DISINFECTION AND STERILIZATION IN ENGLISH
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DISINFECTION-
} Disinfection is a process
of killing harmful microorganism (excluding bactirial spores) present of any
instrument or object. It is very effective in
infection prevention activities. Disinfection can reduce expenditure of
treatment of diseases.
} Disinfectant- it is a chemical or physical agent
that destroys disease causing pathogens or other harmful microorganisms It refers to substances applied to inanimate
objects to disinfect it
CHARACTERISTICS OF A GOOD DISINFECTANT-
} 1. disinfectant should have a wide
antimicrobial spectrum.
} 2. It should be a fast killer.
} 3. it should be active in the
presence of organic matter (e.g., blood, sputum, faeces)
} 4. it should not harm instruments and
metallic surfaces, and should not cause the deterioration of cloth, rubber, plastics,
and other materials.
} 5. It should have a pleasant odour or
no odour to facilitate its routine use
} 6. It should not be too costly to
afford.
} 7. It should be soluble in water so
that can be diluted as per desired concentration.
} 8. it should be ecofriendly and not
damage the environment on disposal.
CLASSIFICATION OF DISINFECTANTS-
} Disinfectants may be classified as-
} Natural disinfectants- Natural Disinfectants are air and sunlight. Exposure to open air
(airing) acts by drying or evaporation of moisture which is lethal to most
bacteria. In the same way Direct and
continuous exposure to sunlight is destructive to many disease producing
organisms. The ultraviolet rays of sunlight
are particularly lethal to bacteria and some viruses.
} Physical disinfectants- (1) Burning : Burning or incineration is an excellent
method of disinfection. Inexpensive articles such as contaminated dressings,
rags and swabs can be disposed off by burning. Addition of sawdust, paper,
kerosene or other combustible material aid in burning. Faeces can be disposed
off by burning.
} (2) Hot air : Hot air
is very useful for sterilizing articles such as glassware, swabs, dressings,
oils, vaseline and sharp instruments. Hot air disinfection is usually done in a
hot air oven.
} (3) Boiling : Boiling is an
effective method of disinfection. It provides an atmosphere of boiling and
steam. Boiling for 5-10 minutes (rolling boil) will kill bacteria, but not
spores or viruses.
} Chemical disinfectants- Phenol and cresol: Phenol or carbolic acid is a chemical disinfectant. Pure phenol is not an
effective disinfectant. Crude phenol (mixture of phenol and cresol) is an
effective disinfectant. 10 per cent strength for disinfection of faeces. In 5
per cent strength, it may be used for mopping floors and cleaning drains.
} Cresol alone is also an excellent
disinfectant. It is more powerful than
phenol, yet no more toxic. Cresol is best used in 5 to 10 per cent strength
for disinfection of faeces and urine.
Cresol is an all-purpose general disinfectant.
} Cresol emulsified with soap is known
as "saponified cresol". Lysol, izal and cyllin are cresol emulsions.
Lysol contains 50-60 per cent cresol. They are very powerful disinfectants. A 2
per cent solution of lysol may be used for disinfection of faeces.
} Chlorhexidine : This is one of the most useful skin
antiseptics. It is soluble in water and
alcohol. It is inactivated by soaps and detergents. 0.5 per cent alcoholic or
aqueous solutions can be used as effective hand lotions. Creams and lotions containing
1 per cent chlorhexidine are recommended for burns and hand disinfection.
} Hexachlorphane : This disinfectant is highly active
against gram-positive organisms. It is slow in action, but shows a cumulative
effect on the skin and is compatible with soaps. Thus it may be incorporated in
soap preparations without loss of activity.
} Chloroxylenol: chloroxylenol is a relatively
non-toxic antiseptic and can be used safely in high concentrations. It is more
easily inactivated by organic matter than many other phenolic disinfectants. 5%
solution is suitable for disinfection of instruments and plastic equipment; a
contact of at least 15 minutes will be required for disinfection.
} Cetrimide : It is an ammonia compound. It is
actively bactericidal against vegetative gram-positive organisms, but much less
so against gramnegative organisms. it has a soapy feel. It may be used in 1-2
per cent strength.
} Bleaching powder: Bleaching powder or chlorinated lime
(CaOCl2) is a white amorphous powder with a pungent smell of chlorine. It kills
most of the organisms when used in the strength of 1 to 3 percent. Bleaching
powder is widely used for disinfection
of water, faeces and urine; and as a deodorant.
} Hypochlorites : Hypochlorites are the most widely
used chlorine disinfectant, available as liquid (e.g. sodium hypochlorite) or solid (e.g. calcium
hypochlorite). They have a broad spectrum of antimicrobial activity, do not
leave toxic residues. it is used for large scale sanitization activities
} Iodine: Iodine solutions or tinctures have
been used by health professionals primarily as antiseptic on skin (e.g.to
prepare incision site prior to surgery) or tissue since long time. Iodine is
bactericidal, fungicidal, virucidal and lethal to spore-bearing
organisms. Iodine is cheap, readily available and quick in action.
