The Destruction of Microorganisms

Question 1

define decontamination

Answer 1

processes that remove or destroy contamination so infectious agents or other contaminants can’t reach a susceptible site in sufficient quantities to initiate an infection or other harmful response

Question 2

define sterilisation

Answer 2

the complete killing or removal of all types of microorganisms

Question 3

the 3 basic types of microorganisms

Answer 3

eukaryotes - fungi and protozoa

prokaryotes

viruses

Question 4

define disinfection

Answer 4

removing or destroying sufficient numbers of potential harmful microorganisms to make an item/surface safe to use

Question 5

define antisepsis

Answer 5

the practise of using disinfectants to damaged skin or living tissue

Question 6

define sanitisation

Answer 6

the removal of microbes that pose a threat to public health

Question 7

how can heat be used in decontamination? which two forms can it be used?

Answer 7

• can either be used in moist or dry form

moist: boiling, autoclave, exposure to steam

dry: oven, controlled temp cycles

Question 8

which is more effective? moist, or dry heat.

Answer 8

moist

Question 9

under moist and dry heat, what temp and times can c.botulinum spores be disinfected?

Answer 9

moist: 121° - 5 mins

dry: 160° - 2 hours

Question 10

what is an autoclave?

Answer 10

a device that uses steam to sterilise

Question 11

what are the 2 types of autoclaves?

Answer 11

Passive, Type N - for unwrapped instruments

Vacuum, Type B - for wrapped instruments

Question 12

what are 3 different cycles you can use for autoclaves? temperature and time

Answer 12

115° - 30 mins
121° - 15 mins
134° - 3 mins

Question 13

what test can you use to monitor the efficacy of autoclaves? what does it ensure and how does it work?

Answer 13

Bowie-Dick Test

• it ensures that all air is properly removed from the sterilisation chamber

how it works:
- use a heat-sensitive sheet
- sheet changes colour when exposed to certain pressures
- positive test that it works = sheet will be uniform in colour, no different colour stains

Question 14

disadvantages of dry heat

Answer 14

time consuming
energy consuming - higher temps required
may not be suitable for all materials

Question 15

what are some chemicals that can be used in sterilisation?

Answer 15

gas - ethylene oxide
liquid - glutaraldehyde, formaldehyde

alcohols - methanol, ethanol, isopropanol

chlorine and iodine - e.g. sodium hypochlorite and povidone iodine

Question 16

what is a side effect of using alcohol for disinfection?

Answer 16

it it dehydrating
can lead to disruption in cell membrane

Question 17

what caution should be taken with chemical disinfectants?

Answer 17

• clean the object first
• use the chemicals fresh
• use correct concentration
• do not mix with other chemicals

Question 18

when using chemicals, what should be considered?

Answer 18

• the effect is has on spores
• the corrosiveness
• where it is on the antimicrobial spectrum

Question 19

how can irradiation be used in decontamination?

Answer 19

• ultraviolet for surfaces
• gamma radiation for pharmaceuticals, medical and dental supplies

Question 20

what is gamma radiation also known as? how does it work?

Answer 20

cold sterilisation

• can pass through objects with high efficiency

Question 21

how can filtration be used in decontamination?

Answer 21

it removes microorganisms from liquids that are otherwise destroyed by heat

Question 22

describe thermal washers

Answer 22

they are good to use for disinfection
- use physical cleaning and thermal biocidal action

Question 23

which decontamination method is most appropriate in clinical situations?

Answer 23

low risk
- in contact with healthy skin
- not in contact with patients
= cleaning

mid risk
- contact with mucous membranes/body fluid
- contaminated with virulent or readily transmissible organisms
- use on immunocomprimised
= sterilisation or high level disinfection

high risk
- close contact with break in skin
- to introduce into sterile body site
= sterilisation

Question 24

describe disposable items.

Answer 24

they are single use/single patient
- should be labelled

require sterilisation before use
- usually via gamma radiation

Question 25

what are Transmissible Spongiform Encephalopathies? Give an example of one.

Answer 25

neurodegenerative disorders

Creutzfeld-Jakob Disease

Question 26

how is CJD caused, why is it so difficult to treat?

Answer 26

caused by prions in the brain - abnormal infectious protein

• prions are resistant to decontamination

Question 27

how is CJD infectious?

Answer 27

through neurological and lymphoid tissue
- through dental pulp = low risk