Download sterilization and disinfection

STERILIZATION AND ASEPSIS
INTRODUCTION:
Sterilization is defined as the process by which an
article, surface or medium is freed of all living
micro-organisms either in the vegetative or spore
state.
Disinfection means the destruction or removal of all
pathogenic organisms or organisms capable of
giving rise to infection
Anti-sepsis is used to indicate the prevention of
infection usually by inhibiting the growth of
bacteria in wounds or tissues
HISTORY OF ASEPSIS
• Hippocrates – cleanliness
• Semmelweis (1847) – washing hands prior to delivery reduced
puerperal fever
• Lister (1865) – influenced by louis pasteur suggested carbolic
acid as an antiseptic
• Lawson tait – antisepsis to asepsis, introduced principles and
practices of asepsis
• Ernst von Bergmann (1880) – introduced autoclave
CLASSIFICATION
•
PHYSICAL AGENTS:
1) SUNLIGHT
2) DRYING
3) DRY HEAT a) FLAMING b) INCINRATION c) HOT AIR
4) MOIST HEAT: PASTEURISATION,BOILING,STEAM UNDER NORMAL PRESSURE,
STEAM UNDER PRESSURE.
5) FILTRATION: CANDLES, ASBESTOS PACKS, MEMBRANES.
6) RADIATION
7) ULTRASONIC AND SONIC VIBRATIONS.
•
CHEMICAL AGENTS:
1) ALCOHOLS- ETHLY ISOPROPYL,TRICHLOROBUTANOL
2) ALDEHYDES- FORMALDEHYDE, GLUTARALDEHYDE.
3) DYES4)HALOGENS `
5) PHENOLS
6) SURFACE ACTIVE AGENTS
7) METTALIC SALTS
8) GASES- ETHYLENE OXIDE, FORMALDEHYDE, BET PROPIOLACTONE
PROPERTIES
An ideal antiseptic or disinfectant should:
1) Have a wide spectrum of activity and be effective against all micro
organisms
2) Be active in the presence of organic matter
3) Be effective in acid as well as alkaline media
4) Have speedy action
5) have high penetrating power
6) Be stable
7) Be compatible with other antiseptics and disinfectants
8) Not corrode metals
9) Not cause local irritation or sensitization
10) Not interfere with healing
11) Not to be toxic if absorbed into circulation
12) To be cheap and easily available
13) Be safe and easy to use
FACTORS THAT DETERMINE THE
POTENCY OF DISINFECTANTS
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Concentration of the substance
Time of action
pH of the medium
Temperature
Nature of the organism
Presence of extraneous material
MODES OF ACTION
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Protein coagulation
Disruption of cell membrane
Removal of the free sulphydryl groups
Substrate competition
4 Stages :•
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Pre-sterilization cleaning.
Packaging.
Sterilization methods.
Aseptic storage.
Physical Agents
SUNLIGHT
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Bactericidal activity
Under natural conditions
Action: primarily- UV rays
DRYING
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4/5th by wt bacterial cell-water
Drying-deleterious effect on bacteria
Unreliable & theoretical interest
spores are not effected
HEAT
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
Most reliable method
Factors influencing:
a. Nature of heat
b. Temperature & time
c. Number of microorganisms present
d. Characteristic of organisms
e. Type of material
DRY HEAT
Action

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Protein denaturation
Oxidative damage
Toxic effect of elevated levels of Electrolytes
1.Flaming:
Inoculating loops or wires, points of
forceps, searing spatulas under Bunsen flametill red hot
2. Incineration:
Destruction of materials –
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Soiled dressings
Animal carcasses
Bedding
Pathological materials
Plastics-PVC, polythene
Except polystyrene.
3. Hot Air Oven:
 Pastuer-1876
Holding period-160c-1hr
 Sterilizes-glassware,
forceps, scissors, scalpels,
all-glass syringes, swabs,
liquid paraffin,powders
 Control: Clostridium tetani
MOIST HEAT
Mechanism of action:Dry saturated steam
Meets cooler surface
Gets condensed into a packet
of water
Latent heat lib.
enzyme.
