Sterilization and disinfection

Sachin Chauhan
sachu.chauhan@gmail.com

In mid 1800s Lister developed
Aseptic techniques to prevent
contamination of surgical
wounds. Prior to this
development:
•Nosocomial infections caused
death in 10% of surgeries.
•Up to 25% mothers delivering
in hospitals died due to
infection.
Sachin Chauhan

INTRODUCTION
• Microorganisms are the agents of
contamination, infection, and decay.
• Hence it becomes necessary to remove
them from materials and areas.
• Early civilization practiced salting,
smoking, pickling (Preserving) and
exposure to sunlight .Sachin Chauhan

DISINFECTION & STERILIZATION
STERILIZATION
Process of complete
destruction of all
microbes or micro-
organisms & their
bacterial endospores /
spores on a substance
by exposure to
physical or chemical
agents.
DISINFECTION
Process of reducing or
removing microbes or
micro-organisms
except bacterial
endospores but kills
vegetative forms of
bacteria.
Sachin Chauhan

Disinfectant - Chemicals used in disinfection are called disinfectants. Should be applied to
inanimate (lifeless) objects.
Decontamination is the process of removal of contaminating pathogenic microorganisms
from the articles by a process of sterilization or disinfection.
Antibiotics are substances produced by one microbe that inhibits or kills another microbe.
Sanitization is the process of chemical or mechanical cleansing. It reduces microbes on
eating utensils to safe, acceptable levels for public health.
Asepsis is the techniques (such as usage of gloves, air filters, uv rays etc) to achieve microbe-
free environment.
Antiseptic is the use of chemicals (antiseptics) to make skin or mucus membranes devoid of
pathogenic microorganisms. applied to living tissue, Some can be used as both.
Bacteriostatic is a condition where the multiplication of the bacteria is inhibited without
killing them.
Bactericidal is that chemical that can kill or inactivate bacteria.
Sporicide: An agent that kills spores.
TERMINOLOGY
Sachin Chauhan

Types of Disinfection
1) Concurrent Disinfection:
Immediate process of removing microorganisms. Eg. Linen
contaminated with blood, stool, urine, vomitus etc.
2) Terminal Disinfection:
Removal of microorganisms from contaminated objects at
convenient time. Eg. Bed, locker, mattress, IV stand, suction
& BP apparatus etc.
3) Prophylactic Disinfection:
As a preventive measure to prevent the spread of infection.
Eg. Boiling of water, pasteurization of milk, hand washing,
chlorination of water etc.
Sachin Chauhan

Levels of disinfection
• High-level disinfection: can be expected to destroy all
microorganisms, with the exception of large numbers
of bacterial spores.
• Intermediate disinfection: inactivates Mycobacterium
tuberculosis, vegetative bacteria, most viruses, and
most fungi; does not necessarily kill bacterial spores.
• Low-level disinfection: can kill most bacteria, some
viruses, and some fungi; cannot be relied on to kill
resistant microorganisms such as tubercle bacilli or
bacterial spores. Sachin Chauhan

Classification
Category Description Requirement
Critical Enters sterile body
cavity
Sterile
Semi-critical Contacts mucous
membranes, non-intact
skin
High level
disinfection
Non-critical Contacts intact skin Low level
disinfection
Sachin Chauhan

