it contains introduction about sterilization and disinfection with history and emphasis on chemical sterilization

1. Presented By- Yash Sukhwani
MSc. Previous Microbiology

2. CONTENT
• HISTORY
• TERMINOLOGIES
• INTRODUCTION
• METHODS OF STERILIZATION
• CHEMICAL METHOD

3. HISTORY
1. Oliver Wendal Holmes(1843) and Ignaz
Semmelweis(1846) concluded that puerperal sepsis was
transmitted by contaminated hands of Obstetricians, nurses,
medical students.
2. Can be prevented by washing hands in aseptic solution.

4. LOUIS PASTEUR(1822-1895)
1. Father of modern Microbiology.
2. Proposed GERM THEORY
3. In the course of these studies,
he introduced techniques
of sterilization and developed the
steam sterilizer, hot air oven and
autoclave.
4.Pasteurization.

5. JOSEPH LISTER
1. Father of Antiseptic Surgery.
2. In 1866, Lister suggested antiseptic
surgery which involved the use of CARBOLIC ACID.
3. Pronounced drop in mortality and morbidity observed.
Marked the Beginning of Modern aseptic conditions from the
era of Laudable pus.

6. JOHN TYNDAL (19th century)
1. Tyndallisation (Intermittent sterilization).
2.Student of Pasteur.
3. Tyndallisation essentially consists of boiling
the substance at 100°c for 15minutes for three
days in a row.
4.Used for media containing sugars and gelatin.
5.It is generally effective, but its reliability is not
considered 100% certified.

7. TERMINOLOGY
TERM DEFINITION

8. INTRODUCTION
The process of sterilization is used
• In microbiology for preventing contamination by extraneous
organisms.
•In surgery for maintaining asepsis
•In food and drug manufacture for ensuring safety from
contaminating organisms, and in many other situations.
The methods of sterilization employed depend on
•The purpose for which it is carried out
•The material which has to be sterilized and
•The nature of the microorganisms that are to be removed or
destroyed.

10. CHEMICAL AGENTS
 Alcohols – ethyl, isopropyl, trichlorobutanol
 Aldehydes – formaldehyde,
glutaraldehyde
 Dyes
 Halogens
 Phenols
 Surface active agents
 Metallic salts
 Gases – ethylene oxide, formaldehyde,
betapropiolactone

11. IDEAL CHEMICAL DISNIFECTANT
An ideal chemical antiseptic or disinfectant should have the
following properties:
Wide spectrum of activity
 Active in the presence of organic matter
 Effective in acid as well as alkaline media
 Speedy action
 High penetrating power
 Stable
 Compatible with other antiseptics and disinfectants
 Not corrode metals
 Not cause local irritation or sensitization
 Not interfere with healing
 Not be toxic if absorbed into circulation
 Cheap and easily available
 Safe and easy to use

12. MODES OF ACTION OF CHEMICAL
DISINFECTANTS
Protein coagulation
 Disruption of cell membrane resulting in
exposure, damage or loss of the contents.
 Removal of free sulphydryl groups essential for the
functioning of the enzymes.
 Substrate competition – a compound resembling the
essential substrate of the enzyme diverts or misleads the
enzymes necessary for the metabolism of the cell and
causes cell death.

13. ALCOHOLS
Ethanol (80% v/v ethyl alcohol) or
2-propanol (60-70% v/v isopropyl
alcohol) solutions are used to disinfect skin
and decontaminate clean surfaces.
Spectrum: Effective against fungi,
vegetative bacteria, Mycobacterium species
and some lipid-containing viruses.
Limitation: Not effective against
spores.
Concentration: Most effective at 70%
in water.
Caution:Do not use near flames
due to flammability.
May swell rubber or harden plastics.

14. ALDEHYDES
FORMALDELYDE: Precautions are required when
handling formaldehyde
Formalin is 37% w/v formaldehyde gas in water.
 Spectrum: Active against most microorganisms.
 Bactericidal, sporicidal, virucidal.
 13% v/v formalin is a good decontaminant (but has an
irritating odour).
8% v/v formalin in 80% v/v alcohol is effective
against
vegetative bacteria, spores and viruses.
 Does not corrode stainless steel.

15. Uses:
 Formaldehyde is used to preserve anatomical
specimens, and for destroying anthrax spores in hair
and wool.
10% formalin containing 0.5% sodium tetraborate is used
to sterilize clean metal instruments.
Formaldehyde gas is used to sterilize instruments, heat
sensitive catheters and for fumigation of wards, sick
rooms and laboratories.
It can also be used for clothing, bedding, furniture and
books.
To disinfect equipment such as centrifuges or biosafety
cabinets.

16. GLUTARALDEHYDE:
Concentration: Glutaraldehyde is commercially available as 2% w/v
aqueous solution which must be made alkaline to "activate" (e.g. by
addition of 0.3% sodium bicarbonate).
A 2% glutaraldehyde solution, for at least 10 hours, can be used to
sterilize heat labile items.
Spectrum: Active against vegetative bacteria, spores, fungi and
many viruses.
Note: Also available in stable glycocomplexed form which does not
require addition of alkaline buffer.
Use: for instruments such as
cystoscopes, bronchoscopes, corrugated rubber anesthetic
tubes, face masks, endotracheal tubes, metal
instruments, polythene tubing.

