MIIM - Sterilisation, Disinfection, and Infection Control - Week 8

Question 1

Define aseptic technique.

Answer 1

Using procedures that minimise the transfer of micro-organisms.

Question 2

Define infection control.

Answer 2

Involves the prevention or minimisation of cross infections.

Question 3

Define cross infection (3).

Answer 3

The spread of micro-organisms from patient to staff, staff to patient, and patient to patient.

Question 4

List 5 risk factors for spreading infection in an optometric setting.

Answer 4

Removing foreign bodies
Assessing patients with ocular trauma or infection
Carrying out lacrimal lavage
Expressing glands and cysts
Fitting contact lenses

Question 5

Briefly mention some diseases that can be passed from patient to optometrist (13).

Answer 5

HIV
Hepatitis B and C
Measles
Mumps
Rubella
Varicella
Glandular fever
Herpes
Influenza
Adenovirus 8
CJD

Question 6

Define cleaning.

Answer 6

Removal of contaminating matter to lower the burden of organic material

Question 7

Define disinfection.

Answer 7

Removing from an article some or all of its pathogenic micro-organisms

Question 8

Define sterilisation.

Answer 8

Destruction or removal of all viable micro-organisms, spores, and other infectious agents from an article

Question 9

Define and describe the three categories of the spaulding classification system.

Answer 9

Critical - invasive devices that enter normally sterile tissue or the vascular system by intent or accident
Semi-critical - device contacts, but does not penetrate, mucous membranes
Non-critical - device only contacts skin

Question 10

Describe how to determine the initial contamination level of a sample.

Answer 10

Serially dilute the sample, spread on agar plates, incubate, and count colonies.
One colony represents one microbial cell.

Question 11

Describe how to determine the rate of biocidal action on a given pathogen.

Answer 11

Determine initial viable count
Expose to the agent
Repeat viable counts
Calculate the decimal reduction time

Question 12

Define decimal reduction time.

Answer 12

Time to reduce a population 10-fold at a particular temperature

Question 13

Define sterility assurance.

Answer 13

The probability that a micro-organism could survive a sterilisation process

Question 14

What is the relationship between the D-value and sterility assurance?

Answer 14

Descreasing linear

Question 15

Define what is meant by biocidal. Is it reversible or irreversible?

Answer 15

Processes or agents that kill micro-organisms and are irreversible

Question 16

Define what is meant by biostatic. Is it reversible or irreversible?

Answer 16

Processes or agents which inhibit microbial growth but are usually reversible.

Question 17

Name 4 main methods used for sterilisation.

Answer 17

Heat
Filtration
Ionising radiation
Chemical agents

Question 18

Differentiate between the effects of moist vs dry heat.

Answer 18

Moist heat coagulates
Dry heat oxidises

Question 19

What is more effective, moist or dry heat? Describe why.

Answer 19

Moist heat is more effective.
When steam condenses, it liberates intense latent heat.

Question 20

When would dry heat be used for sterilisation (6)?

Answer 20

Glass, metal, cutting instruments, powders, waxes, eye ointment bases

Question 21

When would moist heat be used for sterilisation (2)?

Answer 21

Most non-heat sensitive instruments, decontamination of used articles

Question 22

Name 4 advantages of dry heat.

Answer 22

Penetrates solids, usable on non-aqueous liquids, closed cavities, non-corrosive

Question 23

Name 2 advantages of moist heat.

Answer 23

Rapid and effective

Question 24

Name 3 disadvantages of dry heat.

Answer 24

Long times
Very high temperatures
Potentially very destructive

Question 25

Name 2 disadvantages of moist heat.

Answer 25

Corrosive over time Wets articles like wrappings

Question 26

Briefly describe how an autoclave works.

Answer 26

Its like a pressure cooker.

Question 27

Does filtration kill micro-organisms?

Answer 27

No, just removes them

Question 28

By what two processes does filtration work?

Answer 28

A combination of adherence and exclusion

Question 29

When are filters used?

Answer 29

For heat-sensitive liquids and air

Question 30

Describe the structure of depth filters and what they are made of (3). Do they have good flow?

Answer 30

Maze-like fibrous sheet or mat Can be made of paper, asbestos, or glass fibles Has good flow

Question 31

Describe the structure of membrane filters and what they are made of (2). Do they have good flow?

Answer 31

Large number of tiny holes like a sieve Made of cellulose acetate or nitrate Has good flow

Question 32

Describe the structure of nucleation track filters and what they are made of. Do they have good flow?

Answer 32

Has a small number of holes like a mat Made of very thin polycarbonate film, which is irradiated then etched Has low flow rate

Question 33

How does ionising radiation sterilise?

Answer 33

By creating free radicals which damage DNA

Question 34

Name three advantages of using ionising radiation to sterilise.