2)Vibration(D) 4)Filtration(D) 5)Cold/Freezing(D) 1)Liquid(D/S) 2)Solid(D) 3)Gas(S)
Candlefilters
Asbestosfilters
Sinteredglassfilter 1)Alcohols 1)BleachingPowder 1)EthylenOxide10-15%
Ionizing(S) Non-Ionizing(D) Membranefilters 2)Aldehydes 2)Formaldehyde
1)Electromagnetic 1)UltraViolet Rays 3)Phenolics
2)Cathode 4)Halogens
3)GammaRays
5)SurfaceActiveAgents
&MetalicSalts
6)Dyes-Aniline&Acridine
7)Blanisol-Pur1000ml(1
alkyldimethylbenzyl
ammoniumchloride-SDI
&Instrument Cleanser
8)Aldasan2000(Surface
disinfectants)-
Formaldehyde9.8gm&
Glutaral9.9gm 4)Plasma
5)Betapropiolactone
METHODSOFDISINFECTION/STERILIZATION
3)Radiation
ChemicalPhysical
3)EcoShield(Hydrogen
Peroxide11%with
DilutedSilvernitrate
0.01%)-usedfor
fumigationof
OT/ICU/BB/OPD/Clinic/L
ab
MoistHeat
1)BurnorRedHeat (D/S)
2)Flaming(D)
3)Ironing(D)
4)Hot AirOven(D/S)
1)Below100o
C(Pasteurization@60-72o
C)(D)
2)At 100o
C(Boiling)–15to20minutes(D)
3)Above100o
C(Steaming)@lowpressure(D)
4)Above100
o
C(Steaming)@lowpressurewithFormaldehyde(S)
5)Incineration(S)
6)InfraRedConveyerOven(S)
DryHeat
Natural (D)
SunLight
5)Above100o
C(Steaming)@highpressure(S)
Air 1)Heat/Temperature
Sachin Chauhan

Methods of
Disinfection/Sterilization
(1) Natural (D)
a) Sun Light
b) Air
(2) Physical (by temperature)
A. Dry Heat
i) Burn or Red Heat (D/S)
ii) Flaming (D)
iii) Ironing (D)
iv) Hot Air Oven (D/S)
v) Incineration (S)
vi) Infra Red Conveyor Oven (S)
Sachin Chauhan

Methods of
B. Moist Heat
i) Below 100o
C (Pasteurization @ 60 -72o C) (D)
ii) At 100o
C (Boiling) – 15 to 20 minutes (D)
iii) Above 100o
C (Steaming) @ low pressure (D)
iv) Above 100o
C (Steaming) @ low pressure with Formaldehyde (S)
v) Above 100o
C (Steaming) @ high pressure (S)
C) Vibration (D)
D) Radiation
i) Ionizing (S): Electromagnetic, Cathode & Gamma Rays
ii) Non – Ionizing (D): UV Rays
E) Filtration (D)
i) Candle filters
ii) Asbestos filters
iii) Sintered glass filter
iv) Membrane filters
Sachin Chauhan

Methods of
F) Cold or Freezing (D)
(3) Chemical Method
i) Liquid (D/S)
• Alcohols – ethyl alcohol & isopropyl alcohol
• Aldehydes – Formaldehyde & Glutraldehyde
• Phenolics – phenol (Carbolic acid)
• Halogens – Iodine, Hypochlorite, Bleaching powder
• Acids – Acetic & Boric Acid
• Surface Active Agents & Metalic Salts
• Dyes - Aniline & Acridine
• Blanisol - Pur 1000ml (1 alkyl dimethylbenzyl ammonium chloride - SDI &
Instrument Cleanser
• Aldasan 2000 (Surface disinfectants) - Formaldehyde 9.8gm & Glutaral
9.9gm Sachin Chauhan

Methods of
ii) Solid (D)
• Bleaching Powder
iii) Gas (S)
• Ethylen Oxide 10 - 15%
• Formaldehyde
• Eco Shield (Hydrogen Peroxide 11% with Diluted Silver nitrate 0.01%) - used
for fumigation of OT/ICU/BB/OPD/Clinic/Lab
• Plasma
• Betapropiolactone
Sachin Chauhan

Natural Methods
Sachin Chauhan

Natural Methods of
Sunlight:
The microbicidal activity of sunlight is mainly due to the presence
of ultra violet rays in it. This method used to disinfect hospital
furniture's like Chair, Tables, Locker, Coat, Mattresses. It can be
done every 15 days to 2 months by keeping the things for 3 hours
at least.
Air:
It is an natural disinfectant. It will disinfect the room by keeping
them well & cross ventilated. The windows & doors should be kept
open for enough light & air.
Sachin Chauhan

