This document discusses sterilization and disinfection procedures. It begins with definitions of sterilization and disinfection. It then covers the historical perspective of sterilization practices. The Spaulding classification system for medical devices is introduced. The main methods of sterilization discussed are heat sterilization including steam sterilization and dry heat, along with radiation, hydrogen peroxide gas plasma, and chemical sterilization methods. Key steps in the sterilization process like cleaning, packaging, and loading are outlined. Monitoring of sterilization is also summarized.
3. DEFINITION
• STERILIZATION
– Process by which an article, surface or medium is
freed of all living micro organisms either in the
vegetative or spore state
• DISINFECTION
– Destruction or removal of all pathogenic
organisms, or organisms capable of giving rise to
infections
3
5. HISTORICAL PERSPECTIVE
• ANCIENT CIVILIZATION
-Used flame
• ARISTOTLE
– Advantage of Boiling of drinking water
• HIPPOCRATES
– Lightning fires to control plague
5
6. HISTORICAL PERSPECTIVE
• ROBORT KOCH
– usefulness of steam for sterilizing surgical
instruments and dressings (1878)
• CHARLES CHAMBERLAND (1851-1908)
6
7. HISTORICAL PERSPECTIVE
• GASTON POUPINEL 1885
– Dry heat sterilization
• Joseph Lister (1827-1912)
– A machine that pumped out a fine mist of carbolic
acid into the air around an operation
7
8. SPAULDING CLASSIFICATION
• Strategy for reprocessing contaminated
medical devices
• The system classifies a medical device as
– critical
– semi critical
– noncritical
8
9. SPAULDING CLASSIFICATION
CATEGORY DESCRIPTION REQUIREMENT EXAMPLE
CRITICAL Enters sterile body
cavity or vascular
system
Sterile Surg instrument,
cardiac catheters ,
implants
SEMI-CRITICAL Contacts mucous
membrane and non
intact skin
High level
disinfection
Endoscope,
bronchoscope,
Laryngeal mirror,
speculum
NON- CRITICAL Contacts intact skin Low level
disinfection
Bed pans, BP cuff,
bed rails
9
13. STEAM STERILIZATION (AUTOCLAVING)
Principle –
• Water boils when its vapour pressure equals that of
surrounding atmosphere.
• Thus when water is boiled in closed vessel at
increased pressure, the temperature at which it boils
& that of steam which is formed will exceed 100°C.
13
14. STEAM STERILIZATION (AUTOCLAVING)
• When steam comes in contact with cooler
surface, it condenses to water & gives up its
latent heat to that surface.
• Thus 1600ml of steam at 100°C & at
atmospheric pressure condenses into 1ml of
water at 100°C & releases 518calories of heat
14
15. • Air in Autoclave Chamber
– Air in the chamber will impair sterilization as it is
poor conductor of heat & retards the penetration
of steam.
– Efficacy of air removal process can be tested by
Bowie-Dick test.
15
17. STEAM STERILIZATION (AUTOCLAVING) ct..
• TYPES OF AUTOCLAVE STERILIZERS
– Downward Displacement
– Positive Pressure Displacement
– Negative pressure
– Super atmospheric cycles
– Sub atmospheric cycles
17
18. STEAM STERILIZATION (AUTOCLAVING)
ct..
Downward Displacement
• Also known as a gravity displacement unit.
• It uses a heating element to heat up the water and
produce steam.
• The steam, which is lighter than air, forces the air inside
the sterilization chamber to move downward.
• Eventually the air moves out through the drain hole of
the sterilization chamber.
18
20. STEAM STERILIZATION (AUTOCLAVING)
ct..
Positive Pressure Displacement
• It uses a separate chamber to create and hold steam.
• Once sufficient amount of steam is accumulated, it is
released into the sterilization unit in a pressurized blast
• This forces the air to move out through the drain hole
and starts the sterilization process.
20
22. STEAM STERILIZATION (AUTOCLAVING)
ct..
Super atmospheric cycles
– achieved with a vacuum pump
– It starts with a vacuum followed by a steam pulse
– The number of pulses depends on the particular
autoclave and cycle chosen.