Answer 34

Effective at ambient temperature No wetting Articles packaged ready for use

Question 35

Name three disadvantages of using ionising radiation to sterilise.

Answer 35

High installation costs Safety issues Possible deleterious effects

Question 36

Give two examples of sterilising chemicals. Give an advantage and four disadvantages of these.

Answer 36

Gluteraldehyde and ethylene oxide Advantage - broad spectrum Disadvantage - slow, expensive, toxic residues, carcinogenic

Question 37

Name three kinds of indicators for monitoring the effectiveness of sterilisation.

Answer 37

Physical Chemical Biological

Question 38

Describe an example of a physical indicator for an autoclave.

Answer 38

A printer that contains the date, temperature, and time of sterilisation.

Question 39

Describe an example of a chemical indicator for an autoclave.

Answer 39

An autoclave tape which changes colour at a given temperature

Question 40

Describe an example of a biological indicator for an autoclave.

Answer 40

Spore strips which are placed into the autoclave as well and checked for viability

Question 41

Briefly describe the hazard analysis critical control points process.

Answer 41

A way to make a process more effective by identifying certain critical points in the process and monitoring them

Question 42

Name three disinfection methods.

Answer 42

Simple washing and cleaning Hot water/steam for shorter times Chemical disinfectants

Question 43

What is the aim of handwashing?

Answer 43

To remove transient flora

Question 44

Does handwashing eliminate resident flora?

Answer 44

No, it can only be reduced

Question 45

When should hands be washed (2)?

Answer 45

Before and after seeing a patient.

Question 46

Name 5 properties that an ideal handwash should have.

Answer 46

Broad spectrum Non-irritant Non-allergenic Rapid action Residual action

Question 47

What kinds of micro-organisms are the most susceptible to disinfectants (2)?

Answer 47

Vegetative bacteria Enveloped viruses (influenza/HIV)

Question 48

What kinds of micro-organisms are moderately susceptible to disinfectants (2)?

Answer 48

Acid-fast bacteria Non-enveloped viruses

Question 49

What kinds of micro-organisms are the least susceptible to disinfectants (4)?

Answer 49

Fungal and bacterial spores Protozoal cysts Prions

Question 50

Name two disinfectants with a broad spectrum.

Answer 50

Aldehydes and halogens

Question 51

Give three examples of disinfecting agents with a limited spectra.

Answer 51

Alcohols Phenols Chlorhexidine

Question 52

Name 5 factors that affect the efficiency of a disinfectant.

Answer 52

Concentration Contact time Temperature pH Presence of organic material

Question 53

Name a disinfectant that is effective in all situations.

Answer 53

None

Question 54

What is essential to disinfecting?

Answer 54

Thorough pre-cleaning

Question 55

Give an example of a halogen disinfectant and whether or not it leaves a toxic residue.

Answer 55

Hypochlorous acid Non-toxic residue

Question 56

What concentration are halogens used to clean tonometers and gonio prisms?

Answer 56

0.4-0.5%

Question 57

What is an alternative to chlorhexidine when broader spectrum is needed? Explain briefly how it works.

Answer 57

Iodophors Iodine is trapped in micelles and dispersed in a liquid colloid

Question 58

What is a disadvantage of iodophors?

Answer 58

Can cause contact dermatitis

Question 59

what concentration of hydrogen peroxide should be used to clean tonometers and gonio prisms?

Answer 59

3%

Question 60

Do alcohol water mixtures leave residual activity after evaporating?

Answer 60

No

Question 61

Are alcohol water mixtures effective against spores and cysts?

Answer 61

No

Question 62

What can prolonged exposure to alcohol water mixtures cause?

Answer 62

Drying

Question 63

What percentage of alcohol should be used for cleaning tonometers and gonio prisms?

Answer 63

70-80%

Question 64

What should be used on dirty surfaces?

Answer 64

Phenols

Question 65

What disinfectant is unaffected by organic material?

Answer 65

Phenols

Question 66

What is essential when using phenols?

Answer 66

Accurate dilution

Question 67

Are phenols effective against spores and non-enveloped viruses?

Answer 67

No

Question 68

What is chlorhexidine less effective against, gram positive or negative?

Answer 68

Negative

Question 69

Is chlorhexidine effective against spores and non-enveloped viruses?

Answer 69

No

Question 70

Does chlorhexidine leave residual or cumulative action?

Answer 70

Both

Question 71

Is chlorhexidine non-toxic?

Answer 71

Yes

Question 72

Is chlorhexidine non-irritant and non-allergenic?

Answer 72

Yes

Question 73

What two things affect the activity of chlorhexidine?

Answer 73

Anions and soaps

Question 74

What disinfecting agent is useful for gram-positive bacteria and non-enveloped viruses?

Answer 74

Quaternary ammonium compounds

Question 75

What are quaternary ammonium compounds easily inactivated by?

Answer 75

Organic matter