17. Caution: Glutaraldehyde is known to cause dermatitis and
asthma. Less irritating than formaldehyde.
Glutaraldehyde should not be used in an area with
little or no ventilation.
Eye protection, a plastic apron, and gloves must be
Worn
 Should be stored away from heat sources and in
containers with close-fitting lids.
The length of time that glutaraldehyde solutions can
be used varies but they are usually good for up to 14
days.
Solutions should be replaced any time they become
cloudy.

18. Glutaraldehyde
Advantages
Numerous use studies published
Relatively inexpensive
Excellent materials compatibility
Disadvantages:
Pungent and irritating odor
Relatively slow mycobactericidal
activity
Coagulate blood and fix tissues to
surfaces

19. CHLORINE COMPOUNDS
Generally used in the form of sodium hypochlorite.
Effective against a wide variety of microorganisms
(vegetative bacteria and viruses). Preferred disinfectant
for HIV and hepatitis viruses.
Concentration: Use at 0.1% as a general disinfectant.
Effective between a pH range of 6-8.
 Limitations:
 Less suitable in the presence of organic matter (such as blood).
Concentration must be increased to retain action (0.5%).
Strength decreases on standing (make fresh solutions daily).
High concentrations corrode metal surfaces, and bleach and
damage fabrics.

20. HYPOCHLORITE:
These are inexpensive, broad spectrum chlorine releasing
disinfectants of choice against viruses, including hepatitis
B virus.
 Aqueous solution of sodium hypochlorite (5.25%) is
called household bleach.
 It is used in a concentration of 0.2-1% depending upon
the circumstances.
 Caution: hypochlorite's are inactivated by organic
matter. They corrode metals, hence contact of the
chemical with the metallic instruments and equipment
must be avoided.

21.  In case of heavy spoilage
e.g. blood spillage, a
concentration of 10000 ppm
(1:5 dilution of
household bleach) of available
chlorine is recommended.
 Uses: it has great
widespread use as a
laboratory disinfectant
on surfaces of bench and in
discard spots.

22. CHLORHEXIDINE (hibitane)
 Chlorhexidine as chlorhexidine gluconate is dissolved in 70% alcohol.
 Effective against Gram-positive organisms and HIV.
 Active in ph range 5.5 - 8.0.
 Limitation: Not recommended as a general disinfectant.
 Not active against sporulating bacteria or non-lipid containing
viruses.
 Incompatible with soap and anionic detergents.
 Use: savlon (chlorhexidine+cetrimide) is widely used in
burns, wounds, as bladder irrigant, for surgical
instruments and pre-operative disinfection of skin.
 Use as antiseptic. Apply alcoholic chlorhexidine to the
skin in the event of accidental contamination.

23. HYDROGEN PEROXIDE
 A concentration of 3% w/v generally used for disinfection.
 Active against a range of microorganisms.
 Fungi, spores and enteric viruses require higher concentration.
 No toxic end-products of decomposition.
 Caution: Do not use on aluminium, copper, zinc
or
brass.
 Mechanism: H2O2 on decomposition liberates
free hydroxyl radical which is the active ingredient in
the process.
 Use: H2O2 is applied to disinfect plastic
implants, contact lenses, and surgical
prostheses.

24. PHENOLICS
 Synthetic phenolic (clear soluble fluids) can be used as
general disinfectants in the laboratory.
 Spectrum: Active against bacteria and lipid-containing
viruses.
 Not active against spores and non lipid- containing viruses.
 Active in presence of organic matter.
 Use: for disinfecting floors, walls, benches and other
furniture.
 Cresols: (methyl phenols, lysol)
 Limitation: toxic to skin and tissues.
 Use: mainly used for preliminary sterilization of
infected glassware's in laboratory, disinfection of
excreta, cleaning floors of wards and operation room in
hospital.
 Chloroxylenol (dimethyl phenol) is active ingredient of
Dettol.

25.  Hexachlorophane: it is bacteriostatic at very high dilutions
and used in soap and powder form. It is more effective against gram
positive than gram negative bacteria and is applied on skin as
prophylaxis against staphylococcal infection.
 Chlorhexidine: mentioned previously.
QUATERNARY AMMONIUM COMPOUNDS
 Quaternary ammonium compounds are positively charged
(cationic) surface-active disinfectants.
 Effective against Gram-positive bacteria and lipid containing
viruses.
 Not recommended as general disinfectants (they have a narrow
antibacterial spectrum).
 Inactivated by proteins, soap and anionic detergents.
 E.g.. Benzalkonium chloride, alkyldimethylbenzyl ammonium
chloride, and cetylpyridinium chloride.
 Used for cleaning of floors of hospitals.

26. ETHYLENE OXIDE
 It is an alkylating agent.
 Exerts lethal effect on proteins of bacteria.
 It is gas at ordinary room temperature and active against all types
of bacteria and spores.
 It has got a good degree of penetration power, even through
plastics.
ETO Machine
 Uses: Plastic goods, polythene tube,
artery and bone grafts, cystoscopes,
vaccines and culture media can be sterilized
by ethylene oxide.
 These objects are kept in a cabinet from
which air is
removed by a vacuum pump and then a mixture
of ethylene oxide and carbon dioxide is
introduced in the cabinet.