22
23. STEAM STERILIZATION (AUTOCLAVING)
ct..
Sub atmospheric cycles
– similar to the super atmospheric cycles
– chamber pressure never exceeds atmospheric
pressure until they pressurize up to the sterilizing
temperature
23
25. STEAM STERILIZATION (AUTOCLAVING)
ct..
• PHASES OF AUTOLAVING
– Heat up Phase
• Air, if present, should be evacuated before sterilization
• Vacuum may be applied
– Sterilization phase
• Gives latent heat to materials rapidly on contact
• Microbial destruction will be most effective at these
locations
• Once intended temperature is reached, sterilization time is
set
25
26. STEAM STERILIZATION (AUTOCLAVING)
ct..
• PHASES OF AUTOLAVING
– Exhaust Phase-
• At the end the steam should be exhausted from the
autoclave to avoid condensation of water on the load
when cool air is admitted
26
27. STEAM STERILIZATION (AUTOCLAVING)
ct..
• Steam criteria
– Dry:
• no suspended droplets of water
– Close to its point of condensation:
• not superheated
– Free from air
27
29. STEAM STERILIZATION (AUTOCLAVING)
ct
• ADVANTAGES
– Can kill all bacteria, spores & viruses
– Rapid sterilization
– Ease of use
– Good penetration
– Economical
– Absence of toxic products/ residues.
– Materials can be pre-packaged & kept sterile until use
29
30. STEAM STERILIZATION (AUTOCLAVING)
ct..
• DISADVANTAGES
– Heat sensitive materials are damaged like plastic
& rubber goods.
– Cause blunting of cutting edges, crossing of metal
surfaces.
– Oil, grease, powders are not sterilized because of
lack of penetration.
– Shortened life of electronic components.
30
31. • Articles are packed in special craft papers and then
placed in a thermostatically controlled Dry Heat
Sterilizer.
• Mainly suitable for ophthalmic instruments and glass
items but not plastics or rubber.
• It is useful for sterilization of powders, grease, oil and
glass syringes.
• Precaution- temperature is raised and lowered slowly
to prevent breakage by uneven expansion.
DRY HEAT
31
36. • Manual cleaning
• For instruments which cannot be immersed in
water or machine washed
• orthopedic power drills & saws
• For instruments that are heat-sensitive
• laparoscopic & arthroscopic cameras
36
37. MECHANICAL CLEANING
• Instruments that are heat, moisture, and
pressure-sensitive should not be washed in
mechanical washers
• Examples: powered instruments, microsurgical
instruments, cameras
• Ultrasonic baths.
37
38. PACKAGING
• Once items are cleaned, dried, and inspected,
items are wrapped or placed in a rigid container
• Arranged in tray/basket according to guidelines
– Hinged instruments opened
– Items with removable parts should be disassembled
– Heavy items positioned not to damage delicate items
• Several choices to maintain sterility of
instruments: rigid containers, peel pouched;
sterilization wraps
38
39. Packaging
• An effective sterilization wrap would:
– Allow penetration of the sterilant
– Provide an effective barrier to microbial
penetration
– Maintain the sterility of the processed item after
sterilization
– Puncture resistant and flexible
• Multiple layers are still common practice due
to the rigors of handling
39
41. LOADING
– Arranged so all surfaces will be directly exposed to
the sterilizing agent
– Allow for proper sterilant circulation;
– Perforated trays should be placed so the tray is
parallel to the shelf
– Small items should be loosely placed in wire
baskets
– Peel packs should be placed on edge in perforated
or mesh bottom racks or baskets
41
42. STERILIZATION MONITARING
• Sterilization monitored routinely by combination of
physical, chemical, and biological parameters
• Physical - cycle time, temperature, pressure
• Chemical - heat or chemical sensitive inks that
change color when germicidal-related parameters
present (Class 1-6)
• Biological - Bacillus spores that directly measure
sterilization
42
43. MONITORING
• Mechanical Monitors: Devices that record time,
temperature & pressure.
