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STERILISATION,
DISINFECTION & ASEPTIC
TECHNIQUE
Presented by
Mrs C.B. Bello
CHAIN OF INFECTION
• An infection is the invasion of a susceptible host by
pathogens or microorganism resulting in disease.
• The presence of a pathogen does not mean an
infection will occur. Infection occur in a cycle that
depends on the presence of all of the following
elements:
An infectious agent or pathogen
A reservoir or source for pathogen growth
A port of exit from the reservoir
CHAIN OF INFECTION CONTD
A mode of transmission
A portal of entry to a host
A susceptible host
INFECTIOUS AGENT
• Micro-organisms include bacteria, viruses, fungi,
and protozoa.
• When on the skin, can be resident or transient.
Residents micro-org (normal flora) are permanent
residence on the skin, they multiply and survive
without causing dx.
• Factors that affect potential of micro-organism to
cause dxes are: the number of micro-organism
present, the susceptibility of the host, the virulence
of the micro-organism,
• Resident micro-organism do not cause dx except
INFECTIOUS AGENT CONTD
• When invasive procedures allow them to leave
normal abode and enter into deep tissues. Or when
the host is immuno-compromised (have an
impaired immune system).
• Transient micro-organisms attach to the skin when a
person come in contact with another person or
objects during normal activities e.g., contaminated
clothing's and dressings.
• This micro-organisms can easily be removed
through effective hand hygiene.
A RESERVOIR
• A reservoir is the place where micro-organisms
survive, multiply, and await transfer to a susceptible
host
• Common reservoir are human and animal host,
insects, food water and or organic matters or
inanimate surfaces (fomites)
• Frequent reservoirs for health care associated
infections are, health care workers, especially their
hands, patients, equipments and the environment.
• Human reservoir can be those with acute or
symptomatic disease or those who show no
symptoms but are carriers of the disease.
MODES OF TRANSMISSION
• Direct transmission:
 direct contact , skin to skin, mucosa to mucosa, skin to
mucosa
 droplet infection, from coughing, sneezing, speaking
 contact with soil
 inoculation into skin or mucosa
• Indirect transmission:
 vehicle borne; water, food, raw veg, fruits, milk & products
 Vector borne; cockroaches, flies, mosquito, rodents etc
 Airborne
 Fomite-borne; towels, linen, handkerchief, sphyg etc
 Unclean hands & fingers
MODES OF TRANSMISSION CONTD
• Each disease has a specific mode of transmission
• Major routes of transmission in health care settings
are:
o unwashed hands of health care workers
o equipments, e.g. stethoscope, blood pressure cuff,
bedside commode.
PORT OF ENTRY
• Organisms enter the body through the same routes
they use for exiting e,g a needle a patients skin,
organism enters the body if proper skin preparation
are not performed.
SUSCEPTIBLE HOST
• This is individuals degree of resistance to
pathogens.
• Even when an individual is exposed to lots of microorganisms, an infection does not occur until an
individual become susceptible to the strength and
number of the microorganism
• A persons natural defense is important
• A persons age, nutritional status, presence of
chronic disease, trauma, smoking are factors that
affect the susceptibility to infection.
CONCLUSION
• Your understanding of the chain of infection is to
provide knowledge that is vital in understanding
that the procedures of sterilization, disinfection and
practices of surgical asepsis are measures to break
the chain of infection at one point or the other in
order to prevent transmission of infection.
DEFINITION OF TERMS
• Asepsis: it’s the absence of pathogenic (diseaseproducing) microorganisms.
• Aseptic technique: Practices/ Procedures that help
reduce the risk of infection. There are 2 types of
techniques. Surgical & medical asepsis
• Medical Asepsis: this is referred to as the clean
technique, the aim is to reduce the number of
microorganism present in a field and preventing
further transfer of organism. Medical asepsis
measures include hand hygiene, barrier technique
& routine environmental cleaning.
DEFINITION OF TERMS CONTD
• Medical asepsis is commonly practiced at home, on
medical wards etc.
• Surgical asepsis: it is also referred to as surgical
technique. The aim is to eliminate all
microorganism including there spores present in a
field, measures include surgical hand scrub,
sterilization of equipments & articles, using of
sterile drapes etc. this principle is commonly used
for surgical procedures such as surgeries, wound
dressing, catheterization, parenteral drug
administration etc.
