Disinfection and
Sterilization
Sterilization and disinfection
Sterilization
absolute absence of all viable microorgnisms, including
vegetative form and endospores
Disinfection
a process which reduces the number of contaminating
microbes, particularly those liable to cause infection
Bacteriostasis
to inhibit the growth of bacteria
Antisepsis
Asepsis
Disinfection is done to eliminate
as many microorganisms from
an item or from the environment
as possible, but does not
eliminate spores.
Disinfection is used when items
cannot or needn’t be sterilized or
in situations where no method of
sterilization is available
Sterilization
Sterilization is the process by
which all microorganisms,
including spores, are
destroyed
METHODS
Physical methods of disinfection
and sterilization
Chemical methods of disinfection
and sterilization
Physical methods
 Heat disinfection sterilization
 Illumination disinfection(radiation
sterilization)
 Ionization radialization
 Microwave disinfection sterilization
 Mechanical methods
heat disinfection sterilization
 Applied earliest, most reliable,most
extensively used
 Make use of the heat to destroy the
microorganisms’ protein,nucleic acid,cell
wall and cell membrane and cause the
microorganism’ death
Heat disinfection sterilization
 Dry heat and moist heat
dry heat----conduct the heat through the
air and the conduction is slow
moist heat---conduct the heat through the
steam and air,and the conduction is fast,the
penetration is strong
Heat disinfection sterilization
 Dry heat
burning method(incineration)
hot air drying method
 Moist heat
boiling water disinfection
steam under pressure sterilization
steam of low temperature under pressure
disinfection
flowing steam disinfection
Dry heat


Burning
Hot air drying
burning method(incineration)
 Character
Simple,fast,thorough
 Used for
contaminated wastes, Pathologic
specimens,dressings and paper with
purulent secretions,patients’corpses
 Method
directly burn or burn in incinerator
Especial points for burning method
 Additional use for
---oeses(接种环) used in microorganism
laboratory
 And used when in dire need(急需) for
---some metal instrments(but sharp knives
and scissors are exceptional to avoid blunting
them),and kinds of china
 Method
for metal instruments---cauterize
directly on the fire for 20 seconds
for china---pour alcohol of
95%~100% concentration into the china and
turn the container to make the alcohol
distribute evenly on the inside,then light up
the alcohol until the fire becomes dead for
itself
Hot air drying
 Make use of the specially made hot air
drying oven to sterilize, the heat power
spread and penetration depends on the
air convection and medium conduction,
and the effect of this method is reliable
 Suitable for
the articles that do not change in
character ,do not damage and do not
evaporate under high temperature.
For example: oil, powder,glass products
and metal products,etc.
Not suitable for
Fiber products, plastics products
The needed temperature and
time depends on the articles
character and the types of the
oven
Moist heat
*Boiling water
* Steam under pressure
 Steam of low temperature disinfection
 Flowing steam disinfection
Boiling water
 One of the earliest used methods of
disinfection
 Suitable for articles which are moiststable and temperature proof , e.g:
metals, china, glass, and latex, etc.
method
 Brush and clean the articles, drip them
into the water thoroughly, then heat
and boil the water.
 Timing starts from the boiling , if
anything added during the boiling,
timing starts from the second boiling
Points for attention
 Before use of this method, the articles
to be disinfected should be cleaned; the
instruments with axes and the
containers with covers should be
opened before they are placed into
water; the canals with cava should be
fully filling with water before
disinfection
Points for attention
 Too many articles being put into the
water at the same time are not
suitable;the basins and bowls of the
same size should not be laid to overlap
each other, one should ensure the every
sides of the articles to contact with the
water
Points for attention
 When to put the articles into the water and how
long the disinfection process lasts depends on the
kinds of the articles:
Kinds of articles When to put into Time for
the water
disinfection(min)
Glass products
Latex products
Cold water
10~15
Wrapped with
5~10
gauzes and when
the water is
boiling
Metals and china
10~15
Points for attention
 Mix Sodium bicarbonate into water to
make the concentration 1%~2% ,
which can cause the boiling point to be
105°C, and can enhance the effect of
killing bacteria and have the effect of
antirust and removing the dirties
Points for attention
 The boiling point of water is
influenced by the air pressure, and the
higher the elevation above the sea level,
the lower the air pressure and the
boiling point, so the disinfection time
need to be prolonged appropriately.
the elevation increases each 300m,
the disinfection time prolongs 2min
accordingly
Points for attention
The articles should be taken out
in time after being disinfected
and then placed them into
sterile containers
Steam under pressure
 The best effect among the heat
disinfection sterilization and applied
extensively in clinical settings
 Commonly used for the articles which
are heat-stable,pressure-proof, and can
bear damp,for example:instruments of
many kinds, dressings, china, latex,
glass and solutions,etc.
