Sterilization techniques .TYPES .MERTIES. AND DIMERTIES AND APPLICATION......

STERILIZATION
TECHNIQUES
s.palaniananth
microbiology
B.Sc biotechnology III RD YEAR
Alpha arts and science college

CONTENT
 WHAT IS STERILZATION ?
 METHODS OF STERILIZATION
 IMPORTANCE OF STERILIZATION
 ADVANTAGES AND
DISADVANTAGES
 WHY NEEF OF STERILIZATION

WHAT IS STERILZATION ?
Sterilization can be defined as any
process that effectively kills or eliminates
transmissible agents (such as fungi, bacteria,
viruses and prions) from a surface, equipment,
foods, medications, or biological culture
medium

METHODS OF STERILZATION
The various methods of sterilization are:
1. Physical Method
 Thermal (Heat) methods
 Radiation method
 Filtration method
2. Chemical Method
• Gaseous method

PHYSICAL METHODS:
 HEAT STERILIZATION: Heat sterilization is the
most widely used and reliable method of
sterilization, involving destruction of enzymes
and other essential cell constituents.
 This method of sterilization can be applied
only to the THERMO STABLE PRODUCTS, but
it can be used for MOISTURE-SENSITIVE
MATERIALS.
 i) Dry Heat (160-1800˚C) Sterilization for
thermo stable products
 ii) moist heat (121-1340 ˚C) sterilization is
used for moisture- resistant materials.

 The efficiency with which heat is able to
inactivate microorganisms is dependent upon
i) the degree of heat, the exposure time and
ii) the presence of water.
 The action of heat will be due to induction of
lethal chemical events mediated through the
action of water and oxygen.
 In the presence of water much lower
temperature time exposures are required to
kill microbe than in the absence of water.

THERMAL (HEAT) METHODS
Thermal methods includes:
Dry Heat Sterilization
Ex:
1.Incineration
2. Red heat
3. Flaming
4. Hot air oven
Moist Heat Sterilization
1.Dry saturated steam –Autoclaving
2. Boiling water/ steam at atmospheric
pressure
3. Hot water below boiling point

Dry Heat Sterilization
 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. It is also used for sterilizing non-
aqueous thermo stable liquids and thermo stable
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

Moist Heat 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.

Autoclave
Autoclaves use pressurized steam to destroy
microorganisms, and are the most dependable
systems available for the decontamination of
laboratory waste and the sterilization of
laboratory glassware, media, and reagents. For
efficient heat transfer, steam must flush the air
out of the autoclave chamber.
Generally the conditions employed are
Temperature upto121-134˚C for 15-20 min
under 15 lbs pressure,based on type of metiral
used.

Radiation Sterilization
 Many types of radiation are used for sterilization
like electromagnetic radiation (e.g. gamma rays and
UV light), particulate radiation (e.g. accelerated
electrons).The major target for these radiation is
microbial DNA.
 Radiation sterilization with high energy gamma rays
or accelerated electrons has proven to be a useful
method for the industrial sterilization of heat
sensitive products.
 Radiation sterilization is generally applied to articles
in the dry state; including surgical instruments,
sutures, prostheses, unit dose ointments, plastic
syringes and dry pharmaceutical products.

 UV light, with its much lower energy, and
poor penetrability finds uses in the
sterilization of air, for surface sterilization of
aseptic work areas, for treatment of
manufacturing grade water, but is not suitable
for sterilization of pharmaceutical dosage
forms.

