Sterilisation

Question 1

What is sterilization?

Answer 1

Sterilization is a process of eliminating all forms of microbial life, including bacteria, viruses, and fungi, from an object or a surface.

Question 2

Why is sterilization important?

Answer 2

Sterilization is important in many settings, including healthcare, food production, and laboratory work, where it is necessary to prevent the spread of infectious diseases and ensure the safety and quality of products.

Question 3

What are some methods of sterilization?

Answer 3

Physical: Moist and Dry Heat
Irradation: Ionizing gamma and X Ray
Chemical: Ethylene oxid and Propylene Oxide

Question 4

What factors determine the choice of sterilization method?

Answer 4

The choice of sterilization method depends on the type of material being sterilized and the specific requirements of the application.

Question 5

Why is moist heat preferred sterilisation?

Answer 5

Steam under pressure is inexpensive and sterilises penetrable materials and exposed surfaces rapidly. Good heat transfer

Question 6

Name two different types of autoclave

Answer 6

Gravity displacement and Vacuum Autoclave

Question 7

What is a gravity displacement autoclave?

Answer 7

A gravity displacement autoclave is a type of steam sterilization device that uses gravity to circulate steam throughout the sterilization chamber.

Question 8

How does a gravity displacement autoclave work?

Answer 8

In a gravity displacement autoclave, steam is introduced into the sterilization chamber through a small vent at the top of the chamber. As steam enters the chamber, it displaces the cooler air inside, causing it to be forced out through a vent at the bottom of the chamber. This displacement of air by steam creates a circulation of steam throughout the chamber, which is necessary to ensure that all surfaces and materials are properly sterilized.

Question 9

What types of materials can be sterilized using a gravity displacement autoclave?

Answer 9

A gravity displacement autoclave can be used to sterilize a variety of materials, including laboratory glassware, surgical instruments, and medical supplies.

Question 10

What are some advantages of using a gravity displacement autoclave?

Answer 10

Some advantages of using a gravity displacement autoclave include its simplicity, low cost, and ability to sterilize a wide variety of materials. It also has a relatively short cycle time compared to other types of autoclaves.

Question 11

What is steam sterilization?

Answer 11

Steam sterilization is a method of killing microorganisms by exposing them to high temperature and pressure steam.

Question 12

How does steam sterilization affect microorganisms?

Answer 12

Steam sterilization affects microorganisms by denaturing their proteins and disrupting their cell membranes. The high temperature and pressure of the steam cause coagulation of proteins and denaturation of enzymes, ultimately leading to the destruction of the microorganisms

Question 13

What factors can affect the effectiveness of steam sterilization?

Answer 13

Factors that can affect the effectiveness of steam sterilization include the temperature and pressure of the steam, the duration of exposure, the presence of inhibitors or materials that can interfere with the sterilization process, and the initial load of microorganisms on the material being sterilized

Question 14

In what settings is steam sterilization commonly used?

Answer 14

Steam sterilization is commonly used in healthcare, food production, and laboratory work to ensure the safety and quality of materials and prevent the spread of infectious diseases.

Question 15

What is saturated steam sterilization?

Answer 15

Saturated steam sterilization is a method of sterilization that uses high-pressure, high-temperature steam to kill microorganisms.

Question 16

What is a log reduction value?

Answer 16

A log reduction value (LRV) is a measure of the effectiveness of a disinfection or sterilization process in reducing the number of microorganisms present on a surface or in a material.

Question 17

What is a D value in microbiology?

Answer 17

In microbiology, D value refers to the decimal reduction time, which is the amount of time it takes to reduce the number of microorganisms by one log or 90%.

Question 18

What is a Z value in microbiology?

Answer 18

In microbiology, Z value refers to the temperature change required to achieve a ten-fold change in D value.

Question 19

What are the types of saturated steam sterilisation cycles?

Answer 19

1. Aqueous Liquid
2. Non porous solids
3. Porous solids

Question 20

What is aqueous liquid?