• Biological Indicators: they are standardized
preparation of spores. A positive biological indicator
is indicative of possible sterilization process failure.
They should be used at least once a week but time
needed for incubation is long. Eg: spores of Bacillus
Stearothermophilus
43
44. BIOLOGICAL MONITORS
• Steam - Bacillus stearothermophilus
• Dry heat - B. subtilis
• ETO - B. atrophaeus
• New low temperature sterilization
technologies
HP gas plasma - B. stearothermophilus
Ozone-B. stearothermophilus
44
46. • Class 1- These are Internal & External Process
Indicator E.g. External Process Indicator –
Autoclave Tape.
46
47. • Class 2- E.g. Bowie-Dick test for vacuum
steam sterilizer. They only assess Vacuum
Pump efficiency & detect the presence of air
leaks &/or gases in steam.
47
48. • Class 3 -
E.g. Temperature Tube. Contains chemicals that
melts & sometimes changes color when the
appropriate temp is attained.
• Class 4 -
Respond to one or more sterilization parameters.
Contains Ink that changes color when exposed to
correct combination of sterilization parameters.
48
49. • Class 5-
Known as Integrating Indicators. Respond to all
parameters of sterilization over a specified range of
temperatures.
• Class 6-
These are emulating indicators. These are designed
to react to all critical parameters over a specified
range of sterilization cycles for which the stated
values are based on the settings of the selected
sterilization cycles
54. Non- Ionising radiation
• Eg: UV rays, IR rays
• Electromagnetic rays with wavelength longer than light
• Low energy type
• Absorbed as heat
• Used in rapid mass sterilisation of prepacked syringes
and catheters
• Used for disinfecting enclosed areas like entryways,
operation theatres and laboratories.
54
55. Ionising radiation:
• Eg; X- rays, gamma rays & cosmic rays
• Highly lethal to DNA
• High penetrative power
• High energy type
• No appreciable increase in the temperature – COLD
STERILISATION
• To sterilize plastics, syringes,catheters, swabs.
55
56. HYDROGEN PEROXIDE GAS PLASMA
STERILIZATION
• Plasma is ionized gas made up of ions and electrons
referred to as fourth state of matter
•Plasma sterilization operates synergistically via three
mechanisms:
– Free radicals interactions
– UV radioactive effects
– Volatilization
56
57. • Stage I- vacuum or pre plasma state
• Low air pressure is achieved and low temperature air
plasma is generated
• Helps remove residual moisture of chamber
• Stage II- sterilization stage
• Aqueous solution of H2O2 injected and vaporised
• Diffuses throughout the chamber, surrounds the items
to be sterilized
• Inactivation of microorganisms by free radicals
generated in plasma by breaking apart H2O2 vapours
57
58. Advantages
• Safe for the environment and staff; it leaves no toxic
residuals(water and oxygen).
• Fast - cycle time is 35-40 min and no aeration
necessary
• Used for heat (process temperature 50oC) and
moisture sensitive items.
• Simple to operate, install, and monitor.
• Rubber, plastics,laparoscopic
instruments,ureteroscope, cystoscope,
bronchoscope,electronic power devices
58
59. Disadvantages
• Paper, linens and liquids cannot be processed
• Sterilization chamber is small (volume- 80L)
• Requires synthetic packaging (polypropylene) and
special container tray
59
61. OTHER STERILIZATION METHODS
• Ozone –
- Sterilises by oxidation
- highly reactive
- high concentration required to produce sporicidal
effects
-Conc: 6-12%. Contact time-60min.