-1600ml steam at 100° C
At atmospheric pressure condenses
to 1ml H2O 518 cal heat.
. Denaturation
. Membrane damage.
. Chromosomal damage.
. Enzyme coagulation.
Types of moist heat• Below 100°C. (Pasteurization)
• At 100°C . ( Tyndallisation )
• Above 100°C . ( Under pressure )
• Below 100 °C ( Pasteurization)
2 Types•
Holder method : 63°C for 30 mins.
•
Flash process : 72°C for 20 sec…rapid cooling to 13°C.
•
Mycobacteria, brucellae & salmonellae……...
• Application:- OT table side or bed side sterilization.
- Vaccines of non-sporulating bacteria.
- Sterilization of L-J media & Loeffler’s serum.
Tyndallisation
• At 100°C:• Boiling…Vegetative bacteria killed immediately..sporing
bacteria…not a recommended procedure…as a disinfection..
• Used in cases where boiling is considered adequate..closed lid….1030 min.
• Principle90-100°C for 20 min on three successive days
Followed by incubation at 37°C in between.
MOIST HEAT
 Temperature <100c
 Pasteurization of milk:
holder method -63c-1/2hr
flash method -72c-15-20 sec
Cooling quickly -13c or lower
Temperature at 100c:
Boiling:


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vegetative bacteria-90-100c
hard water-not to be used
2%NaHCO3-increases boiling point
of water.
Steam at atmospheric pressure:100c
*
Koch or Arnold steamer used
* one exposure of 90min
*
Tyndallization/intermittent sterilization
*
Media containing sugars or gelatin100c for 20 min-3 days
AUTOCLAVE
STEAM UNDER PRESSURE:
* Principle: water boils when its vapour pressure equals that
of the surrounding atmosphere.
* saturated steam has penetrative power. when steam comes
in to contact with a cooler surface it condenses to water and
gives up its latent heat to that surface .
*The larger reduction in volume sucks in more steam to the
area and the process continues till the temperature of that
surface is raised to that of the steam. The condensed water
ensures moist conditions for killing the microbes present.
121°C (250°F)..15-20 min..15 lbs.
Dressings , instruments, laboratory ware, media and
pharmaceutical products can be sterilized. .
Several types of steam sterilizers are in use:
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Laboratory autoclaves
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Hospital dressing sterilizers
Bowland instrument steilizers, and
Rapid cooling sterlizers
(even the domestic pressure can be used as a
sterilizer).
Consideration during Autoclaving
1. Ensure complete air removal for temp to reach
121°C.
2. Ensure loose packing in the chamber.
3. Always remove chemicals and then place.
4. Tightly sealed materials may become
dangerously pressurized causing injury when
removed.
5. A routine autoclave maintenance program
recommended.
STERILISATION CONTROL
* For determining the efficacy of moist heat
sterilisation , spores of bacillus
stearothermophilus are used as the test
organism.
Chemical indicators, autoclave tapes
and thermocouples may also be used
instead.
Glass bead sterilizer
• Glass beads, molten metal and salt.
• Temp- 220°C, 10 sec.
• Use- endodontic files, burs..
• Disadv:- no uniform heat.
FILTRATION
To remove bacteria from heat labile liquids
-sera, sugar solutions & antibiotics.
Types:
a. candle filters:
i. unglazed ceramic filters
ii. Diatomaceous earth filters
b. Asbestos filters:
c. Sintered glass filters
d. Membrane filters
Types:
RADIATION
a. Non ionising :
Infrared radiation- prepacked
syringes & catheters
UV radiation-entry ways,
OT & lab
b. Ionsing radiation {cold sterilization} :
X-rays, gamma rays & cosmic rays
high penetrating power-lethal to DNA
sterilizes- plastics, syringes, swabs, catheters,
CHEMICAL AGENTS
Alcohols:
a) Ethyl alcohol (ethanol) and isopropyl alcohol
are the most frequently used.
mainly used as skin antiseptics and act by
denaturing the bacterial proteins. (but no actions
on spores and viruses).
b) Methyl alcohol is effective against fungal
spores and is used for treating cabinets and
incubators affected by them.