Answer 20

Usually injected fluid or contact lens fluid. Not necassary for steam penetration.

Question 21

What is non porous solids?

Answer 21

Components sterilised at point of use such as hospital settings. Many medical devices are non porous solids such as scalpel. Moist heat is usually method of choice in labs. Critical that the items being sterilised as hermetically sealed into containers that are capable of:
1. Allowing steam to penetrate and come in contact with parts of product
2. Provide effective barriers to microbial ingress while still in tact.

Question 22

What is porous solids?

Answer 22

Sterile dressings, filters. Problematic to ensure steam contact with all parts of the porous materials because of entrapped air. Sterilising temperatures will not be achieved in presence of air.

Question 23

What are the key steps in sterilisation?

Answer 23

Preparation, loading, pre evacuation to remove sire prior to admission of steam, heat up, exposure, come down, drying.

Question 24

Preparation in sterilisation

Answer 24

Before sterilization, the item to be sterilized must be thoroughly cleaned to remove any dirt, debris, or other contaminants.The item to be sterilized must be properly prepared, such as by wrapping in sterilization packaging or placing in a sterilization container. All joint or rated surface instruments should be opened and placed in an unlocked position.

Question 25

Loading in sterilisation

Answer 25

Products placed and positioned carefully so steam or moist heat can be easily dispersed to reach all surfaces that need sterilisation. Instruments are not to be secured together tightly with rubber bands or clamps that might prevent contact with steam.

Question 26

Pre Evacuation air removal

Answer 26

Airs removed or displacement so steam heat effectively contact all surface and penetrates all areas to be sterilised

Question 27

Heat up/exposure

Answer 27

Heat up: time period when moist heat is brought to desired exposure temperature.
Heat up phase: microbial inactivation may begin @ < 105 degrees. Longer heat up reduces exposure time
Exposure: period of cycle in which microbes and products are in contact with saturated steam at set temp for certain time.

Question 28

Cool down

Answer 28

Period after exposure when pressure, temps and moisture are brought down to atmospheric conditions. Cooling reduces heat and eliminates moisture from steriliser. Microbial inactivation may continue above 105 degrees.

Question 29

Drying

Answer 29

Period following cool down where condensation is allowed to evaporate and hydrogen effects are reversed.

Question 30

What are the advantages of steam sterilisation?

Answer 30

1. It is relatively simple, compared to most chemical sterilisation methods.
2. There are no toxic residues or wastes.
   It requires minimal processing time.
3. The higher the temperature, the shorter the processing exposure time.
4. Steam is capable of destroying all viable forms of life, including prions.
5. Steam is generally the most dependable sterilant for laboratory use.

Question 31

What are the disadvantages of steam sterilisation?

Answer 31

1. To use and operate steam sterilisers and sterilisation properly requires special training in how to use the sterilisers and how to handle the items to be sterilised.
2. The steam must reach a suitable pressure for condensation to occur.
3. Boilers must be maintained and can corrode.
4. Anticorrosive steam additives can be toxic.
   5.The quality of the steam must be good; it must be condensable and free of non-condensable gases.

Question 32

What is EtO?

Answer 32

It is used as a sterilant for medical equipment and supplies. Unfortunately, EtO possesses several physical and health hazards that merit special attention. EtO is both flammable and highly reactive. Acute exposures to EtO gas may result in respiratory irritation and lung injury

Question 33

How does temperature affect the EO sterilization process?

Answer 33

Temperature can influence the rate of reaction between EO and microbial cells. Higher temperatures can increase the reaction rate, reducing exposure time required for sterilization. However, higher temperatures can also cause protein denaturation and cellular damage, decreasing the effectiveness of EO sterilization. EO sterilization is most effective at temperatures between 50-60°C with an exposure time of 2-4 hours. At higher temperatures, efficacy can decrease, and at lower temperatures, longer exposure times are required. It is crucial to carefully control temperature and exposure time during the EO sterilization process to ensure optimal results.

