UNIT 2.
2
METHODS OF STERLIZATION
SADIQ ALI CHANDIO
NURSING INSTRUCTOR
COLLEGE OF NURSING MALE
LARKANA
OBJECTIVES
At the end of presentation participates will be able to:
Describe some physical and chemical methods to control
microbial growth .
METHODS OF STERLIZATION
1. Physical Methods of sterilization
1. HEAT Methods of microbial Control: Kills
microorganisms by denaturing their enzymes and
other proteins.
(a) Moist heat (autoclave)
(b) Dry heat (Flaming, hot air oven, incineration)
2. Radiation (X Rays-UV Rays)
3. Filtration
2. Chemical method of sterilization
1. Gases (Ethylene oxide, Formaldehyde)
2. Liquids (Glutaraldehyde-Iodine- Hydrogen per oxide)
DRY HEAT …….
This is less efficient process as compared to moist heat.
This process is used primarily for glassware and is used
less frequently than autoclaving. Bacterial spores are
most resistant to it. Spores may require following
temperature:
140°C for 3 hours
160°C for 2 hours
170 °C for 1 hour
180 °C for30 minutes
DRY HEAT….
Flaming: Dry heat includes flaming which is done in
microbiology laboratories to sterilize instruments.
It is a method of choice for fine metal canulla such as
lumbar puncture needles
It is also used to sterilize oily pharmaceutical
preparations and powders.
Hot air oven: It is used for sterilization of glassware,
glass syringes, metal instruments and oil.
MOIST HEAT……(AUTOCLAVING)
High Steam under pressure:
Steam under pressure is used in autoclaves has physical
properties which allow rapid penetration of heat through
surgical instruments, linen and OT fabrics.
In this temperature greater than 121°C for 15 minutes or
126°C for 10 minutes or 134°C for 3 minutes is required
to kill spore.
Low steam under pressure:
This is method of killing all vegetative organisms and
some spores present on heat sensitive equipments such
endoscope when combined with formaldehyde on 80°C
for 30 minutes to 2 hours in autoclave machine.
RADIATION….
Both ionizing (such as alpha, beta, and x-
rays) and non ionizing (ultraviolet light)
radiation are used for disinfection and
sterilization. The main drawback to
ultraviolet light is that the rays do not
penetrate deeply.
Ionizing radiation is used effectively in
industry to sterilize foods, drugs, and other
items that are sensitive to heat.
Its main advantage is that it is effective for
items difficult to sterilize; its chief
disadvantage is that the equipment is very
expensive
X-RAYS:
X-rays have higher energy and penetrating power than UV
radiation and kills mainly by the production of free radicals,
which can break covalent bonds in DNA, thereby killing the
organism-rays are used in medicine for sterilization of heat
sensitive items, such as sutures and surgical gloves.
UV Light:
The greatest antimicrobial activity of UV light occurs at 200-280
nm of wavelength at which DNA replication is inhibited and the
organism cannot grow. Radiation destroys the DNA of multiple
microbes. It is used for sterilization of disposable instruments
which are used for single useful radiation can damage cornea and
skin. The use of UV radiation in medicine is very limited.
It is used for sterilization of drinking water.
FILTRATION:
It is preferred method of sterilizing certain solutions,.
The solutions now are now filtered to make them
“pyrogen free” before autoclaving. In filtration a filter
with a pore size of 0.2 µm is used. These sizes will
retain all bacteria and spores. Filters work by physically
trapping particles larger than the pore size of filters.
It is used for clarification of water impurities and
determination of virus particles.
STANDARD PRECAUTIONS
Standard precautions are used in the care of all hospitalized
individuals regardless of their diagnosis or possible
infection status. They are used in any situations involving
blood, all body fluids, excretions, and secretions except
sweat (whether or not blood is present or visible), non
intact skin, and mucous membranes. SP include:
(a) hand hygiene
(b) use of personal protective equipment (PPE), which
includes gloves, gowns, eyewear, and masks; (c) safe
injection practices
(d) safe handling of potentially contaminated equipment or
surfaces in the client environment; and (e) respiratory
hygiene/cough etiquette.
2.CHEMICAL METHOD
(A) GASES: Ethylene oxide (E.O)
Formaldehyde
Ethylene oxide is an alkylating agent most widely used in
gases sterilization. It is active against all types of bacteria
and their spores. It
\’]penetrates rapidly through rubber, plastics and destroys
micro organisms.
It is effective for the sterilization of syringes, catheters, urine
bags, sterile surgical gauze pads which are damaged by heat.
Formaldehyde (formalin) is a gas that is usually used in 37%
solution. Formalin Vapors are usually used to disinfect
operation theatre and rooms to destroy bacteria and their
spores. The temperature of vapors should be 70-80°C
LIQUIDS (GLUTARALDEHYDE-IODINE-CHLORINE-
HYDROGEN PER OXIDE)
ALCOHOL (SPIRIT):
Ethanol is widely used to clean the skin before immunization and
veinipuncture.It is used for skin antiseptic and surface disinfectant.
The percentage of alcohol in 70% is effective than 100%.
FUMIGATION:
Formaldehyde vapors are used to disinfect Operation Theater. The
temperature of vapors should be 70-80 ˚C
SILVER NITRATE:
Silver nitrate drops are used for gonococcal ophthalmic
neonatorum.It has great antibacterial activity. Silver sulphadiazine
is used to prevent infection of burn wounds. Mercurochrome which
contains mercury is used as skin disinfectant.
POVIDONE-IODINE:
It is most important skin disinfectant and is used for sterilization of
surgical instruments as well as for dressing of chronic wounds.
CHLORINE: It is most useful water disinfectant.3% solutions are a
harmless but very weak disinfectant used for cleansing of wounds.
HYDROGEN PER OXIDE: in a 3% solution is harmless but weak
disinfectant used in cleansing of wound. It is an oxidizing agent that
attacks sulfahydryl groups, thus inhibiting enzymatic activity.
POTASSIUM PERMAGNATE: is another oxidizing agent which
is used in the treatment of urethritis and skin infections.
REFERENCES: KEYS
Microbiology for nurses sood
3rdedition
Medical microbiology& immunology 4th
edition wareen E levinson ernest jawetz
(page 66)
General text book of nursing 19th edition
evelyn pearce.
Textbookofmicrobiologyfornurses2ndedition
Htp//dk.com
htp// goggles www.asepsis methods.com
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