ALDEHYDES:
a) Formaldehyde in aqueous solutions, markedly
bactericidal and sporicidal- has a lethal effect on viruses.
10% formalin with ½ % sodium tetraborate is used to
sterilise clean metal instruments.
Formaldehyde gas is used for sterilising instruments and
heat sensitive catheters, also for fumigating wards, sick
rooms and labs
b) Glutaraldehyde is specially effective against tubercle
bacilli, fungi and viruses ( less toxic n irritant to the eyes
and the skin than formaldehyde.)
Corrugated rubber anaesthetic tubes and face masks,
plastic endotracheal tubes, metal instruments and
polythene tubing.
Dyes:
a) Aniline dyes and b) Acridines are used
extensively as skin and wound antiseptics
(bacteriostatics in high dilution but of low
bactericidal activity).. They are more active
against gram positive than gram negative
organisms. They have no activity against
tubercle bacilli.
Lethal effects on bacteria are due to their
reactions with the acid groups in the cell.
Halogens:
1) Iodine in aqueous and alcoholic solutions has
been used as a SKIN DISINFECTANT. Is an active
bactericidal agent with a moderate activity against spores, tubercle
bacillus and number of viruses. Compunds of iodine
( iodophores) are more active than aqueous or
alcoholic soln.
2) Chlorine and hypochlorites are markedly bactericidal.
They have a wide spectrum of activity against viruses.
* The organic chloramines are used as antiseptics for dressing
wounds.
PHENOLS:
Lister( father of antiseptic surgery) first introduced
their use in surgery.
The lethal effect phenols is due to their capacity to
cause cell membrane damage, releasing cell
contents and causing lysis.
phenols and their derivatives are widely used for
various purposes in hospitals & the
combinations( chlorophenols and
chloroxyphenols) are used in the control of
pyogenic cocci in surgical and neonatal units.
GASES:
Ethylene oxide: its action is due to its power of alkylating the amino,
carboxyl, hydroxyl and sulphydryl groups in the protein molecule
and also reacts with the DNA and RNA.
Effective against all types of microorganisms including viruses and
spores.
Specially used for sterilizing heart-lung machines, respirators, sutures,
dental equipments and clothing.
Formaldehyde gas: widely employed for fumigation of operation
theaters and other rooms.
BetaPropiolactone(BPL): (condensation product of ketane and
formaldehyde)
More effective than formaldehyde for fumigating purposes.
It has a rapid biocidal action but unfortunately has carcinogenic
activity.
It is capable of killing all micro organisms and is very active against
viruses.
Surface acing agents:
a)anionic, b)cationic, c)nonionic, d)amphoteric
The most important antibacterial agents are the cationic
surface active agents.
These act on the phosphate groups of the cell membrane
and also enter the cell.
Metallic salts:
salts of silver, copper, and mercury are used as
disinfectants.
Protein coagulants and have the capactiy combine with
free sulphydyrl groups of cell enzymes.
The organic compounds, thio mersal, phenyl mercury
nitrate and mercurochrome are less toxic and are used
as mild antiseptics and marked bacteriostatics, limited
fungicidal and weak bactericidal activity.
MATERIAL
METHOD
All suture materials (except
Catgut)
Catgut
Preservatives for gut sutures
Surgical needles and suture
materials in manufacturing
unit
Rubber gloves, surgical
instruments
Forceps, scalpel, scissors
Disposable syringes
Operation theatres
Autoclave , Glutaraldehyde
Ionising Radiation
Isopropyl Alcohol
Gamma radiation
Autoclave
Hot Air Oven
Ethylene oxide
Fumigation with
formaldehyde
UNIVERSAL PRECAUTIONS
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CONCEPT:
To address the inability of health care providers to specifically
identify all patients with communicable diseases.