Question 34

What are the effects of gas concentration on microbial response to ethylene oxide (EO) sterilization?

Answer 34

The concentration of EO gas in the sterilization chamber plays a significant role in the efficacy of the EO sterilization process. Higher gas concentrations can reduce the exposure time required for sterilization by increasing the number of EO molecules available to react with microbial cells. However, higher gas concentrations can also increase the likelihood of residual toxicity and material damage.

Question 35

What are the effects of humidity on microbial response to ethylene oxide (EO) sterilization?

Answer 35

Humidity plays an important role in the effectiveness of EO sterilization. The presence of moisture can increase the rate of EO gas penetration into microbial cells, making the sterilization process more effective. However, excessive moisture can also reduce the efficacy of EO sterilization by interfering with the reaction between EO and microbial cells and by increasing the risk of material damage due to condensation.

Question 36

What is the internal construction of ethylene oxide sterilisers like?

Answer 36

The internal construction of ethylene oxide sterilisers is uncomplicated and uncluttered.

Question 37

Why is forced air circulation important in ethylene oxide sterilisers?

Answer 37

Forced air circulation is important in ethylene oxide sterilisers to prevent stratification of the various types of gas present in the chamber during sterilisation (sterilant, diluent, moisture).

Question 38

What devices should be present in ethylene oxide sterilisers for continuous monitoring and recording of temperature and pressure within the chamber?

Answer 38

There should be devices or sample ports for continuous monitoring and recording of temperature and pressure within the chamber of ethylene oxide sterilisers.

Question 39

What associated equipment may be present in ethylene oxide sterilisers to monitor gas concentration?

Answer 39

In some cases, associated equipment may be present in ethylene oxide sterilisers to monitor gas concentration.

Question 40

What safety measures must be taken when using electrical equipment in association with pure ethylene oxide sterilisers?

Answer 40

All electrical equipment used in association with pure ethylene oxide sterilisers must be spark-proofed/intrinsically safe.

Question 41

What is the purpose of the ancillary chamber in some ethylene oxide sterilisers?

Answer 41

In some instances, there may be an ancillary chamber in which the product load is equilibrated to a specified temperature and humidity prior to its introduction into the steriliser.

Question 42

What are the three intentions of pre-conditioning in ethylene oxide sterilisation?

Answer 42

The three intentions of pre-conditioning in ethylene oxide sterilisation are: (a) to equilibrate the microorganisms contaminating the product to conditions of temperature and water activity that are optimal for their inactivation by exposure to ethylene oxide, (b) to equilibrate the packaging to the conditions of the steriliser in order to prevent deleterious equilibria arising in the sterilisation chamber, and (c) to optimize the utilization of the steriliser.

Question 43

Why is preconditioning important in ethylene oxide sterilisation?

Answer 43

Preconditioning is important in ethylene oxide sterilisation because if it is not done elsewhere, it must be done in the steriliser, which would require a longer residence time of the product in the steriliser than necessary. Preconditioning chambers that do not operate under pressure are cheaper to build and operate than sterilisers.

Question 44

What are the advantages of Ethylene Oxide sterilisation?

Answer 44

1. Effectiveness and compatibility with most materials.
2. Can sterilize heat-, moisture- and/or radiation-sensitive medical items without deleterious effects on the material.
3. Sterilant of choice for many medical devices, especially thermolabile plastic, elastomer polymeric materials, electronic devices, and biomaterials.
4. Well-understood properties, allowing for quick development and validation of effective sterilisation processes.

Question 45

What are the disadvantages of Ethylene Oxide sterilisation?