Disadvantage-
- Corrosive when used at high concentrations
61
62. TYPES OF DISINFECTION
• High-level disinfection
- Destroy all microorganisms
- Large numbers of bacterial including spores
- Eg: Gluteraldehyde, H2O2
• Intermediate disinfection
- Inactivates Mycobacterium tuberculosis
- Vegetative bacteria, most viruses, and most fungi
- Does not kill spores
- Eg : Alcohol, Phenol, Iodine
• Low-level disinfection
- Kills only vegetative bacteria
- Fungi and lipid enveloped viruses
- Eg: Quarternary ammonium compound
63. RADIATION DISINFECTION
• High energy ionizing radiation destroys
microorganisms and is used to sterilize pre packed,
single-use, surgical equipment by manufacturers
• Common sources of radiation include electron beam
and Cobalt-60
• Disadvantage:
Penetrates human tissues. May cause genetic
mutations in humans.Industrial large scale setup
64. SATISFACTORY CRITERIA OF CHEMICAL METHODS
1. Active against wide range of organisms and spores
2. Non-corrosive
3. Non-irritant
4. Economical
5. Penetrate grease & fibers
6. Non-toxic
7. Persistent
65. FACTORS INFLUICING CHEMICAL DISINFECTION
a) Concentration of the Chemical
• Rate of kill of bacteria varies with the concentration of
the disinfectant.
b) Temperature
• Designed to be used at room temperature.
c) Evaporation and light deactivation
• Volatile agents evaporate easily. Exp: Chlorine Products.
Exposure to light adversely affects the disinfectant.
66. d) PH
• Alcohols work best in alkaline PH
• Aldehydes work best in acidic PH
e) Bioburden
• Effectiveness depends on the nature and number of
microorganisms
f) Characteristics of the item to be sterilized:
• Disinfectant will be effective, if it can contact all the
surfaces on the item
67. g) Time
• Different chemical agents to function effectively varies
from seconds to hours.
h) Use Pattern, Use Life & Storage Life
• How many times the solution can be used
• Limited period of time during which activated solution
can be used
• Time period after which the unused or inactivated
product is no longer effective.
68. GLUTRALDEHYDE
• Saturated di aldehyde
• High-level disinfectant and chemical sterilant
• Aqueous solutions of glutaraldehyde are acidic
• Solution is “activated” (made alkaline) by use of
alkalinating agents to pH 7.5–8.5
• Shelf-life of minimally 14 days
• Mechanism of action
– Denaturation of proteins
– Alkylation of nucleic acid
70. Advantages Disadvantages
• Relatively inexpensive
• Easy availability
• Excellent materials
compatibility
•It kills spores within 12
hrs and viruses within
10 min
• Respiratory irritation
• Pungent and irritating odor
• Relatively slow
mycobactericidal activity
• Coagulates blood and fixes
tissue to surfaces
• Allergic contact dermatitis
71. PER ACETIC ACID
• Mixture of hydrogen peroxide and acetic acid
• Highly Biocidal oxidizer that maintains its efficacy in
the presence of organic soil.
72. • Mechanism of action
– Denatures proteins, disrupts cell wall permeability
– Inactivate gram-positive and gram-negative
bacteria, fungi, and yeasts in <5 minutes
73. Advantage Disadvantage
• No activation require
• Less irritation
• Materials compatibility
concerns (lead, brass,
copper, zinc)
• Potential for eye and skin
damage
74. HYDROGEN PEROXIDE
Advantage Disadvantage
•No activation required
•Remove the organic matter,
organism
• No odor or irritation issues
• Does not coagulate blood or fix
tissues to surfaces
• Inactivates Cryptosporidium
•Material
compatibility concerns
(brass, zinc, copper,
and nickel/silver
plating) both cosmetic
and functional
• Serious eye damage
75. ORTHO-PTHALALDEHYDE
Advantage Disadvantage
• Fast acting
• No activation required
• Odour not significant
• Excellent materials
compatibility
• Does not coagulate blood or fix
tissues to surfaces
•Stains skin, mucous
membranes, clothing,
and environmental
surfaces.
•Hypersensitivity rxn
• More expensive than
glutaraldehyde
• Eye irritation
• Slow sporicidal
activity
76. ALCOHOL
• Intermediate level disinfectants
• 60-90 % Concentration Ethyl alcohol is bactericidal
• Kill the bacteria but not spores, action against viruses is
variable.
• Exposure to 70% ethanol for 15mins to inactivate the
hepatitis virus but 1 min for HIV.
• Effectiveness is limited because of rapid evaporation, lack
of ability to penetrate organic matter.