} Alcohols: Ethyl and isopropyl alcohols are
commonly used as antiseptics and disinfectants. Ethyl alcohol in the form of
industrial methylated spirit is the alcohol most commonly used for skin disinfection
and hand sanitization. Pure alcohol has no powers of disinfection but 70% solution is potent bactericidal, fungicidal
and virucidal
} Formaldehyde: It is effective against vegetative
bacteria, fungi and many viruses but only slowly effective against bacterial
spores and acid-fast bacteria. It does
not injure fabrics and metals. It may be used as a 2-3 per cent solution for
spraying rooms, walls and furniture. Formaldehyde gas is most commonly used for
disinfection of rooms
} Potassium permanganate : It is a purplish black crystalline oxidizing agent . It is
used to disinfect aquariums and is also widely used in community swimming pools
to disinfect ones feet before entering the pool. It is also used to disinfect
fruits and vegetables.
} Hydrogen peroxide: Hydrogen peroxide is bactericidal, virucidal, sporicidal and
fungicidal. It is used in hospital setting to disinfect surfaces. A 0.5 per cent hydrogen peroxide demonstrated
bactericidal and virucidal activity in 1 minute and mycobactericidal and
fungicidal activity in 5 minutes. A 3 per cent solution is also used as an
antiseptic and for cleaning wounds and discharging ulcers.
TYPES OF DISINFECTION-
} Disinfection is classified into three
types-
} 1) concurrent disinfection- Concurrent disinfection is defined as “disinfection of infectious material as soon as it is
discharged from the body of an infected person, or after the soiling of
articles with such infectious discharges” . In other words, the pathogenic
agent is destroyed as soon as it is released from the body, and in this way
further spread of the agent is stopped.
} Concurrent disinfection consists of
usually disinfection of urine, faeces, sputum, vomitus, contaminated linen,
clothes, hands, dressings, aprons, gloves, etc. throughout the course of an
illness. This disinfection is carried out time to time during stay of the
patient in the unit.
} 2) Terminal disinfection- Terminal disinfection is defined as “disinfection of infectious material after discharge or death
of the patient. way further spread of the agent is stopped. Terminal
disinfection includes disinfection of instruments, furniture,bedding and
room/unit (using formaldehyde gas)
} 3) prophylactic disinfection. - Prophylactic disinfection is defined as disinfection
before starting of disease. Disinfection of water by chlorine, pasteurization
of milk and handwashing may be cited as examples of prophylactic or precurrent
disinfection
STERILIZATION-
} Sterilization is a process used to
make a product free of all forms of viable microorganisms including bacterial
spores. This process is essential in surgical procedures. All instruments used
in surgery should be sterilized before using.
METHODS OF STERILIZATION-
} Autoclaving : autoclaving is very
effective method of sterilization. Sterilizers which operate at high and pressure are called autoclaves. They
generate steam under pressure (saturated steam) which is the most effective
sterilizing agent.
} Autoclaving is widely used in
hospital and laboratory practice. It destroys all forms of life, including
spores. Steam attains a higher temperature under pressure, and has greater
powers of penetration than ordinary steam. Normally autoclaving is done at 121
degree centigrade and 15 psi pressure for 15 minutes
} Radiation: Ionizing radiation is used for sterilization of bandages,
dressings, catgut and surgical instruments. The objects to be sterilized are
placed in plastic bags before radiation, and they will remain sterile until
opened. Ionizing radiation has great penetrating powers with little or no
heating effect.
} Ethylene Oxide gas : Heat-sensitive articles may be
sterilized at 55-60 degree Centigrade by
ethylene oxide gas which kills bacteria, spores and also viruses. Ethylene oxide is
explosive, therefore, it is mixed with carbon dioxide and Water vapour is also
often added to the mixture as it
increases the efficiency of the gas.
} Microwave: Microwaves are used
for sterilization of soft contact lenses, dental instruments, dentures,
milk, and urinary catheters for intermittent self catheterization. The
microwaves produce friction of water molecules in an alternating electrical
field. The intermolecular friction derived from the vibrations generates heat.
The microwaves produced by a microwave
oven (2.45 GHz) completely inactivate bacterial cultures, mycobacteria and
viruses.
} Ultraviolet radiation : The
wavelength of UV radiation ranges from 328 nm to 210 nm. Its
maximum bactericidal effect occurs at 240-280 nm. UV radiation is used in the sterilization of water, air, titanium implants and contact
lenses. Bacteria and viruses are more easily killed by UV light than the
bacterial spores.
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