THEORY:
protection of self , staff and patients from contamination by using
barrier techniques when treating all patients as if they all had a
communicable disease ensures that everyone is protected from those
who do have an infectious process.
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COMPONENTS:
All doctors and staff who come in contact with patients blood or secrtetions ,
whether directly or in aerosol form , wear barrier devices including face mask eye
protection and gloves
decontaminating or disposing of all surfaces that are exposed to patient blood
tissues and secretions .
avoidance of touching and thereby contaminating surfaces ( eg: dental record ,
telephone, etc.,) with contaminated gloves or instruments.
PERSONAL BARRIER PROTECTION
GLOVES:
•
All clinical personnel must wear treatment
gloves during all treatment procedures.
• After each appointment , or if leak is detected ,
remove gloves, wash hands and put on fresh gloves.
• Instead of attempting to wash gloved hands before
opening drawers or handling items adjacent to the
operatory, use tongs , a paper towel, or a food
handler’s over glove, to prevent contamination.
• All personnel with weeping or draining lesions that
could infect patients abstain from patient contact.
• Gloves that become penetrated or torn can
imbibe patient fluids and therefore should be
removed.
• Viruses have been found to penetrate not more
than one intact latex gloves out of hundred.
Double gloving prevents perforations of the
inner glove and therefore, adds protection.
• Latex gloves must have less than four percent
leak detectable water test. While handling sharp
instrument wear puncture resistant utility gloves.
• Nitrile latex gloves can be washed inside and
out, disinfected or steam autoclaved
PROTECTIVE MASKS AND HAIR PROTECTION.
• wear masks to protect against heavy spatter ,blood
droplets. Change the mask between every patient or
whenever it becomes visibly soiled or moist.
• masks with highest filtration are rectangular, folded
types used for surgeries.
• hair can trap heavy contamination hence should be
kept out of the treatment field by a protective head
cap.
PROTECTIVE OVER GARMENTS
• for protection of clothing and skin , sleeves
with knit cuffs that tuck under gloves are
preffered.
• Wearing contaminated garments home or out
of the clinical area should not occur.
• hot water up to 70 c or cool water containing
50 to 150ppm of chlorine provided by liquid
laundry bleach would provide more
antimicrobial action. Use of a hot air dryer and
/or ironing is also beneficial
SCRUB PROCEDURE
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The recommended scrub procedure for a particular operating
room is usually posted in the scrub area. The initial scrub
usually encompasses the following routine.
rinse hands and forearms with water, then wash with soap.
cleanse nails with an orange wood stick or nail cleanser
contained in scrub packs.
Start 10 minute scrub and work to an abundant lather, using
either brush or sponge. The palms, backs of hands, and fingers
are scrubbed first then the forearms. Scrub one hand and arm
and then the other.
when rinsing, raise both hands so that water will run down
and off at the elbows.
When the 10 minute scrub is finished , raise hands and prepare
to enter operating room.
STERILE TECHNIQUE:
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when the scrubbing is completed, keep the arms and hands
raised.
when the gown and gloves are on, do not drop hands below
waist level or raise above the head.
Remember the back of the operating gown is not sterile. Do
not reach behind anyone.
When passing another gowned person, pass back to back.
when standing at the table, keep hands on sterile drape that
covers the patient (do not exert pressure because this may
interfere with respiration).
Do not touch mask or cap. If adjustment is necessary, ask the
circulating nurse.
Do not break the scrub ( take off gloves, etc.) until surgery has
been completed.
PREPARATION FOR INTRAORAL
PROCEDURES
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Make sure that all anesthetic equipment is cleared from the
operative site.
Prepare the peri-oral regions first starting at the corner of the
mouth and working outward to the cheek , once at the
periphery, do not return to the starting point.