• Used to disinfect external surfaces of equipment
like stethoscopes, ventilators, fiberoptic cables
77. CHLORHEXIDINE (SAVLON)
• Non detergent chemical disinfectant
• Usually used in the concentration of 0.5%
in 70% alcohol for skin.
• Tubes, masks are sterilized by keeping for
20 min in 0.1% aqueous solution.
78. CHLORINE AND CHLORINE PRODUCTS
• Intermediate level disinfectants.
• Active against bacteria and viruses but not spores
• Available both in liquid (sodium hypochlorite) and solid
(Calcium hypochlorite) forms.
• Widely used, inexpensive and fast acting.
• Household bleach is an inexpensive and excellent source
of sodium hypochlorite.
• 1:100 to 1:1000 dilution is effective against HIV
• 1:5 to 1:10 dilution is effective against hepatitis
79. • Use is limited by their corrosiveness, inactivation by
organic matter
• Residue of which causes irritation to skin, eye and
respiratory tract
• Potential hazard is the production of carcinogen bis-
chloromethyl ether, when hypochlorite solutions
come into contact with formaldehyde.
• A mixture of hypochlorite with acid will cause rapid
evolution of toxic chlorine gas.
80. • Cidex is a common designation for variety of
solutions with antimicrobial or disinfection purpose
• Cidex OPA- with ortho-phthalaldehyde
• Acitivity against mycobacterium
• Requires no activation
• Minimal odour
• Nu-Cidex- with peracetic acid
• Cidex plus- with gluteraldehyde
81. Sl no Name Concentration
1 Gluteraldehyde 2%
2 Phenol 5%
3 Sodium hypochlorite 0.5-5%
4 Chlorhexidine 1-4%
5 Poviodine iodine 10%
6 Alcohol 70-80%
COMMONLY USED CONC OF DISINFECTANTS
82. GASEOUS STERILISATION
Ethylene oxide
• Colorless gas, available as cartridges
• Toxic and flammable, Odor similar to ether
• Has an extremely well penetration, even through
plastics
• Powerful sterilizer: Kills all known viruses, bacteria
(including spores), and fungi
83. ETHYLINE OXIDE
• Advantages
– Effective at killing microorganisms
– Penetrates medical packaging and many plastics
– Compatible with most medical materials
• Disadvantages
– Potential hazard to patients and staff
– Lengthy cycle/aeration time
84.
85. GASEOUS CHLORINE DIOXIDE
- Short lived highly reactive oxidizing gas disrupts
proteins
- Interferes with membrane transport and protein
synthesis
- Decontamination contact time- 6hrs
- Presence of organic matter reduces activity
86. FUMIGATION
• Gaseous sterilization
• Completely fills the area with gaseous fumigants
• Kills the microorganism and prevent the growth of
microorganism in air, surface, floor
• Used in Operation theatrs,Hospital,Pharmaceuticals
88. FORMALDEHYDE GAS
• seal windows and doors
• Gas is generated by adding 150mg of KMnO4 to
280ml of formalin for every 1000 cu ft of room
volume
• Room left un open for 48hrs
89. Advantage-
– inexpensive and easy to handle
– Broad spectrum efficacy
– Effective against M. tuberculosis
Disadvantage:-
– Slow acting, time consuming and poor penetration
– Toxic and carcinogenic
90. COMMONLY USED METHODS
Sr
no
Name of article Method
1 Surgical linen Autoclaving
2 Syringes , needles,
catheters, gloves
Gamma radiations
or ethylene oxide
3 Culture media Autoclaving
4 Glassware, paraffin, glove
powder, jellies
Hot-air oven
5 Sthethoscope, probes,
thermometer
alcohol
91. STORAGE OF STERILE ITEMS
• Storage area should be well-ventilated ,
provides protection against dust, moisture,
and temperature and humidity extremes.
• Sterile items should be stored so that
packaging is not compromised
• Items should be labeled with a load number
that indicates the sterilizer used, the cycle or
load number, the date of sterilization, and the
expiration date.