Physical Methods
Sachin Chauhan

Action of Dry Heat:
Dry heat acts by protein denaturation, damage the toxic
effects of elevated levels of electrolytes.
Action of Moist Heat:
The moist heat acts by coagulation and denaturation of
proteins. Moist heat is superior to dry heat in action.
Temperature required to kill microbe by dry heat is more than
the moist heat.
Physical Methods of
Sachin Chauhan

1) Burn or Red heat (D/S):
Articles such as bacteriological loops, straight wires, tips of forceps
are sterilized by holding them in Bunsen flame till they become red hot and
article like kidney tray, bowl, sputum mug are sterilized by pouring spirit &
making fire. This is a simple method for effective sterilization of such
articles, but is limited to those articles that can be heated to redness in flame.
2) Flaming(D):
This is a method of passing the article over a Bunsen flame, but not
heating it to redness. Articles such as scalpels, mouth of test tubes, flasks, glass
slides and cover slips are passed through the flame a few times. Even though
most vegetative cells are killed, there is no guarantee that spores too would die
on such short exposure.
This method too is limited to those articles that can be exposed to
flame. Cracking of the glassware may occur.
Dry Heat
Sachin Chauhan

3) Ironing (D):
it is an old method and no more in use. By this method we can
disinfect the bandages, OT clothes, draping clothes and other
linen materials.
Dry Heat
Sachin Chauhan

4) Hot air oven (D/S):
This method was introduced by Louis Pasteur.
Articles to be sterilized are exposed to high
temperature (160o C) for duration of one hour in an
electrically heated oven. Since air is poor conductor of
heat, even distribution of heat throughout the chamber
is achieved by a fan. The heat is transferred to the article
by radiation, conduction and convection. The oven
should be fitted with a thermostat control, temperature
indicator, meshed shelves and must have adequate
insulation.
Dry Heat
Sachin Chauhan

Sterilisation By Dry Heat:
Hot Air Oven
• Kills by oxidation effects
•The oven utilizes dry heat to
sterilize articles
• Operated between 50oC to
250/300oC.
•A holding period of 160oC for
1 hr is desirable.
• There is a thermostat
controlling the temperature.
•Double walled insulation
keeps the heat in and
conserves energy,
Dry Heat
Sachin Chauhan

5) Incineration (S):
This is a method of destroying contaminated material by
burning them in incinerator. Articles such as soiled dressings;
animal bodies, pathological material and bedding etc should be
subjected to incineration.
This technique results in the loss of the article, hence is
suitable only for those articles that have to be disposed.
Burning of polystyrene materials emits dense smoke, and hence
they should not be incinerated.
Dry Heat
Sachin Chauhan

5) Infra Red Conveyor Oven (S):
Similar to other electrical conveyor ovens, the infra red conveyor
oven utilizes short wave infra red lamp element to achieve
maximum heat.
Specification :-
• It is similar to Electrical belt Conveyor Oven but it has infrared
heating elements instead of other heating media.
• Temperature control: Automatic-Electronic
• Increases Production.
• Better quality of Product.
• Less process time.
• Less electric consumption as compared to
• other convection belt conveyor ovens
Dry Heat
Sachin Chauhan

Infra Red Conveyor Oven
Sachin Chauhan

1) Pasteurization (D):
Process of killing of pathogens in the milk but does not sterilize it .
Milk is heated at 63oC for 30 mins.
(HOLDER METHOD)
At 72oC for 15-20 Sec. Rapid cooling to 13oC
(FLASH PROCESS)
Moist Heat
Below 100o C
Sachin Chauhan

2) Hot Water Bath (D):
• To inactivate non sporing bacteria for the preparation of
vaccines - Special vaccine bath at 60oC for one hour is
used
• Serum or body fluids containing coagulable proteins can
be sterilized by heating for 1 hr at 56oC in a water bath
for several successive days.
Moist Heat
Below 100o C
Sachin Chauhan

Water Bath
Sachin Chauhan

3) Inspissator (D):
Sterilizes by heating at 80-85oC for half an hour
for 3 successive days
Used to sterilize media such as Lowenstein-Jensen
& Loefller’s serum
Moist Heat
Below 100o C
Sachin Chauhan