With a freshly dampened sponge, repeat this process on the
other side of the face.
the inside of the mouth may be cleansed. Although the mouth
is not a sterile area and cannot be sterilized, some surgeons
prefer at least to sponge out the mouth prior to surgery
When the preparatory procedure is completed, the circulating
nurse will take the cup and sponge stick
DRAPING THE PATIENT
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after the preparation is completed, the patient is
draped.
the simplest method of draping is the “ four towel
and thyroid drape” . Where thyroid drapes are not
available, a large body sheet may be used in
conjunction with a cystoscopy drape.
In the technique , the towels are applied first then the
body sheet, and finally the cysto sheet.
In both techniques , the only visible area left is the
operative site
HBV RISKS FOR CLINICAL PERSONNEL
DATA RELATED:
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Rate of cross infection is found to be 30%.
HBV is found in 1 of 100 to 500 persons in general
population.
Even only 1000³ virions per ml of blood of HBV is
capable of transmitting the disease
HBV is found to be resistant to dessication and
chemical disinfectants like alcohols , phenol, etc.,
Up to 90% of HIV infected patients have been infected
with HBV
Whether infected persons are symptomatic or not , they
can transmit HBV infection .
Mortality rates from HBV infection is 6.6 times to that of
HIV.
HBV is found in small concentrations in saliva and can be
transmitted by contamination of broken skin , mouth, or
eyes with blood contaminated saliva.
HIV RISK FOR CLINICAL PERSONNEL
DOCUMENTED DATA RELATED TO HIV :
Rate of cross infection is 0.3% .
1. unlike HBV , very low levels of HIV are found in
blood of infected patients.
2. in dried , infected blood 99% of HIV is found
inactivated in approx 90 minutes. But in wet
conditions virus may survive for two or more days.
3. HIV is killed by all methods of sterilization in less
than 2 minutes ( exception quarternary ammonium
compounds)
4. HIV can be transmitted by heavily splattered or
splashed blood contaminated fluids, but aerosols are
not found to transmit HBV or HIV .
5. Barrier techniques have great successful rates in
decreasing incidence of HIV infection.
PRECAUTIONS:
1.
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4.
Follow universal precautions.
Protect eyes , mucosa , skin and hands from splatter and direct
contact with blood and blood contaminated body fluids during
dental treatments of all patients.
Precautions to minimize risks of injuries with sharp
instruments.
Minimize aerosols to minimize risk of secondary transmissable
respiratory infections like tuberculosis and cytomegalovirus.
NEEDLE STICK INJURY PROTOCOL:
1) Significant exposures:
a) contaminated needlestick
b) puncture wound from a contaminated sharp
dental instrument.
c) contamination of any obviously open
wound or mucous membrane by saliva, blood or
a mixture of both.
2) Exposure to the patients blood or saliva on the
unbroken skin is not considered significant.
3) Protocol:
a) immediately clean the wound thoroughly
with soap and water.
b) have the sample of patients blood, drawn on
the same day and test it for HBV and HIV
c) the exposure recipient should also be tested
for anti HBV and anti body to HIV on the same
day of exposure.
POST EXPOSURE PROPHYLAXIS FOR HBV
Patients antigen status
1) HBsAg negative
2) HBsAg positive
recipient of exposure
1)HB vaccine, if not already
received
2a. Anti HBs positive recipient
no Rx
2b. HB vaccine recipient with
seroconversion no Rx necessary.
2c. HB vaccine without
seroconversion 1 additional dose of
vaccine
2d. Anti HBs –ve recipient:
HBIG starting within 48hrs after
exposure and HB vaccination started within
7 days.
POST EXPOSURE PROPHYLAXIS FOR HIV:
“No anti retro viral drug has been licensed”
These can be prescribed on an off label basis.
since their use for PEP is outside approved indications.
Recommended drugs- (emergency starter packs)
Zidovudine 250mg-300mg b.d + Lamivudine-150mg b.d.
+ Nelfinavir-1250mg b.d.(750mg tds)
other protease inhibitors:Ritonavir boosted Lopinavir
Saquinavir
Amprenavir
Duration: it should be started within 2-24hrs of exposure and not
beyond 48-72hrs. And should be continued upto 4weeks.
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