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 infectionBacteriostasis to inhibit the growth of bacteria

AntisepsisAsepsis

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

SterilizationSterilization 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 moist-stable 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 the water

Time for disinfection(min)

Glass products Cold water 10~15

Latex products Wrapped with gauzes and when the water is boiling

5~10

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 heat-

stable, 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 sterilizationDry heat

burning method(incineration)

hot air drying methodMoist 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 ultraviolet rays to photolyze and denaturalize the bacteria’s protein and lead the bacteria’s death

Insolation under the sun

Ultraviolet lamp disinfection

Ozone lamp

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

Normal level Kinds of alcohol, kinds of iodine, chloric disinfectants

Low level Chlorhexidine, phenolic disinfectants

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 NebulizationThe 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 FumigationThe 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 )