Filtration Sterilization
 Filtration process does not destroy but removes the
microorganisms. It is used for both the clarification
and sterilization of liquids and gases as it is capable
of preventing the passage of both viable and non
viable particles.
 The major mechanisms of filtration are sieving,
adsorption and trapping within the matrix of the
filter material.
 Ex:HEPA FILTERS

 Sterilizing grade filters are used in the
treatment of heat sensitive injections and
ophthalmic solutions, biological products and
air and other gases for supply to aseptic areas.
 They are also used in industry as part of
the venting systems on fermentors,
centrifuges, autoclaves and freeze driers.
Membrane filters are used for sterility testing

There are two types of filters used in filtration
sterilization:
(a)Depth filters:
(b) Membrane filters: These are porous
membrane about 0.1 mm thick, made of
cellulose acetate, cellulose nitrate,
polycarbonate, and polyvinylidene fluoride, or
some other synthetic material

CHEMICAL STERILIZATION METHOD :
GASEOUS METHOD
 The chemically reactive gases such as
formaldehyde, (methanol, H.CHO) and
ethylene oxide (CH2)2O possess biocidal
activity. Ethylene oxide is a colorless,
odorless, and flammable gas.
 The mechanism of antimicrobial action of
the two gases is assumed to be through
alkylations of sulphydryl, amino, hydroxyl and
carboxyl groups on proteins and amino groups
of nucleic acids.

 The concentration ranges (weight of gas per
unit chamber volume) are usually in range of
800- 1200 mg/L for ethylene oxide and 15-100
mg/L for formaldehyde with operating
temperatures of 45-63°C and 70-75°C
respectively.
 Both of these gases being alkylating agents
are potentially mutagenic and carcinogenic.
They also produce acute toxicity including
irritation of the skin, conjunctiva and nasal
mucosa

IMPORTANCE OF STERILIZATION
Medical Sterilization :
 Prevents the Growth of Diseases:
In any medical tool/device used, bacteria comes
onto it. If left unchecked or not disinfected properly, it
is highly likely that bacteria will grow.
 Prevents the Spread of Diseases :
If surgical equipment is not properly sterilized,
patients treated are exposed to a disease the previous
patient had.
 Prevents Double Surgeries :
If unsterilized equipment is used, it can cause an
infection leading to another surgery later on in order to
remove it. This is costly and can cause many life-
threatening complications.

Heat sterilization
• Destroys bacterial endo toxinS
MERITS
Most widely used and reliable method of sterilization,
involving destruction of enzymes and other essential
cell constituents
DIMERITS
Can be applied only to the thermo stable
Products
APPLICATION
Dry heat is applicable for sterilizing glass wares and
metal surgical instruments and moist heat is the most
dependable method for decontamination of laboratory
waste and the sterilization of laboratory glassware,
media, and reagents.

Gaseous sterilization
MECHANISM :
• Alkylation
MERITS
 Penetrating ability of gases.
DIMERITS
 Gases being alkylating agents are potentially
mutagenic and carcinogenic
APPLICATION :
• ETHYLEN GAS HAS been used widely to
process heat-sensitive devices

Radiation sterilization :
MECHANCISM
• Ionization of nucleic acids
MERITS
• It is a useful method for the industrial sterilization of heat
sensitive products
DIMERITS
• Undesirable changes occur in irradiated products,an example
is aqueous solution where radiolysis of water occurs.
APPLICATION
• Radiation sterilization is generally applied to articles in the
dry state; including surgical instruments, sutures, prostheses,
unit dose ointments, plastic

Filtration sterilization :
MECHANISM
Does not destroy but removes the microorganisms
MERTIS:
It is used for both the clarification and sterilization of
liquids and gases as it is capable of preventing the
passage of both viable and non viable particles
DIMERTIS
Does not differentiate between viable and non viable
particles
APPLICATION
This method is Sterilizing grade filters are used in the
treatment of heat sensitive injections and ophthalmic
solutions, biological products and air and other gases for
supply to aseptic areas

Why we need Sterilization ?
 Microorganisms capable of causing infection
are constantly present in the external
environment and on the human body.
 Microorganisms are responsible for
contamination and infection.
 The aim of sterilization is to remove or
destroy them from materials or from surfaces.

Sterilization techniques .TYPES .MERTIES. AND DIMERTIES AND APPLICATION......

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