Sterilisation & Disinfection

Question 1

What is sterilisation?

Answer 1

The killing of ALL forms of microorganisms, including spores.

Sterilisation is distinct from disinfection, which does not eliminate spores.

Question 2

What is disinfection?

Answer 2

Elimination or reduction of vegetative microorganisms, excluding spores.

Disinfection is often used in contexts where complete sterilisation is not necessary.

Question 3

What are the routes through which infection can be introduced into an organism?

Answer 3

• Systemic: medicine, surgery, instruments, dressings, injectables
• Oral: consumption of foodstuffs or medicines
• Local: application of products such as droplets, inhalers, or suppositories

Question 4

What is the importance of maintaining integrity during sterilisation or disinfection?

Answer 4

To prevent infection and preserve the characteristics of the item being sterilised or disinfected.

This is crucial in medical and laboratory settings.

Question 5

What are the performance considerations for autoclaves?

Answer 5

• Wrapping of items
• Load pre-infection
• Packing of load
• Moisture
• Time
• Temperature

Question 6

What is the required temperature and time for clean items in an autoclave?

Answer 6

121 degrees C for 15 minutes.

This is for clean items or media; waste requires higher temperatures.

Question 7

What is the required temperature and time for waste in an autoclave?

Answer 7

134 degrees C for 30 minutes.

Question 8

Why is moisture important in the autoclave process?

Answer 8

Dry air prevents sterilisation at autoclave temperatures.

Question 9

What biological indicator is used for autoclave performance?

Answer 9

Use of spore-forming microorganisms such as bacillus subtilis (requires culture).

Question 10

What physical parameters are monitored in autoclave performance?

Answer 10

Time, temperature, and pressure.

Question 11

What chemical measures are used to check autoclave performance?

Answer 11

Autoclave tape
Browne tape

Question 12

What type of indicator is used for hot oven performance?

Answer 12

Indicator tape specific for dry heat ovens.

Question 13

What are the physical parameters monitored in hot oven performance?

Answer 13

Time, temperature, and pressure.

Question 14

Fill in the blank: The host _______ refers to the microorganisms living in or on a host organism.

Answer 14

microbiome

Question 15

True or False: Sterilisation eliminates all forms of microorganisms, while disinfection only reduces vegetative microorganisms.

Answer 15

True

Question 16

What is the boiling point used in the boiling method for decontamination?

Answer 16

100°C

Question 17

Does boiling kill endospores?

Answer 17

No

Question 18

What are the two types of pasteurisation?

Answer 18

• Slow - 63-66°C x 30 minutes
• Rapid - 73°C x 15 seconds

Question 19

Who is pasteurisation named after?

Answer 19

Louis Pasteur

Question 20

What is membrane filtration?

Answer 20

Polymer films/membranes with microscopic pores

Viruses so small they can fit through filter though

Question 21

What is the pore size range for membrane filtration?

Answer 21

• 0.1 μm
• 0.22 μm
• 0.45 μm

Question 22

What pore size is required to filter yeast?

Answer 22

0.45 - 1.2 μm

Question 23

What pore size is required to filter bacteria?

Answer 23

0.2 μm

Question 24

What pore size is required to filter viruses and mycoplasmas?

Answer 24

0.01 - 0.1 μm

Question 25

What are some applications of membrane filters?

Answer 25

• Heat sensitive products
• Laboratory and industrial purposes (e.g. filtered milk)

Question 26

What are some disadvantages of membrane filtration?

Answer 26

• Saturation (clogging)
• Product retention

Question 27

What is depth filtration used for?

Answer 27

• Clarifying bulk products
• Reducing bio-burden
• Filtering viruses (nanofiltration)
• Reducing endotoxin

Question 28

What is a key consideration for filtration in sterilisation?

Answer 28

Filtration alone is not sufficient when sterilisation by other means in the final container is possible

Question 29

What is the recommended pore size for filters when sterilising solutions?

Answer 29

0.22 micron or less

Question 30

What should be done if it is not possible to use heat for terminal sterilisation?

Answer 30

Use a second titration

Question 31

What is ethylene oxide gas (ETO) used for?

Answer 31

Chemical sterilisation for items that cannot be sterilised by irradiation or moist heat

Question 32

What percentage of medical devices in the USA are sterilised with ETO?

Answer 32

Approximately 50%

Question 33

What are some hazards associated with ETO?

Answer 33

• Carcinogenic
• Teratogenic
• Mutagenic
• Can induce spontaneous abortion
• Volatile and Explosive

Question 34

How does ETO work in sterilisation?

Answer 34

By alkylation of protein and DNA

Question 35

What does disinfection involve?

Answer 35

Cleansing a wound or a room (surface/object), removing dirt and potentially infectiour organisms from an area/ object.

Question 36

What are antiseptics required to do?

Answer 36

• Clean dirt
• Kill microorganisms
• Be non-toxic to tissues

Question 37

What are key considerations in sterilisation and disinfectant procedures?

Answer 37

Dose and contact time

Question 38

Fill in the blank: The amount and time of the agent/method applied to ensure microorganisms are inactivated or killed is known as _______.

Answer 38

[dose and contact time]