DEFINITION OF TERMS CONTD
• Contamination: this is when an object come
in contact with an infectious or potentially
infectious material. The object is discarded if
disposable but if reusable, it is cleaned,
disinfected or sterilized depending on use.
• Sterile
STERILISATION
INTRODUCTION
• Sterilisation is the process whereby all microorganisms (pathogenic & non-pathogenic) including
their spores are destroyed. An item become sterile
following sterilisation.
• The term “sterile’’ is an absolute term, an item is
either sterile or not sterile, there is nothing like near
sterile or almost sterile.
• Pathogenic micro-organism are those that are
capable of causing infection if they get introduced to
the body tissues
• It is important that hospital provide specific
• principles and practices for sterilization of all items
safe for use and reduces the transmission of
infection as long as sterility is maintained.
• Bacteria spores are the most resistant of all living
organisms because of its ability to withstand
external destructive agents, therefore, any method
that is not capable of destroying spores is not
referred to as a sterilization method.
• The selection of a sterilization method depend
primarily upon the nature of items to be sterilized.
METHODS OF STERILIZATION
• There are physical and chemical methods.
• 1. Physical methods
a)Moist heat (steam under pressure or
autoclaving)
b)Dry heat (hot air oven)
c) Radiation
2. Chemical methods
a)Ethylene oxide gas
b)Vapour phase Hydrogen Peroxide
MOIST HEAT
• Most efficient method, popular in the hospital &
reliable. Moist heat in form of steam under pressure
is a reliable physical agent in the destruction of
microbes including their spores, at temperature of
1210c for 15mins under great pressure or a flash
sterilization at 2700c for 3mins.
• Death of micro-organism is by denaturation &
coagulation of protein system of the cell.
• A special equipment called autoclave is required, an
autoclave is like a jacket inside another jacket,
steam is formed and introduced into equipments/
• materials in the inner chamber under a very high
pressure for the stipulated period of time.
• Precautions
– Items must be free from grease, oil or stain
– Materials must be arranged to allow flow of air
– Timing of cycle must be adjusted for different
materials
• Suitable for stainless steel materials such as
bowls, gallipots, receivers, instruments, linens,
rubber goods, dressings, glassware
• Not suitable for powders and anhydrous oils.
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Advantages:
Easiest and safest
Very reliable and efficient
Fastest method
Least expensive and available
Has no harmful residue
Disadvantages:
Special precautions is required in preparing,
packaging, loading and operating an autoclave
DRY HEAT
• Dry heat in form of hot air at 1600c for
2hours using a hot air oven is used for
heat stable materials, glass-wares, glass
syringes, capillary tubes, slides, needles,
oils and powders.
• Destroys microorganism by coagulating
the protein unit of the cell of the
microorganism. Commonly used in
medical laboratory to sterilise items such
• Advantages
-Hot air penetrates certain substances that cannot be
autoclaved or may be damaged by moisture
-suitable for goods that cannot be disassembled.
• Disadvantages
-long exposing period is required because hot air
penetrates slowly & unevenly.
-over exposure to heat may ruin substances or
materials
-it’s destructive to fabrics and rubber goods.
RADIATION
• Used mainly in industries, packaged materials
such as pre-packed disposable syringes,
catheters, Naso-gastric tubes, sterile gloves
etc.
• Both ionizing (alpha, beta rays & x-ray) and
non ionizing (ultraviolet) radiation are used for
disinfection & sterilization but ultraviolet rays
do not penetrate deeply
• Ionizing radiation is used in industry more
effectively to sterilize foods, drugs, & above
• Advantages:
-Good for sterilizing bulky items even in their
cartons ready for shipment
-Effective for items that are difficult to
sterilize e.g. If both sensitive to heat and
moisture.
• Disadvantages
-Equipment for sterilization is expensive
ETHYLENE OXIDE GAS
• Used to sterilise items that are heat or
moisture sensitive effective at low
temperature.
• It interferes with normal metabolism of
protein & reproductive process resulting
in the death of cells.