Answer 45

1. Lengthy cycle, high cost, potential hazards to patients, staff, and environment, as well as risks associated with handling a flammable and explosive gas.
2. Requires properly designed area, sophisticated technology and equipment, feasible and ongoing engineering controls, safe work practices, and trained staff.
3. Requires additional degree of sterility assurance compared to steam processes, requiring more sterility test units or use of biological indicators.
4. Monitoring of sterilising parameters, barriers to gas penetration, and degree of microbial resistance is required.
5. Detectors are required to protect staff workers, as the gas is colorless and odorless until a level of 430 ppm, well above its toxic level.
6. Careful aeration of medical devices is required since absorbed Ethylene Oxide can leave toxic residues on/in them.

Question 46

What is the use of ionising radiation in sterilisation?

Answer 46

Ionising radiation is used extensively for terminal sterilisation of heat-sensitive medical devices and for heat-sensitive pharmaceutical packaging components prior to aseptic processing.

Question 47

What type of radiation is typically used in sterilisation by ionising radiation?

Answer 47

Gamma rays are typically used in sterilisation by ionising radiation.

Question 48

Besides gamma rays, what other type of radiation is sometimes used in sterilisation?

Answer 48

Accelerated electrons are sometimes used in sterilisation, but to a far lesser extent than gamma radiation.

Question 49

What are the advantages of gamma sterilisation processes?

Answer 49

Gamma sterilisation processes have excellent penetrative power and are easy to control.

Question 50

What is the main problem associated with handling of radioactive isotopes in gamma radiation sterilisation?

Answer 50

The main problem is the handling of radioactive waste.

Question 51

What are the four stages of the biological effects of ionizing radiation in matter?

Answer 51

The four stages are: (a) physical stage, (b) physicochemical stage, (c) chemical stage, and (d) biological stage.

Question 52

What happens in the physicochemical stage of the biological effects of ionizing radiation?

Answer 52

In the physicochemical stage, primary products react spontaneously or in collision with each other, bonds are broken, and highly reactive ions, radicals, and trapped charges are formed.

Question 53

What is the biological stage of the biological effects of ionizing radiation?

Answer 53

The biological stage is the series of biochemical reactions at different levels of cellular organization, giving rise to observable biological effects.

Question 54

What is the effect of oxygen on microorganisms during and after irradiation?

Answer 54

Microorganisms are more sensitive to radiation when oxygen is present during and after irradiation than in environments from which oxygen has been excluded.

Question 55

What is the first and most important property of gamma radiation as a robust process for industrial sterilization?

Answer 55

The first and most important property of gamma radiation as a robust process for industrial sterilization is its ability to penetrate matter with very high energy photons.

Question 56

What effect does the presence of oxygen have on microorganisms during radiation sterilization?

Answer 56

Microorganisms are more sensitive to radiation when oxygen is present during and after irradiation than in environments from which oxygen has been excluded. Oxygen sensitizes microorganisms to radiation, likely due to its reaction with free radicals formed by ionization of target molecules.

Question 57

What are gamma rays?

Answer 57

Gamma rays are photons of electromagnetic radiation that are very similar to x-rays. They are highly penetrative through matter and only lose energy when they collide with a nucleus, but they lose all their energy in one collision.

Question 58

How does the penetrative power of gamma radiation make it a robust process for industrial sterilization?

Answer 58

The penetrative power of gamma radiation allows it to pass through matter with the same energy as when it entered, just with fewer photons emerging. This property makes gamma radiation a robust process for industrial sterilization as it can penetrate barriers of varying thicknesses, ensuring thorough sterilization of heat-sensitive medical devices and pharmaceutical packaging components.

Question 59

What are the 7 elements of a gamma sterilisation plant?

Answer 59

1. Load/unload station/storage conveyor
2. Controls/safety systems
3. Source shield
4. Maze/interim conveyor
5. Source rack
6. Source pass conveyor and research loop
7. Source heist/ drivers

Question 60

Load/Unload Station/Storage Conveyor

Answer 60

Load/Unload Station/Storage Conveyor
Products in their final packaging, usually cardboard boxes, are loaded from shipping pallets into aluminum tote boxes at the load station. The totes are accumulated on a storage conveyor before entering the irradiator. The process is reversed at the unload station after the product has been irradiated.

