

Question 55

As future clinicians what diseases should we be aware of and give examples

Answer 55

We should be aware of transmissible spongiform encephalopathies like Creutzfeld-jakob disease

Question 56

What are transmissible spongiform encephalopathies?

Answer 56

Neurological disease

Question 57

What is Creutzfeld-jakob disease caused by?

Answer 57

Prions that are highly resistant to decontamination

Question 58

What is another name for Creutzfeld-jakob disease

Answer 58

Mad cow disease

Question 59

How does Creutzfeld-jakob disease spread?

Answer 59

Through tissues or infected meat or unsterilised surgical instruments

Question 60

What risk group do dental scalers fall under?

Answer 60

High risk as they are used on patients

Question 61

How do we decontaminate dental scalers: | Sterilise, disinfect, wash or single use?

Answer 61

Washing and sterilisation

Question 62

How do we sterilise dental scalers?

Answer 62

Moist heat using an autoclave

Question 63

What risk group do dental drill holders (not the hand-piece) fall under?

Answer 63

Low risk as they don't touch the patient

Question 64

How do we decontaminate dental drill holders (not the hand-piece) : Sterilise, disinfect, wash or single use?

Answer 64

Washing and disinfection

Question 65

How do we wash and disinfect dental drill holders (not the hand-piece)?

Answer 65

Chemically using an azowipe (70% isopropyl alcohol)

Question 66

What risk group do hand-pieces fall under?

Answer 66

High risk

Question 67

How do we decontaminate hand-pieces | Sterilise, disinfect, wash or single use?

Answer 67

Washing and sterilisation

Question 68

How do we sterilise hand-pieces?

Answer 68

Moist heat using an autoclave

Question 69

What risk group do dental burs fall under?

Answer 69

High risk

Question 70

How do we decontaminate dental burs | Sterilise, disinfect, wash or single use?

Answer 70

Single use

Question 71

What risk group do Endodontics reamers and files fall under?

Answer 71

High risk with special risk for Creutzfeld-jakob disease

Question 72

How do we decontaminate Endodontics reamers and files | Sterilise, disinfect, wash or single use?

Answer 72

Single use