• Its used in gaseous state, highly
inflammable & explosive hence
usedalong with an inert gas (CO2)
• Advantages
-Provides effective method for goods that can be
damaged by moisture.
-Has good penetrating power
-Compatible with most medical material
• Disadvantages
-Expensive
-Leaves toxic by products
-Highly inflammable & explosive
-If inhaled, can be irritating to the mucous
membrane
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CENTRAL STERILE SUPPLY DEPT (CSSD)
Cleaning disinfection & sterilization of client’s
supplies should be performed in the CSSD, this unit
should be responsible for all the sterile supplies
needed in all the wards & units of the hospital
The department should be divided into several
areas separated by physical barriers.
Monitoring sterilization process is important in the
CSSD to ensure efficiency.
Temperature in the CSSD should be 18oc -22oc while
humidity should be between 35% -70%
Airflow should be directed from clean to relatively
soiled areas
DISINFECTION
DISINFECTION
• This is the process of destroying all micro-organism
except spores (Rutala & Weber, 2009).
• METHODS OF DISINFECTION
• Boiling: most micro-organism are killed by 5mins
boiling at 100oc, spore forming organism &
thermophillic micro-organism are not, hence not
sporicidal
• Equipments cannot be guaranteed sterile if processed in
this manner, instruments, stainless / enamel/ steel such
as bowls, kidney dishes, urinal, bedpans are sterilised
using such method.
• Lensed and sharp edged instruments should not be
boiled.
• Pasteurization: this is immersion in water at 75oc –
850c for 10mins, commonly used for lensed
instruments (endoscopes). A thermostatically
controlled water bath is used, non boilable
instruments can withstand this.
• Formalin vapour + steam under pressure:
dismantled instruments are exposed to formalin
vapour with steam under atmospheric pressure e.g.
lensed instrument.
• Sunning: pillows, mattresses, sandbag
• Freezing: food and drinks
• Chemicals: are capable of destroying microorganism.
CLASSIFICATION OF CHEMICAL DISINFECTANTS
• Low level disinfectants: can kill only vegetative bacteria &
enveloped viruses but not the tubercle bacilli, spores or
small & non-lipid (non-enveloped) viruses, though it may
kill fungi after prolonged contact.
• Intermediate level disinfectants: kill vegetative bacteria,
tubercle bacilli, fungi & enveloped viruses, has no effect on
spores &non enveloped (non-lipid) viruses at normal
contact times
• May exhibit limited virucidal (against non-enveloped)
activity on prolonged contact. (chlorine compounds,
alcohols).
• High level disinfectants: kill all except spores, are capable
of actual sterilization at extended contact times. (2%
Glutaraldehyde, may be sporicidal when activated (Cidex),
Chlorine dioxide, Peracetic acid
FACTORS AFFECTING DISINFECTANTS
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Chemical component
Concentration of solution
pH of the medium
Temperature of environment (best at room temp)
Volume
Duration of contact
Length of storage
FACTORS AFFECTING DISINFECTANTS
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Nature & amount of contamination
Presence of inactivating substances
Surface areas to be disinfected
Prior cleaning to remove organic material-blood,
pus, saliva, body excretions.
• Presence of soap- soap causes certain disinfectants
to be ineffective
• Always use disinfectants according to manufacturers
instruction.
• Disinfectants must be supplied by the pharmacy at
RATIONALE FOR CHOICE OF PROCEDURE
• Based on categorizing medical devices, equipments
and surgical materials on basis of risk of causing
infection.
• The “Spaulding” classification is a traditional
approach used to determine the level of disinfection
or sterilisation required for reusable medical devices
based on the degree of risk for transmitting
infections if the device is contaminated at the time
of use.
• Critical
• Semi-critical
CRITICAL ITEMS
• Instruments or objects that will be introduced
directly into the body tissue or blood stream or into
other normal sterile areas are critical items.
• Examples are: Surgical instruments, implants, blood
compartment of haemodialyzer, cardiac,
intravascular or urinary catheters etc.
• The minimum standard required is sterilization.
SEMI-CRITICAL ITEMS
• This are items that come in contact with intact
mucosal surfaces but do not ordinarily penetrate
body surfaces
• There is intermediate risk of causing infection, for
example, non-invasive flexible and rigid
endoscopes, endo-tracheal tubes, cystocopes,
diaphragm fitting rings.