Inspissator
Sachin Chauhan

2) Boiling(D):
Kills vegetative forms of bacterial pathogens.
Hepatitis virus: Can survive up to 30 minutes of boiling.
Endospores: Can survive up to 20 hours or more of boiling
Moist Heat
At 100o C
Sachin Chauhan

3) Steaming at Low Atmospheric Pressure (D):
Steam is generated using a steamer (Koch/ Arnold)
Consists of a Tin cabinet Has a conical lid to enable the drainage of condensed
steam Perforated tray above ensures materials are surrounded by steam.
For routine sterilization exposure of 90 mins is used.
4) Steaming at Low Pressure with Formaldehyde (S):
Instruments like scopes, plastic & anesthetic equipment's should be sterilized
by steaming at low pressure with formaldehyde.
The drawback of this method is the cycle time is about 2 hours at 80o
C & it
irritates the living tissues, if formaldehyde remains in an articles.
Moist Heat
Above 100o C
Sachin Chauhan

Steaming at Low or Atmospheric Pressure
Sachin Chauhan

5) Steaming at High Pressure - Autoclave (S):
Works on the principle of Steam under pressure
Invented by Charles Chamberland in 1879.
Autoclave machine is made up of metal body & consists of a vertical or a
horizontal cylinder.
One end has an opening which is meant for keeping materials to be
sterilised.
The lid is provided with a Pressure gauge, to measure the pressure
A safety valve is present to permit the escape of steam from the
chamber
Articles to be sterilised are placed in the basket provided.
Sterilisation is carried out under pressure at 121º for 15 mnts.
Moist Heat
Above 100o C
Sachin Chauhan

Steaming at High Pressure - AutoclaveSachin Chauhan

ULTRASONIC AND SONIC VIBRATION
Bactericidal
Microorganisms vary in their sensitivity, hence no practical value
in sterilisation and disinfection.
Vibration (D)
Sachin Chauhan

1) Non – Ionizing (D):
Absorbed as heat
Can be considered as hot air sterilisation
Used in rapid mass sterilisation of pre packed Syringes and
catheters
Eg: UV rays & Infrared Rays
Radiation
Sachin Chauhan

ICU – ISOLATION ROOM
SINGLE CLOSED CUBICLE
CASES – OPEN TB , ANTHRAX, MRSA etc…
UV LIGHT FOR DISINFECTION
Sachin Chauhan

2) Ionizing (S):
Electromagnetic, Cathode, X- rays, gamma rays & cosmic rays.
High penetrative power
No appreciable increase in the temperature – COLD
STERILISATION
Sterilise plastics Syringes, catheters, grease fabrics metal foils
Radiation
Sachin Chauhan

Filtration helps to remove bacteria from heat labile liquids such as
sera and solutions of sugar, Antibiotics.
The following filters are used
1. Candle filters
2. Asbestos filters
3. Sintered glass filter
4. Membrane filters
Filtration (D)
Sachin Chauhan

CANDLE FILTERS
• Widely used for purification of water
Two types
(a) Unglazed ceramic filter – Chamberland
filter
(b) Diatomaceous earth filters – Berkefeld
filter
Sachin Chauhan

CANDLE FILTERSachin Chauhan

ASBESTOS FILTER
• Disposable single use discs
• High adsorbing tendency
• Carcinogenic
Eg: Seitz filter
Sachin Chauhan

SEITZ FILTER
ASBESTOS DISCSSachin Chauhan

SINTERED GLASS FILTER
• Prepared by heat fusing powdered glass
particles of graded size
• Cleaned easily, brittle, expensive.
Sachin Chauhan

SINTERED GLASS FILTERSachin Chauhan

MEMBRANE FILTERS
• Made of cellulose esters or other
polymers
Uses
• Water purification & analysis
• Sterilization & sterility testing
• Preparation of solutions for parenteral
use Sachin Chauhan