Question 61

Controls/Safety Systems

Answer 61

A Programmable Logic Controller (PLC), control panel and computer are used to ensure the safe and efficient operation of the irradiator. Special safety systems and interlocks are designed to prevent anyone from entering the shield while product is being irradiated.

Question 62

Source Shield

Answer 62

A biological shield, constructed of high-density concrete approximately two meters thick, ensures that radiation is prevented from leaving the irradiator when the source rack is in the up position to irradiate product.

Question 63

Maze/Interim Conveyor

Answer 63

A specially designed maze allows totes to enter the shield, but does not allow radiation to escape. Conveyors and transfer mechanisms transport the totes through the maze to the source pass conveyor mechanism.

Question 64

Source Rack

Answer 64

Cobalt-60 sources are contained in a planar array which is stored in a deep pool of water when not in use. This provides shielding so that personnel may safely enter the shield to perform maintenance on the conveyor mechanism.

Question 65

Source Pass Conveyor& Research Loop

Answer 65

A precision conveyance mechanism indexes the totes around the source rack. For standard operation, the totes are moved through two passes on each side of the source rack, and two levels for each pass.
Other modes of operation allow the totes to complete one pass on each side of the source rack, or to make multiple ‘trips’ around the source rack.
A special overhead carrier may be used to test product or carry out small volume or precision irradiation without the need to interrupt regular production.

Question 66

Source Hoist/Drives

Answer 66

A pneumatic cylinder and source hoist mechanism are used to lift the source rack out of the pool for irradiating product.
If any fault occurs during the operation of the irradiator, the safety system will release the air pressure in the source hoist cylinder and the source rack will return to the safe position in the pool by force of gravity.
Electric drives and winches outside the shield are used to precisely control the movement of totes through cables and chains that pass through the shield.

Question 67

Advantages of Gamma Sterilisation

Answer 67

1. Compared with all other methods of sterilisation (hot or cold), gamma radiation has the overwhelming advantage of penetration through materials.
2. The advantages of penetration extend through all aspects of medical products, from initial design to the final presentation of the products in their shipping packs.

Question 68

Disadvantages of Gamma Sterilisation

Answer 68

1. The greatest disadvantage to gamma irradiation of plastic medical devices and pharmaceutical containers is the deleterious effects that radiation has on some polymers that might otherwise be preferred materials of manufacture.
2. From an end-use point of view, the most serious adverse effects of these interactions of radiation with polymeric materials are discoloration and weakened mechanical properties.
3. In medical devices markets, white and blue are perceived as “clean” colours, yellow and brown as “dirty” colours; radiation-induced discoloration in susceptible polymers ranges from slight yellowing to complete opacity.
4. The induction of brittleness and fragility in products intended to have strength and resilience are the most damaging effects of radiation on mechanical properties

Question 69

What can the electron beam process achieve?

Answer 69

The electron beam process can achieve widely differing effects, such as sterilisation, polymer modification, cross linking and chain scission, via its action as an ionizing radiation.

Question 70

What happens when a material is bombarded with high-energy electrons in the electron beam process?

Answer 70

The bombardment of a material with high-energy electrons results in a cascade of these electrons moving through the target material. These electrons are free to interact with molecules within the material, ejecting electrons from their orbits and generating free radicals.

Question 71

Which devices are routinely and terminally sterilized by electrons?

Answer 71

Devices such as surgical dressings, wound care products, electrocautery devices, IV administration kits, dialysers, endoscopy loops, cardiac catheters, and stents are routinely and terminally sterilized by electrons.

Question 72

How does the electron beam process achieve its effects?

Answer 72

The bombardment of a material with high-energy electrons results in a cascade of these electrons moving through the target material. These electrons interact with molecules within the material, generating free radicals that are responsible for the ability of the beam to induce breaks in the DNA double helix and prevent replication or expression of genes.