• Sterilisation is preferred but not absolutely
essential, a high level disinfection procedure that
can be expected to destroy vegetative microbes,
most fungal spores, tubercle bacilli & small nonlipid viruses can be recommended.
NON-CRITICAL ITEMS
• These are items that come in contact with intact skin
but not mucous membranes
• They have a low risk of transmitting infection .e.g.
crutches, blood pressure cuffs, stethoscopes,
tourniquets, bed rails, food utensils, bedside trays,
bedpan
• Cleaning with water & detergent may be adequate
but a low level disinfectant may be preferred in all
cases
PRECAUTIONS
• Rinse all items to be sterilized or disinfected thoroughly in
cold water using a brush & soap under running water
• Take extra care to remove blood stain, dirt, clots, oil or
grease from items.
• Dismantle where possible so that heat/steam/chemical can
penetrate all parts of the article
• Arrange items to allow free flow of chemicals/steam/heat
• Dry items properly after washing/ cleaning before
commencing on any method of sterilisation/disinfection
• During disinfection, ensure that items are properly
immersed, allow solution to cover the items
• Leave items in solution for a stipulated length of
time
• Consider that the method of sterilization/
disinfection chosen is appropriate for a particular
item
• Follow all important details or information about
your method. e.g. packaging & loading in
autoclaving & strength of chemicals or any special
information concerning the machine in use.
• Use cold water rather than hot in washing items, use
soap if oily.
EXAMPLES OF DISINFECTANTS/ ANTISEPTICS
• Phenolics: has bactericidal effect in 10mins, usually
corrosive, used with bedpans shelves, incubators, floors,
walls slashed with exudates, linen. Examples, Carbolic acid,
Lysol, Sudol, Izal, Hexachlorophene
• Halogens & halogen containing compounds: has
bactericidal effect, used in cleaning floors, walls, glassware,
to irrigate wounds. Examples, iodine, chlorine compounds
such as Eusol. Hypochlorite (Jik)Iodine stains, chlorine
bleaches & its corrosive
• Aldehydes: capable of disinfection by precipitating protein
in the cell of bacteria, widely used for lensed instrument, its
expensive.
• Diguanides: e.g. Chlorhexidine (hibitane) a wide
spectrum antisceptics, e.g. Hibitane 4% in detergent
(Hibiscrub) used for surgical hand scrub, used with
ethyl alcohol to disinfect lensed instrument,
aqueous dilution of 1% used for vaginal douche or
for cleaning fresh wounds
• Quanternary Ammonium compounds: e.g.
Cetrimide– 1% in soap Phisottex) used in skin
preparation during surgery
• Heavy metals
• Mercurial- precipitate protein & inhibit production of useful
enzymes in the cell, highly toxic example, Mercurial
bichloride used in disinfection of unbroken skin.
• Silver nitrate: silver nitrate 1 in 1,000 useful in gonococcal
infection of the eye in the newborn, reduces infection in
burns wound.
• Oxidising agents: this agent exert microbial actions by
oxidation
– Hydrogen peroxide- to disinfect wound
– -Potassium permanganate- used in wiping skin lesions, 1
in 1,000
RULES FOR USE OF DISINFECTANTS
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Follow manufacturer’s instruction
Check expiry date of solution
Ensure optimum dilution
Always wash and clean articles before disinfection
Do not refill disinfectant containers between each use,
topping up is not allowed
• Disinfectant should be supplied ready for use from the
pharmacy
• Return empties to pharmacy- do not discard or use for other
purpose
• Where disinfectant are indicated for use on the surface,
WIPE, DO NOT BATHE
CLEANING
• Cleaning is the removal of organic & inorganic
substances from objects or surfaces (Rutala &
Weber, 2009).
• It involves the use of water and detergents with
mechanical force.
• Reusable objects must be properly cleaned when
they come in contact with infectious or potentially
infectious materials before they are taken through
the process of sterilization and disinfection.
CLEANING CONTD
• Cleaning is an essential preparation of equipment
prior to sterilization or disinfection as the presence
of organic matters in items reduces the
effectiveness of sterilizing and disinfecting agents.