Steam under pressure
according to different way and degree of venting the
cold air, this method can be divided into two types
Steam under pressure venting
from the underneath(下排气式
压力蒸气灭菌)
Forevacuum steam under
pressure (预真空压力蒸气灭菌)
Steam under pressure venting from
the underneath(下排气式压力蒸气灭
菌)
 course: make use of the principle of Gravity
displacement to let the heat steam in the autoclave
down to drive the cold air out from the vents on
the underneath of the autoclave until the saturated
heat steam replace the cold air completely. When
the saturated heat steam becomes the vapour, it
will release latent heat, and it is just the latent heat
that can sterilize articles.
 Latent heat means the heat energy which 1g steam
of 100ºc releases when it becomes 1g water of
100ºc.
Steam under pressure venting
from the underneath(下排气式压
力蒸气灭菌)
When pressure is
102.97~137.30kpa, the temperature
in the autoclave can reach
121~126ºc, 15~30 minutes is
enough for sterilization
Forevacuum steam under
pressure (预真空压力蒸气灭菌)
 Course: make use of machine to
vacuumize the autoclave and make
negative pressure of 2.0~2.7kpa in it,
then the steam can rapidly penetrate
and reach the inner of the articles to
sterilize.
 When the pressure is 205.8kpa, the
temperature can reach 132ºc, 5~10
minutes are enough for sterilization
Points for attention
 The articles to be sterilized must be
cleaned and dried before put into the
autoclave
 The sizes of the packages should not be
too big. Or the packages should not be
too tight, the cubage of the packages is
appropriate for 30cmX30cmX30cm
 If the containers are with bores, the
bores should be opened when necessary
in order to let the steam in
Points for attention
 The packages should be placed
appropriately, there should be spaces
among the packages, and the kinds of
cloth should be placed onto the kinds
of metal and china
 The cold air in the sterilizer should be
let out as far as possible
 The articles being sterilized are not
taken out for use until they are dry
 Monitoring the sterilization effect
periodically
Steam of low temperature disinfection
 Steam of 73 °C ~80 °C in the
vacuumized sterilizer in advance , time for
10~15min
Can kill most of pathogenic microorganisms
 Mainly used for articles which are not heatstable, for example: endoscope, plastics and
rubber products
Flowing steam disinfection
 Steam of 100 °C under normal pressure,
time for 15~30min(timing starts from the
steam appearing)
 Commonly used for the tableware, bedpans
and urinals
Heat disinfection sterilization
Dry heat
burning method(incineration)
hot air drying method
Moist heat
boiling water disinfection
steam under pressure sterilization
steam of low temperature under pressure
disinfection
flowing steam disinfection
Illumination disinfection(radiation
sterilization)
 Make use of the
 Insolation under
ultraviolet rays to the sun
photolyze and
 Ultraviolet lamp
denaturalize the
disinfection
bacteria’s protein  Ozone lamp
and lead the
bacteria’s death
Insolation under the sun
The sun rays has the effects of heat,
drying and ultraviolet, so they can
kill bacteria in a certain degree—
they can make the protein of the
bacteria photolyze and denaturalize
and cause the bacteria dead
Insolation under the sun
Commonly used for mattress,
carpet,clothes,books.
Method:insolate the articles
directly under the sun for 6 hours,
and turn over the articles
periodically to make each side of
the articles exposure to the sun
Ultraviolet lamp disinfection
C wave,
wavelength:200~275nm, the
most effective:250~270nm
Ultraviolet rays can kill bacillus,
virus fungus, bacterial
vegetative form, spores.
Points for attention
 Because of its weak penetration power
and low radiant energy, this method is
mainly used for air and articles
disinfection
 The proper temperature is 20°C ~40
°C, and the proper humidity is
40%~60% for the lamp to disinfect
 The lamp need to be changed when it
has been used more than 1000 hours
Points for attention
 Timing starts from after the lamp is bright
for 5~7min
 There is 3~4min interval between two times
of lamp’ turning on
 After the lamp turned out , one should open
the windows to ventilate
 The effects should be monitored
periodically
 Keep the lamp clean, use the alcohol cotton
swab to wipe lightly in order to remove the
dirties and dust
Points for attention
 The ultraviolet rays can irritate the skin
and the eyes, and the generated ozone
during the irradiation is harmful to the
body, so one should go out of the room
being disinfected when the lamp is on,
and one should wear the protection
dress and the goggles .
