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Stage 2, Cycle 2 - Sterility and Asepsis > Sterilisation > Flashcards

Sterilisation Flashcards

1
Q

Define Sterility according to the OED

A

(When something is) Free from living microorganisms

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2
Q

Define Sterility according to Winfield and Richards

A

The total absence of viable microorganisms and an absolute state

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3
Q

Define Sterility according to Hugo and Russell

A

A product that doesn’t contain viable bacteria, yeasts or fungi nor other microorganisms such as protozoa, viruses etc

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4
Q

Define Achievable Sterility

A

The probability of microorganisms surviving should be low enough to ensure patient safety

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5
Q

What is the Sterility Assurance Level (SAL)

A

10 to the power -6. (One in a million chance)

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6
Q

Define D value (Decimal reduction time) in terms of heat sterilisation

A

Time taken at a fixed temperature to reduce the number of viable organisms by 90%

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7
Q

Define D value in terms of radiation

A

The radiation dose required to reduce the number of viable organisms by 90%

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8
Q

Z value applies to both heat sterilisation ad radiation. TRUE or FALSE

A

FALSE. Z value only applies to heat sterilisation

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9
Q

Z value assesses the influence of heat changes on ….?

A

Thermal resistance

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10
Q

What is Bioburden

A

The concentration of microorganisms in a material

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11
Q

To assure sterility, the bioburden must be as small as possible at the start of the process. TRUE or FALSE

A

TRUE

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12
Q

What is meant by Inactivation factor (IF) ?

A

The number of D values needed to achieve sterility assurance level

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13
Q

State the IF equation

A

10 to the power t/D

t = contact time or dose

D = D value

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14
Q

Heat sterilisation is the most reliable and most widely used method. TRUE or FALSE

A

TRUE

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15
Q

State one advantage of heat sterilisation

A

Destroys all enzymes and other essential cell components

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16
Q

State one ‘disadvantage’ of heat sterilisation

A

Can only be used with products that can handle the heat i.e: thermostable products

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17
Q

State the 2 types of heat used in heat sterilisation

A

1) Dry heat (for moisture sensitive products i.e: dressings)

2) Moist heat such as STEAM (for moisture resistant products)

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18
Q

Name the 3 stages involved in heat sterilisation

A

1) Heating stage
2) Holding stage
3) Cooling stage

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19
Q

What is the most commonly used method of terminal sterilisation

A

Moist heat sterilisation

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20
Q

State 6 products sterilised using moist heat sterilisation

A

1) Some dressings
2) Clothing
3) Equipment
4) Aqueous injections
5) Irrigation fluids
6) Opthalmic preparations

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21
Q

What equipment is commonly used for moist heat sterilisation ?

A

Autoclave

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22
Q

What is temperature range of an autoclave and how long for ?

A

121 - 134 degrees celcius

121 - 15 minutes
or
134 - 3 minutes

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23
Q

Shorter time in the autoclave causes less product damage and higher IF value. TRUE or FALSE

A

TRUE

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24
Q

Moist heat sterilisation causes ….. and …. of essential proteins?

A

Denaturation and Coagulation

therefore stop cells from replicating etc

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25
Q

Describe the F value

A

The mathematical method of converting time in the heating and cooling stage to time spent at 121 degree Celsius.

26
Q

What is the F value useful for ?

A

Products where holding time at 15 mins isn’t possible

27
Q

Dry heat sterilisation isn’t as commonly used as moist heat. Why ?

A

Higher temperature and longer exposure time; is needed for this process

28
Q

Dry heat sterilisation is mostly used in hospitals o surgical equipment. TRUE or FALSE

A

TRUE

29
Q

DHS is useful for sterilisation of glassware. How ?

A

DHS ensures depyrogenation as pyrogens stick to glassware

30
Q

Name a product sterilised using dry heat

A

Thermostable powders

31
Q

Non-aqueous thermostable liquids such as Alcohol is used in DHS. TRUE or FALSE

A

TRUE

32
Q

What equipment and temp range is used for DHS ?

A

Hot air oven. 160 - 180 degrees for up to 2 hrs

33
Q

What temperature and how long for is required for depyrogenation of glassware ?