• Cleaning with water & disinfectants removes
contamination physically
• Staff must wear protective clothing (water proof
gloves) while carrying out cleaning
• Water must be below 45o to prevent protein
coagulation of organism on the instrument being
cleaned.
• The articles must first be rinsed with cold running
water to remove organic materials such as blood,
fecal matter, mucus, or pus.
• Avoid the use of hot water as this coagulate the
protein of the organic materials, this becomes very
difficult to remove
• Wash the articles after rinsing them in warm water
that contains detergent, the combination of warm
water and soap facilitate emulsification and
removal of dirt, oil, grease, blood, clot and debris.
• Use a brush with stiff bristles, friction aids the
removal of organisms and debris in difficult to reach
areas
CLEANING CONTD
• Contaminated materials are easily dislodged using
friction.
• Rinse object in warm water
• Dry properly and ensure that objects are not wet
• Prepare the object for the best method of
disinfection or sterilization.
• Discard gloves, wash properly the brush and sink
used for the cleaning and keep for next use
ASCEPTIC (STERILE)
TECHNIQUE
STERILE TECHNIQUE
• Sterile technique or surgical asepsis refers to
practices that make objects & environment free from
all micro-organisms, it includes practices that
destroy all micro-organisms and spores they help to
ensure that contamination with micro-organism &
spores are prevented throughout a surgical
procedure involving sterile areas of the body.
• Sterile technique is practiced in operating rooms &
special diagnostic areas; it is also employed for
many procedures in the general care areas such as
administering injections, ivs, wound dressing etc
PRINCIPLES OF STERILE TECHNIQUE
• All articles to be used in sterile procedure must be properly
sterilized
• Sterile objects become unsterile when touched by unsterile
objects
• If in doubt about sterility of any item, consider as not sterile
• Non sterile person must avoid reaching over a sterile field &
vice versa.
• Tables, trolleys, trays are sterile only at table, trolley & tray
level
• Never turn your back on a sterile field
• The skin cannot be sterilised and is unsterile
• Fluid flow in the direction of gravity. Always hold wet
forceps with the tip below the handle
• The edges of anything that enclosed sterile contents are
considered unsterile
• A sterile field is continually kept in view
• Sterile person keep well within sterile areas and vice-versa
• Sterile objects can become unsterile by prolonged exposure
to airborne microorganism hence a sterile field is created as
close as possible to the time of use
• Hold sterile objects at the level of the waist, object above or
below are regarded as unsterile.
• Sterile persons keep well within sterile area to a minimum
• Moisture or wetness causes contamination hence damp or
wet packs especially if using an autoclaving method is
considered not sterile
• No compromise with sterility, conscientiousness, alertness
STERILE CONSCIENCE
• Keywords in nursing practice is caring, conscience,
discipline and technique, optimum client care require an
inherent sterile conscience , self discipline & application of
the principles of sterile technique’.
• Florence Nightingale summarized in her words “the nurse
must keep a high sense of duty in her own mind, must aim
at perfection in her care & must be consistent always in
herself”.
• Sterile conscience is one’s inner voice for conscientious
practices of sterile technique at all times. This does not
permit a person to excuse an error but rather to readily
admit & rectify
• It becomes so much a part of the person that he/she
can see at a glance or instinctively know if a break
in technique or violation of principles occurs
• Conscience dictates that appropriate action be taken
whether the person is with others or alone, a surgical
conscience therefore is the foundation for practices
of strict sterile technique practice
• A very important aspect in assisting the development
of a surgical conscience in others is not to castigate
a person of an error but praise the person instead,
for admitting & to help him/her correct the violation,
fear of criticisms is the primary deterrent in
admission of fault. No one should question a break
in technique.
REFERENCES
• Potter , P. A., Perry, A. G., Stockert, P. A., Hall, A. M.
(8th edition) Fundamentals of Nursing. Elsevier
Mosby, Missouri
• Berman, A. Synder, S. J., Kozier, B., Erb, G. (8th
edition) Kozier & Erb’s Fundamentals of Nursing
Concepts, Process, and Practice. Pearson Prentice
Hall, New Jersey
• Park, K. (18th ediition) Park’s textbook of preventive
and social medicine. Banarsidas Bhanot Publishers,
India.
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