Points for attention
Air disinfection: one 30w lamp at
each 10m2, the effective
distance:within 2m
The disinfection time:30~60min;
Points for attention
Articles disinfection: lay open or
hang up the articles to make their
surfaces directly exposed to the
ultraviolet light when disinfecting
The disinfection time:20~30min
Ozone lamp
 This method can be used to kill
bacterial vegetative form, virus, spores,
fungus and destroy botulin(肉毒杆菌
毒素)
 Mainly used to air disinfection,
hospital dirt water disinfection and
articles surfaces disinfection
Points for attention
 Because ozone is poisonous to human body,
persons must leave when the air disinfection
is ongoing, and go into the room again after
another 20~30min when the disinfection is
over
 The temperature , the humidity, PH, and
organic substances can influence ozone’s
effects of disinfection
The contents required to be studied by
oneself
Ionization radialization
Microwave disinfection
sterilization
Mechanical methods
Chemical Disinfection Sterilization
 If heat disinfection sterilization is not
suitable to use for some objects,
chemical disinfectin sterilization can
be considered, for example:the
disinfection of skins, mucous
membranes, excretions and
surrounding environments optical
instruments, keen metals and some
plastics
Chemical Disinfection Sterilization
The chemicals used for
disinfection are called as
disinfectants. The effects of some
disinfectants are enough strong to
sterilize, these disinfectants are
also called as sterilants.
The effects types of disinfectants
Effects level
Disinfectants
examples
High level
Ethylene oxide,
peracetic
acid ,kinds of
aldehyde
Kinds of alcohol,
kinds of iodine,
chloric
disinfectants
Chlorhexidine,
phenolic
disinfectants
Normal level
Low level
Chemical disinfectants use
principles
 Select the proper disinfectants according to
the types of the objects to be disinfected and
the characters of the microorganisms to be
killed
 Strictly control the effective concentration of
the disinfectants and the disinfection time ,
the use methods
 The disinfectants should be changed
periodically, the disinfectants which vaporize
easily should be covered and examine and
regulate its concentration
Chemical disinfectants use principles
 The objects must be cleaned and dried
beforehand
 There should not be the gauzes, cotton and
so on in the disinfectant solutions, for these
kinds of objects can absorb the disinfectants
so that the effect of the disinfectants can be
weakened.
 The objects after being disinfected must be
rinsed with physiological saline(生理盐水)
before use to protect body tissues from the
disinfectants’ irritating
use methods of chemical
disinfectants
Immersion:
Firstly, clean the articles to be disinfected,
secondly, dry the articles, then, immerse the
articles into the disinfectant solution.
Attention to open the axes or the covers of
the articles and fill the tubes fully with the
disinfectant solution.
Immersion time and the concentration of the
solution should be according to the
provision.
use methods of chemical
disinfectants
Rubbing:
Which is the method to use the chemical
disinfectants to rub the surfaces of the
contaminated articles or the method to
disinfect the skin.
e.g:using iodophor of 0.5%~1.0% to disinfect
skin; using chloric disinfectants to rub the
walls and the floors.
use methods of chemical
disinfectants
Nebulization
The method is that using a nebulizer spray the
chemical disinfectants evenly on the
surfaces of articles or the air.
The method is commonly used for the
disinfection of floors, walls, and
environment, etc.
Attention to wet the articles’ surfaces well
when one spray.
use methods of chemical
disinfectants
Fumigation
The method means creating air to disinfect through
heating a disinfectant or add oxidants into it.
The method is commonly used for disinfection of
space, e.g: the space of operation rooms, dressing
rooms and wards.
And in the closed containers this method can also be
used to disinfect the contaminated articles.
The formaldehyde gas and ethylene oxide gas are
commonly used
The commonly use chemical
disinfecants
 Alcohol（酒精）
 Iodine tincture（碘酊）
 Iodophor（碘伏）
 Hibitane(chlorhexidine)（洗必泰）
 Peracetic acid（过氧乙酸）
 Ethylene oxide（环氧乙烷）
 Formalin（福尔马林）
 Glutaraldehyde(戊二醛)