2. STERILIZATION – is the process by
which all living micro-organisms both
pathogenic and non-pathogenic
including spores are killed.
3. • prevention of surgical site infection in
health care areas is largely dependent on
aseptic techniques by all personnel who
performs any invasive procedure
– Patients
– items directly used in such procedures
– disinfections of all surfaces and other items in
the immediate environment.
4. • Surgical instruments, linen and heat
sensitive items sterilized by method
recommended by manufacturer
• No disposable items designed for
sterile single use should be
processed.
5. METHODS OF
STERILIZATION:
It is essential for a sterilizing
agent to be in contact with every
surface of each item or device to
be sterilized for specified period
of time at specified temperature.
6. A. Physical Methods:
Heat –safest and surest method of
sterilization
– dry (hot air ovens, flaming, incineration)
– moist (pasteurization, boiling,
autoclave).
7. • Dry heat,
– Hot air ovens –electrically heated and
usually with an internal fan to provide even
distribution of heat
– Sterilizing time -one hour at 160ºC
– suitable for ophthalmic instruments,
glassware and sealed jars.
8. • Sterilisation control: spores of nontoxigenic strain of
C. tetani
• Paper strips impregnated with 10 6 spores placed in
envelopes and inserted into suitable packs
• After sterilisation, strips are removed and
inoculated into thioglycollate or cooked meat media
and incubated for sterility test under strict anaerobic
conditions for 5 days at 37 °C.
• Browne's tube (green spot) –After proper
sterilisation green colour produced (after 60
minutes at 160 °C or 115 minutes at 150 °C).
• Thermocouples may also be used periodically.
9. • Flaming: Inoculating loop or wire, tip of forceps
held in bunsen flame till become red hot.
• Incineration: excellent method for safely
destroying contaminated cloth, animal
carcasses, pathological materials.
11. Temperatures below 100 °C
• Pasteurisation: milk heated at either 63 °C for 30
min (holder method) or 72 °C for 15-20 sec (flash
process) followed by cooling quickly to 13 °C or
lower
• all nonsporing pathogens(mycobacteria, brucellae
and salmonellae) destroyed
• Coxiella burnetli is relatively heat resistant and
may survive holder method.
12. Inspissation
• Media Lowenstein—Jensen and Loeffler's
serum are rendered sterile by heating at
80-85 °C for 30min on three successive
days in an inspissator
13. Temperature at 100 °C
• Boiling: Vegetative bacteria are killed at 90-100 °C, but
sporing bacteria require prolonged periods of boiling
• Boiling is not recommended for sterilising of
instruments used for surgical procedures and should
be regarded only as a means of disinfection.
14. Steam at atmospheric pressure
(100°C)
• Tyndallisation or intermittent sterilisation:
– An atmosphere of free steam is used to sterilize
culture media which may decompose if subjected to
higher temperatures
• Koch or Arnold steamer
• Single exposure of 90 min usually ensures sterilisation
but for media containing sugars or gelatin, 100 °C for 20
min on 3 successive days
15. Moist heat, at raised atmospheric
pressure
• Steam autoclave (steam under pressure)
• most inexpensive and effective method of
sterilization
• Principle: water boils when its vapour pressure equals
that of surrounding atmosphere
• when pressure inside closed vessel increases, temp.
at which water boils also increases
• Saturated steam has penetrative power. When steam
comes into contact with cooler surface it condenses to
water and gives up its latent heat to that surface
• usual method of sterilizing surgical instruments,
dressing, drapes, swabs, laps sponges and culture
media.
16. WHAT IS AN AUTOCLAVE?
• Closed chamber in which items or objects are
subjected to steam at high pressures, temperatures
above 100ºC
• Steam is more efficient method of sterilization than air
at the same temperature
• If air is present in sterilizing chamber, satisfactory
temperature will not be achieved
• pockets of air may prevent penetration of load of
articles by steam
• air must therefore be removed.
17. TYPES OF AUTOCLAVES
• DOWNWARD DISPLACEMENT AUTOCLAVES
– Air is removed in two stages and sterilization is effected by an
atmosphere of pure steam.
• The minimum exposure time is required for sterilizing
instruments is 50 min at 131ºC or 60 min at 136ºC.
• Bulky dressings, surgical swabs and surgical drapes
require exposures two or three times as long.
•
18.
19. • HIGH VACCUM / HIGH PRESSURE AUTOCLAVE
– Air is removed by powerful pump
– Steam penetrate load instantaneously and very rapid
– sterilization of dressings, instruments, raytec swabs, lap
sponges and packs is possible in 15 to 30 minutes at 134ºC.
20.
21. • Sterilisation control:
• spores of Bacillus stearothermophilus
• This is a thermophilic organism with optimum growth
temp. of 55-60 °C and its spores require an exposure of
12 minutes at 121 °C to be killed.
22. Method Temperature (°C) Holding time (in
minutes)
Autoclave 121 15
126 10
134 3
Hot air oven 160 45
170 18
180 7.5
190 1.5
23. Causes of failure
Faults in autoclave and the way it is operated
It maybe:
– Poor quality steam
– Failure to remove air and condensate
– Faulty gauges and timings
– Leaking door seals
26. MAKING OF STERILE PACKAGES
• Autoclave tapes should be visible on outside of every
package sterilized
• Autoclave tape is designed black when a certain
temperature inside the autoclave is reached. This is
usually at 120ºC to 135ºC depending upon the length
of the selected time cycle.
• Every package, tray or item is to be labeled with the
processing date, autoclave used and load number.
This will assist locating processed items in case of
recall.