Question 73

What is the radiation source used in the electron beam process?

Answer 73

The process utilizes high-energy electrons as its radiation source. The electrons, which are produced by normal electrical current, are accelerated to near the speed of light by means of a linear accelerator.

Question 74

What is the energy range of the high-energy electrons used in the electron beam process?

Answer 74

The resulting energies, ranging normally from 3 to 10 million electron volts (MeV) and coupled with 1 to 50 kW of power, have sufficient energy to penetrate a range of materials.

Question 75

How does the electron beam process prevent radiation from leaving the cell?

Answer 75

The process takes place behind a thick concrete wall, which prevents radiation from leaving the cell.

Question 76

What are some of the medical devices that are routinely and terminally sterilized by the electron beam process?

Answer 76

Devices such as surgical dressings, wound care products, electrocautery devices, IV administration kits, dialysers, endoscopy loops, cardiac catheters, and stents are routinely and terminally sterilized by electrons.

Question 77

What are the main advantages of using electron beam technology for sterilization?

Answer 77

1. FDA approved, and recognized and accepted by international standards organizations
2. Allows control of temperature during irradiation
3. Causes no damage to sterile seals on product packaging
4. Reduced color change in any present polymers;
5. No chemical residuals remain on processed products – clean, safe, and environmentally friendly.

Question 78

How does electron beam sterilization compare to gamma sterilization?

Answer 78

1. The mechanism by which living organisms are destroyed is the same.
2. Both enjoy parametric/dosimetric release after processing.
3. Both utilize the same dosimetry and indicator systems
4. Both technologies are governed by the same ISO standards when applied to medical device sterilization—ISO 11137 and ISO 13409

Question 79

What is the difference between electron beam and gamma sterilization in terms of penetration?

Answer 79

1. Gamma rays can penetrate farther into materials, occasionally colliding with an electron and giving the affected electrons enough energy to destroy the bioburden. The gamma ray may then initiate more high energy electrons as it travels through the medical device.
2. Electron beams start out as very high energy electrons and destroy bioburden directly. In addition, these high energy electrons collide with other local electrons. These secondary electrons also have energy adequate to destroy bioburden.
3. This results in an increase in the dose required as the beam penetrates the medical device. Each succeeding collision reduces the energy of the resulting electrons until there is no penetrating power left in the beam.

Question 80

What is the difference between electron beam and gamma sterilization in terms of dose rate or processing time?

Answer 80

• The dose rate is the biggest difference between the two technologies. Gamma radiation has high penetration and low dose rate. E-beam has high dose rate and low penetration. Either technology can give a reproducible sterilization dose.
• Gamma radiation is best suited to treating a large batch of many “totes” of boxes over a six to ten hour cycle. E-beam is a continuous process that can deliver a required dose in one to two minutes as individual boxes pass by the e-beam accelerator.
• The lower “dwell time” in the E-beam irradiation process is less stressful to materials. The E-beam process allows faster turnaround time and more flexibility in delivering a specific irradiation dose to small batches of product. For example, e-beam can easily switch from decontaminating returned goods at 40 kGy to sterilizing a batch of radiation sensitive product at 15 kGy.

Question 81

What is the difference between electron beam and gamma sterilization in terms of their effects on materials?

Answer 81

• E-beam is less damaging to a plastic medical device and its packaging than gamma rays. This difference is attributed to the longer dwell time in gamma irradiation cells during which ozone, other reactive compounds, and heat can accumulate.
• The short dwell time of E-beam has less severe effects on materials because the radiation by-products rapidly dissipate after the short exposure to irradiation.

Question 82

What are the environmental considerations when comparing electron beam and gamma sterilization?

Answer 82

1. There are no direct environmental issues that affect the end users of contract sterilizer services.
2. The gamma irradiator must cope with higher containment and gamma ray source reprocessing costs, however, that may be reflected in overall operating costs.
3. With E-beam irradiation, when the power is turned off, the radiation stops