A

250 degree Celsius, 45 minutes

34
Q

DHS has lethal effects due to oxidative processes. TRUE or FALSE

A

TRUE

35
Q

Name 2 types of gas used in Gaseous sterilisation

A

1) Ethylene oxide

2) Formaldehyde (not commonly used due to smell and risk)

36
Q

Gaseous sterilisation is generally used for temp sensitive items. TRUE or FALSE. Give examples of these items

A

TRUE;

  • Medical, diagnostic and electrical equipment used in operating theatres (microscopes, tubing etc)

-

37
Q

Formaldehyde and Ethylene oxide can be mutagenic and carcenogenic. TRUE or FALSE

A

TRUE

38
Q

Ethylene oxide can be detected by smell whilst Formaldehyde cannot. TRUE or FALSE

A

FALSE, it’s the other way round

39
Q

Gaseous sterilisation gases cause alkylation on what groups on proteins ?

A
  • Carboxyl, Hydroxyl, Amino and Sylphydryl

basically denaturation of protein

40
Q

Gaseous sterilisation gases cause alkylation on what groups on nucleic acids ?

A

Imino group

41
Q

What does Ethylene oxide have to be mixed with in order to be used?

A

Carbon dioxide (10%) OR HFC 124 (8.6%)

42
Q

Ethylene oxide mixed with more than 3.6% v/v of air will explode. TRUE or FALSE

A

TRUE

43
Q

Gases are good at penetrating materials. TRUE or FALSE

A

TRUE. e.g: raw powders

44
Q

800-1200mg/L at 45-6oC is the essential range for gases used for gaseous sterilisation. TRUE or FALSE

A

TRUE. Gas is left under this temp for around 4hrs

45
Q

Gas is let back out into the environment at the end of the sterilisation process. TRUE or FALSE

A

TRUE

46
Q

After gaseous sterilisation (using both ethylene oxide and Formaldehyde), products must be left for at least 24hrs to desorb toxins/toxic gas. TRUE or FALSE

A

TRUE

47
Q

Formaldehyde is a liquid. What is it mixed with to turn it into a gas ?

A

Water and heat with steam to 70-75oC; for around 4hrs

48
Q

Formalin contains what %w/v of formaldehyde

A

37% w/v

49
Q

State 3 methods of Radiation sterilisation and highlight the most effective

A

1) Accelerated electrons (Particulate radiation)
2) Gamma-ray (Electromagnetic radiation) - Most effective/least dangerous
3) UV light (Electromagnetic radiation) - least effective

50
Q

Gamma ray is usually performed on Industrial scale manufacture. TRUE or FALSE

A

TRUE

51
Q

State one ‘disadvantage’ of Gamma ray radiation sterilisation

A

Can damage aqueous solutions and certain types of packaging

52
Q

Gamma ray radiation sterilisation can be used on dry products such as ?

A

1) Surgical equipments
2) Plastic syringes
3) Dry powders
4) Dressings

53
Q

The D value of GRRS is connected to …… of radiation not the time ?

A

Dose

54
Q

What source is used for GRRS ?

A

Cobalt 60

55
Q

What is the half life of cobalt 60 ?

What is the standard dose of cobalt 60, i kGy ?

A

5.25 years

25kGy

56
Q

Define Disinfection

A

The process of removing microorganisms from the surface of inanimate objects

57
Q

State 6 types of Chemical agents used for disinfection

A

1) Alcohol (Most safe/least toxic)
- Aldehydes
- Halogens
- Peroxygens
- Phenolics
- Quaternary ammonium compounds

58
Q

State 2 types of biological indicators

A

1) Standardised bacterial spore preparations
2) Suspensions or Spores dried onto paper, plastic or Aluminium

  • Placed in with each load for sterilisation
  • Cultured after cycle has ended
59
Q

State the BI organism used in Moist heat sterilisation. State its D value and Log IF also

A

B. Stearothermophilus
D value - 1.5 mins
Log IF - 10

60
Q

State the BI organism used in Dry heat sterilisation. State its D value and Log IF also

A

B. subtilis var. niger
D value - 10 mins max
Log IF - Min. 12

61
Q

State the BI organism used in Irradiation sterilisation. State its D value and Log IF also

A

B. pumilus
D value - 3kGy
Log IF - 8.3

Stage 2, Cycle 2 - Sterility and Asepsis (4 decks)

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