27. PREPARATION OF ITEM
BEFORE STERILIZATION
1. Decontamination
2. Disassembly
3. Washing
4. Drying
5. Packing
6. Loading in sterilizer
31. • Sterile packages must be stored and
issued in correct order.
• Sterile items are good for either 30
days or 6 months depending solely on
how the packages are wrapped and
what type of wrappers are used. This is
called the shelf life which refers to the
length of time a package maybe
considered sterile.
32. • The storage room must be
subjected to adequate pest
control to prevent contamination
from rodents, ants and
cockroaches.
• Traffic is restricted to CSSD
personnel and trainees only.
33. FILTRATION
• Helps to remove bacteria from heat labile liquids-sera
and solutions of sugars or antibiotics used for preparation
of culture media
• Candle filters:
– two types
• Unglazed ceramic filters (for example,
Chamberland and Doulton filter
• Diatomaceous earth filters(for example, Berkefeld
and Mandler filters).
• for purification of water for industrial and drinking
purposes
34. • Asbestos filters: disposable, single-use discs
– Seitz and Sterimat filters
• Sintered glass filters
• Membrane filters: made of cellulose esters Or
other polymers
– Water purification and analysis, sterilisation and
sterility testing, preparation of solutions for
parenteral use.
– Wide range of average pore diameters (APD),
0.22 mm size being
– most widely used for sterilisation.
35. RADIATION
• Nonionising radiation
– Infrared radiation: used for rapid mass sterilisation of
prepacked items, syringes and catheters
– Ultraviolet radiation: used for disinfecting enclosed areas,
operation theatres and laboratories.
• Ionising radiation: X-rays, gamma rays and cosmic rays
– Cold sterilisation
– Gamma radiation for plastics, syringes, swabs, catheters,
animal feeds, cardboard, oils, greases, fabrics and metal foils.
36. CHEMICAL AGENTS
• Modes of action:
– protein coagulation
– disruption of cell membrane resulting in exposure,
damage or loss of contents
– removal of free sulphydryl groups essential for
functioning of enzymes
37. ALCOHOLS
• Ethyl alcohol (ethanol) and isopropyl alcohol
• Skin antiseptics, act by denaturing bacterial proteins
• 60-90% conc.
ALDEHYDES:
• Formaldehyde- 10 % formalin containing 0. 5%
sodium tetraborate
• used for sterilising instruments, heat sensitive
catheters, fumigating wards, sick rooms,laboratories.
• Irritant vapour nullified by exposure to ammonia
vapour after disinfection
38. Glutaraldehyde:
• effective against tubercle bacilli, fungi, viruses
• less toxic and irritant to eyes and skin
• used to treat corrugated rubber anesthetic tubes, face
masks, plastic endotracheal tubes, metal instruments,
polythene tubing.
• DYES: aniline dyes & acridine dyes used extensively as
skin and wound antiseptics
• HALOGENS: Iodine in aqueous and alcoholic solution
widely used as skin disinfectant
• Actively bactericidal, with moderate action against
spores.
• It is active against the tubercle bacteria and viruses.
39. PHENOLS
• Cause cell membrane damage, releasing cell contents
and causing lysis
• Lysol, cresol, Hexachlorophene, Chlorhexidine
• GASES:
• Ethylene Oxide (EO) – for sterilizing heat labile articles.
• Colorless at ordinary temperatures, odor similar to that
of ether and inhalation toxicity similar to that of
ammonia dioxide or fluorinated hydrocarbons (FREON).
• highly inflammable and concentrations in air greater
than 3%, highly explosive
40. • action is due to alkylating amino, carboxyl, hydroxyl and
sulphydryl groups in protein molecules
• effective against all types of microorganisms including
viruses and spores
• specially used for sterilising heart—lung machines,
respirators, sutures, dental equipment, books, clothing
41. • Before EO sterilization, objects also need to be
cleaned thoroughly and wrapped in a material
that allows the gas to penetrate.
• indicators for EO should be used with each
package to show that it has been exposed to gas
sterilization process.
• usually Bacillus Atropheus formerly BACILLUS
SUBTILIS VAR. NIGER.
• exposure period of 3 to 7 hrs is necessary for
complete sterilization.
42. ADVANTAGES OF EO:
• EO sterilization should be used only if materials are
heat sensitive and unable to withstand sterilization
by saturated steam under pressure.
• EO is easily available and is effective against all
types of microorganisms.
• EO easily penetrates through masses of dry
materials; does not require high temperatures,
humidity or pressures.
• EO is non- corrosive and non- damaging to items.
43. DISADVANTAGES OF EO:
• EO sterilization is expensive and more complex
process.
• Liquid EO may produce serious burns on exposed
skin if not immediately removed.
• It is toxic and can cause Cancer. Precautions
should be taken to protect personnel.
44. Formaldehyde gas
• For fumigation of OT and rooms
• formaldehyde gas is generated by adding 150 g of
ΚMnO4 to 280 ml formalin
• reaction produces considerable heat, and so heat
resistant vessels should be used
• After starting generation of formaldehyde vapour,
doors should be sealed and left unopened for 48
hours.
45. SURFACE ACTIVE AGENTS
• anionic, cationic, nonionic, amphoteric.
• most important antibacterial agents are cationic
surface active agents
• act on phosphate groups of cell membrane
membrane loses its semipermeability and cell
proteins denatured
• quaternary ammonium compounds:bactericidal,
active against Gm +ve organisms, lesser extent on
GN
• no action on spores, tubercle bacilli and most
viruses
• acetyl trimethyl ammonium bromide (Cetavlon or
cetrimide) and benzalkonium chloride.