MEMBRANE FILTER
Sachin Chauhan

In this method temperature should be kept at -4O
C which stops
the growth of micro-organism but this process will not able to kill
them. For eg. Refrigerators
Cold/Freezing (D)
Sachin Chauhan

Chemical Methods
Sachin Chauhan

Chemical Methods of
1) Liquid
2) Gas
3) Solid
Sachin Chauhan

Specific Chemical
Antimicrobial Agents
• Halogens: Hypochlorous acid Chlorine (Cl),Iodine (I),
Bromine (Br), Chloramine
• Alcohols: denature proteins, skin antiseptics
• Phenols: disrupt cell membranes
• Oxidizing Agents:H2O2 disenfectant
• Alkylating Agents: disrupt nucleic acids and protein
structures, may cause cancer, formaldehyde, ethylene
oxide, glutaraldehyde
• Dyes: acridine and methylene blue, crystal violet
• Other Agents: plant oils for thyme and clove, nitrates,
sulfites, sodium nitrate ( p 338)Sachin Chauhan

Chemical Methods
(Liquid)
Sachin Chauhan

Chemical agents act by
• Protein coagulation
• Disruption of the cell membrane
• Removal of Sulphydryl groups
• Substrate competition
Sachin Chauhan

1) ALCOHOLS
• Ethanol /Isopropyl alcohol are frequently
used
• No action on spores
• Concentration recommended 60-90% in
water
Uses
• Disinfection of clinical thermometer.
• Disinfection of the skin – Venupuncture
Sachin Chauhan

2) ALDEHYDES
• Formaldehyde & Glutaraldehyde are
frequently used
• Formaldehyde is bactericidal, sporicidal &
has a lethal effect on viruses.
• Glutaraldehyde is effective against
Tubercle bacilli, fungi and viruses
Sachin Chauhan

USES
FORMALDEHYDE
• To preserve anatomical specimens
• Destroying Anthrax spores in hair and wool
• 10% Formalin+0.5% Sodium tetra borate is used to
sterilise metal instruments
GLUTARALDEHYDE
• Used to treat corrugated rubber anesthetic tubes,
Face masks, Plastic endotracheal tubes, Metal
instruments and polythene tubingSachin Chauhan

2% GLUTARLDEHYDE
Sterilization Disinfection
8-10 Hrs used for :- Pneumatic
circuits. i.e.- ventilator tubing
O2 masks ventury devices
nebulizer chamber
15-30 Mts used for dis
infecting endoscopes
Respiratory tubing's
Sachin Chauhan

PHENOLS
• Obtained by distillation of coal tar
• Phenols are powerful microbicidal
substances
• Phenolic derivatives have been widely
used as disinfectants for various purposes
in hospitals
• Eg: Lysol, cresol
Sachin Chauhan

USES
• Various combinations are used in the
control of pyogenic cocci in surgical &
neonatal units in hospitals.
• Aqueous solutions are used in treatment
of wounds
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LINEN
SOAKED IN 7% LYSOL
Sachin Chauhan

SUCTION TRAYS
o TO BE CHANGED EVERYDAY
o SUCTION CUPS
-CHANGED AFTER EACH USE
- IMMERSED IN 7% LYSOL FOR 1Hr
- WASHED WITH SOAP &WATER
- SENT FOR AUTOCLAVING
Sachin Chauhan

HALOGENS
• Iodine in aqueous and alcoholic solution
has been used widely as a skin
disinfectant
• Actively bactericidal with moderate
against spores
• Chlorine and its compounds have been
used as disinfectants in water supplies &
swimming pools
Sachin Chauhan

SURFACE ACTIVE AGENTS AND
METALLIC SALTS
Substances which reduce the surface tension –
Surface active agents
• Cations are widely used in the form of quaternary
ammonium compounds.
• Markedly bactericidal, active against Gram positive
organisms.
• No action on spores, tubercle bacilli, viruses
Sachin Chauhan

METALLIC SALTS
• The salts of silver, copper and mercury are
used as disinfectants.
• Act by coagulating proteins
• Marked bacteriostatic, weak bactericidal and
limited fungicidal activity
Sachin Chauhan

