STERILIZATION

1. STERILIZATI
ON

2. CONTENTS
• Introduction
• Physical Sterilization
• Chemical Sterilization
• Mechanical Sterilization
• Conclusion
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3. INTRODUCTION
• Sterilization refers to any process that removes, kills, or deactivates all forms of life and
other biological agents like prions present in a specific surface, object or fluid, for example
food or biological culture media. Sterilization can be achieved through various means,
including heat, chemicals, irradiation, high pressure, and filtration.
• Sterilization is distinct from disinfection, sanitization, and pasteurization, in that those
methods reduce rather than eliminate all forms of life and biological agents present. After
sterilization, an object is referred to as being sterile or aseptic.
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4. 4
Sterilization
Physical
Dry heat
Red
heat
Flaming
Incinerat
ion
Hot Air
Oven
Moist
heat
Below
100°C
•Vaccine
Bath
•Pasteurizati
on
•Fractional-
Sterilization
At 100°C
Boiling
Tyndallizati
on
Above
100°C
Autoclav
e
Radiatio
n
Ionizing
Radiation
Non-Ionizing
Radiation
Chemical
Disinfectant
s
Antiseptics
Mechanical
Filteration
METHOD of
STERILIZATION

5. PHYSICAL STERILIZATION
 Dry heat
• Simplest method is exposing the item to be sterilized to the naked flame e.g. Bunsen burner-
for sterilizing bacteriological loops, knives, blades.
• Heat sterilization is the most widely used and reliable method of sterilization, involving
destruction of enzymes and other essential cell constituents.
• It employs higher temperatures in the range of 160-180°C and requires exposures time up to 2
hours, depending upon the temperature employed.
• The benefit of dry heat includes good penetrability and non-corrosive nature which makes it
applicable for sterilizing glass-wares and metal surgical instruments.
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6. PHYSICAL STERILIZATION
• It is also used for sterilizing non-aqueous thermo-stable liquids and thermostable powders.
• Dry heat destroys bacterial endotoxins (or pyrogens) which are difficult to eliminate by other
means and this property makes it applicable for sterilizing glass bottles which are to be filled
aseptically.
• Examples of Dry heat sterilization are:-
 Incineration
 Red heat
 Flaming
 Hot air oven
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7. 7
Incineratorat
or
Red Heat
Hot Air
Oven
Flamin
g
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8. Pros & Cons of Dry heat Sterilization
• A dry heat cabinet is easy to install and has relatively low operating costs.
• It penetrates materials & It is nontoxic and does not harm the environment.
• It is noncorrosive for metal and sharp instruments.
• Time consuming method because of slow rate of heat penetration and microbial killing.
• High temperatures are not suitable for most materials.
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9. PHYSICAL STERILIZATION
 Moist Heat
o Moist heat kills microorganisms by denaturing proteins.
o Moist heat may be used in three forms to achieve microbial inactivation.
Dry saturated steam – Autoclaving
Boiling water/ steam at atmospheric pressure
Hot water below boiling point
Pasteurisation
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10. PHYSICAL
STERILIZATION
• Moist heat sterilization involves the use of steam
in the range of 121-134°C.
• Steam under pressure is used to generate high
temperature needed for sterilization.
• Saturated steam acts as an effective sterilizing
agent.
• Steam for sterilization can be either wet
saturated steam or dry saturated steam.
 Pasteurization
o Pasteurization is the process of heating the milk
at a temperature of 60 degrees or 72 degrees 3
to four times.
o Here alternative heating and cooling kills all the
microbes and molds without boiling the milk.
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11. PHYSICAL
STERILIZATION
Boiling
o quite common especially in
domestic circumstances.
o Boiling is done for metallic
devices like surgical
scissors, scalpels, needles
etc. like instruments. Here
substances are boiled to
sterilize them.
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12. PHYSICAL
STERILIZATION
 Autoclave
o Standard sterilization method in hospitals.
o The Autoclave works under the same principle as
the pressure cooker where water boils at
increased atmospheric pressure i.e. because of
increased pressure the boiling point of water is
>100°C.
o The autoclave is a tough double walled chamber
in which air is replaced by pure saturated steam
under pressure.
o Before using the autoclave, check the drain
screen at the bottom of the chamber and clean if