Blanisol – Pur 1000ml (Surface
Disinfectants)
Blanisol - Pur 1000ml (1 alkyl dimethylbenzyl ammonium
chloride - SDI & Instrument Cleanser
Sachin Chauhan

Blanisol – Pur 1000ml (Surface
Disinfectants)
Sachin Chauhan

Aldasan 2000
(Surface Disinfectants)
Aldasan 2000 (Surface disinfectants) – Formaldehyde
9.8gm & Glutaral 9.9gm
Sachin Chauhan

Aldasan 2000
(Surface Disinfectants)
Sachin Chauhan

Sterilium (80% Ethanol)
(Hand Disinfectants)
• The classic among rub-in hand disinfectants for hygienic and
surgical hand disinfection
• best peer-reviewed hand-disinfectant – quality since 1965
• possesses an excellent immediate effect
• provides very good residual effect
• excellent skin tolerability even with long-term use
• Areas of application
For hygienic and surgical rub-in hand disinfection – independent
of washbasin and water. For all areas that are relevant to
hygiene.
Sachin Chauhan

Sterilium
(Hand Disinfectants)
Sachin Chauhan

DYES
Two groups of dyes are used
Aniline dyes
Acridine dyes
Sachin Chauhan

ANILINE DYES
• Are Brilliant green, Malachite green &
Crystal violet
• Active against Gram positive bacteria
• No activity against tubercle bacilli
Sachin Chauhan

ACRIDINE DYES
• Acridine dyes in use are orange in colour
• Effective against Gram positive than Gram
negative
• Important dyes are Proflavine,
Acriflavine,Euflavine
Sachin Chauhan

Chemical Methods
(Gases)
Sachin Chauhan

GASES
Ethylene Oxide
–Colourless ,Highly penetrating gas
with a sweet ethereal smell.
–Effective against all types of
microorganisms including viruses
and spores
Sachin Chauhan

ETHYLENE OXIDE(EO)
Used for polythene and plastic items
E.g.:- Ambu bag, Baines circuit, Domes, Biopsy Needle,
Electric items, Rubber items
Pre-caution:-
Thorough cleanliness and dryness
Adequate aeration at least 12Hrs
Sachin Chauhan

USES
• Specially used for sterilising heart-lung
machines,respirators,sutures,dental
equipments, books and clothing.
• Also used to sterilise Glass, metal and
paper surfaces ,plastics, oil,some foods
and tobacco.
Sachin Chauhan

FORMALDEHYDE GAS
• Widely employed for fumigation of
operation theatres and other rooms
Sachin Chauhan

Eco Shield
Eco Shield (Hydrogen Peroxide 11% with
Diluted Silver nitrate 0.01%) - used for
fumigation of OT/ICU/BB/OPD/Clinic/Lab
Sachin Chauhan

BETA PROPIOLACTONE
• Used in fumigation
• For sterilisation 0.2% BPL is used
• Has a rapid biocidal activity
• Very effective against viruses
Sachin Chauhan

Plasma Sterilizer
Sachin Chauhan

The level of disinfection achieved depends on several factors:
• Contact Time & Temperature
• Items must be thoroughly cleaned before processing, because
organic material (e.g., blood and proteins) may contain high
concentrations of microorganisms. Also, such organic material
may inactivate chemical germicides and protect
microorganisms from the disinfection or sterilization process.
• Some disinfectants gradually loss their effectiveness after
diluting with water.
• Use of same solution for long time, loses their effectiveness.
Also it is prone to grow micro-organisms.
• This method is only used for non boilable, scopes & sharp
instruments.
POINTS TO REMEMBER FOR
CHEMICAL DISINFECTION
Sachin Chauhan

Actions
Spirit:
• General skin disinfectant constricts your skin,
preventing dirt and stain from infecting the skin.
• Also can be used as a rub to harden the skin of the
hands and feet.
• It prevents bleeding while giving injection due to
constriction of blood vessels.
Sachin Chauhan

Sterilization and disinfection

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