blocked. If the sieve is blocked with debris, a
layer of air may form at the bottom of the
autoclave, preventing efficient.
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13. PHYSICAL
STERILIZATION
o The air in the chamber is flushed out and filled with saturated
steam. Water is boiled to produce steam, which is released
through the jacket and into the autoclave's chamber. Hot,
saturated steam enters the chamber and the desired
temperature and pressure, usually 121°C.
o At this temperature saturated steam destroys all vegetative cells
and endospores. Moist heat is thought to kill so effectively by
degrading nucleic acids and by denaturing enzymes and other
essential proteins. It also may disrupt cell membranes.
o The chamber is closed tightly the steam keeps on filling into it
and the pressure gradually increases. The items to be sterilized
get completely surrounded by saturated steam (moist heat)
which on contact with the surface of material to be sterilized
condenses to release its latent heat of condensation which adds
to already raised temperature of steam so that eventually all the
microorganisms in what ever form are killed.
o The usual temperature achieved is 121 °C at a pressure of 15
lbs.ie. at exposure time of only 15-20 mins. By increasing the
temperature, the time for sterilizing is further reduced.
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14. PHYSICAL
STERILIZATION
Radiation
oIt is the energy in the form of waves or
particles. Two types of radiation are used:-
Ionizing radiation
oMore effective than UV rays.
oExamples :- X- rays, γ- rays
Non- ionizing radiation
oIt includes UV light & infrared
oSuitable for transparent fluids & surfaces of
objects.
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15. CHEMICAL STERILIZATION
• Useful for heat sensitive materials e.g. plastics and lensed instruments endoscopes.
• The sterilizing agent must be stable upon storage, odorless or with a pleasant odor, soluble in
water and lipids for penetration into microorganisms, and have a low surface tension so that it
can enter cracks in surfaces.
 Disinfection
o A substance of Chemical nature used for destroying or removing pathogenic microorganisms is
known as disinfectants & the process is called disinfection.
o This method kills only vegetative form & not spores.
o These are mainly use on non-living objects like working surface, table, desk, etc.
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16. Chemical
Sterilization
Formaldehyde
It is a gaseous disinfectant. It is used for woolen blankets,
hospital wards, operation theatre, etc.
The articles or rooms are exposed to formaldehyde gas
for four hours.
Halogens
These are bactericidal substances & effective on spores
also. Example Chlorine is used in water & iodine is used on
skin.
Chloroform
It kills the vegetative bacteria & can also be used to
preserve the serum. 16
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17. CHEMICAL STERILIZATION
 Antiseptics
 These chemicals prevents the infections by inhibiting the growth of microorganisms. They are
mainly used on living tissues such as skin.
 Acriflavin
 1:1000 dilution is used for treating wound & is effective against gram positive bacteria.
 Cetrimide
 1% solution is used as antiseptic.
 It is used for cleansing skin, wound, & sterilizing surgical equipments.
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18. MECHANICAL STERILIZATION
 Filteration
 Does not destroy but removes the microorganisms Used for clarification and sterilization of
liquids and gases.
 The major mechanisms of filtration are Sieving, Adsorption and Trapping within the matrix of
the filter material Ex: HEPA FILTERS.
 Used in the treatment of heat sensitive injections & ophthalmic solutions, biological pdts & air &
other gases for supply to aseptic areas.
 Used in industry as part of the venting systems on fermentors, centrifuges, autoclaves and
freeze driers. Membrane filters are used for sterility testing
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19. CONCLUSION
• As we have seen the new methods used in sterilization, which have been developed in
the past few decades and currently in use in the industries for sterilizing medical
instruments.
• Most of these methods are automated and efficient, environment friendly, have low
running cost, can sterilize on a large scale, highly effective against certain resistant
microorganisms and ensure complete sterility of products.
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20. REFERENCES
• webuserblog.com
• microbeonline.com
• pharmawiki.in
• microbenotes.com
• medicallabscientist.org
• Biologydiscussion.com
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