This document discusses the history and methods of disinfection and sterilization. It summarizes that Ignaz Semmelweis pioneered antiseptic procedures in 1847 by recommending chlorinated lime solutions for washing hands to prevent puerperal fever. Joseph Lister introduced carbolic acid to sterilize surgical instruments in 1865. Disinfection destroys pathogens but not all microbes like spores, while sterilization removes all microorganisms and spores. Common sterilization methods include heat, chemicals, radiation and filtration.
3. IGNAZ PHILIPP SEMMELWEIS
• early pioneer of antiseptic procedures
• "saviour of mothers“
• Puerperal fever was common in mid-19th-
century hospitals and often fatal.
Semmelweis proposed the practice of
washing hands with chlorinated lime
solutions (calcium hypochlorite) in 1847
while working in Vienna General Hospital .
IGNAZ PHILIPP SEMMELWEIS (1818-1865)
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4. JOSEPH LISTER
• Pioneer of antiseptic surgery.
• Lister successfully introduced carbolic acid
(now known as phenol) to sterilise surgical
instruments and to clean wounds in 1865.
JOSEPH LISTER (1827-1912)
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5. Disinfection -: Thermal or chemical destruction of pathogen and other type of
microorganisms.It destroys most recognized pathogenic microorganism but not
necessarily all microbial forms (e.g. bacterial spores).
Sterilization :- removal of all micro organisms and their spore.
Antiseptic :- the chemical substance used to remove microbes from skin, do not cause
any harm .
Disinfectant :- chemical agent ( sometimes physical) that destroys disease causing
pathogens or harmful micro organisms, might not kill bacterial spores. Applied to
inanimate objects.
6. Properties of an
ideal disinfectant
Broad
spectrum
odourless
Economical
Easy to use
Residual
effect
Environ
mentally
friendly
solubility
stability
Surface
compatibility
Non toxic
Fast acting
Properies of an ideal disinfectant
7. Precurrent
(prophylactic)
disinfection
• Pasteurization of
milk
• Disinfection of
water by chlorine.
• handwashing
Concurrent
disinfection
• Disinfection of
faeces ,vomit,
contaminated
linen, clothes ,
hands, dressings,
aprons, gloves
etc.
Terminal
disinfection
• Airing and
sunning of rooms
, furniture and
bedding.
Types of disinfection
9. Physical method
Dry heat
Red hot flaming Hot air
oven
incinerati
on
filteration radiation
Non
ionising
Ionising
radiatiion
Moist
heat
Below
100℃
At 100℃
Above
100℃
UV &
infrared
X-rays and
gamma rays
Oxidative
damage
10. Physical methods
Dry heat
a) Red hot
Red heat sterilization is the process of instant sterilization by holding the instruments in a Bunsen
flame till they become red hot. This method is based on dry heat sterilization is commonly used
for sterilization of instruments like inoculating loops, wires, and points of forceps.
b) Flaming
Glass slides ,scalpels and mouths of culture tubes are passed through Bunsen flame without
allowing them to become red hot.
11. c) Hot air oven
• Uses –
1. Glasswares like glass syringes ,
petridishes ,flasks ,pipettes and test
tubes.
2. Surgical instruments like scalpels
,scissor ,forceps etc
3. Chemicals like liquid paraffin, fats ,
sulphonamides etc.
• Sterilisation control –
a) Bacillus subtilis niger
b) Thermocouples
c) Browne’s tube
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12. Temperature and time in Hot Air Oven
• 160 ℃ for two hours (holding time) , or
• 170 ℃ for one hour , or
• 180℃ for 30 minutes .
The drawback of hot air is that it has no penetrating power , and is therefore not
suitable for disinfection of bulky articles such as mattresses. Also plastics , rubber
and other delicate substance are destroyed at such high temperature.
d)Incineration :-
• Infective material reduced to ashes by burning .
• Incinerator is used to deal with soiled dressings, animal carcasses , bedding and
pathological materials.
14. MOIST HEAT
AT A TEMPERATURE BELOW 100 ℃
a) Pasteurisation – two methods holder method ( 63 ℃ for 30 minutes) and flash method (72 ℃ for 20
seconds followed by cooling quickly to 13 ℃ or lower ) are used . All non- sporing pathogens such as
mycobacteria, brucellae and salmonella are killed except coxiella burnetti which being relatively heat
resistant may survive in holder method.
b) Inspissation - LJ medium and loeffler’s serum , are rendered sterile by heating at 80-85 ℃ temp for
half an hour daily for three consecutive days.
c) Vaccine bath – bacterial vaccines are sterilized in special vaccine baths at 60 ℃ for one hour.
d) Low temperature steam formaldehyde (LTSF) sterilization – steam at sub atmospheric pressure at
the temperature of 75 ℃ with formaldehyde vapour is used. Biological control bacillus
stearothermophillus.
15. AT A TEMPERATURE OF 100 ℃
a. Boiling – boiling for 10 to 30 minutes may kill most of the vegetative forms but not spores.
Boiling for 30 minutes is adequate to disinfect linen, utensils and bedpans.
b. Tyndallisation or intermittent sterilization – steam at 100 ℃ for 20 minutes on three
successive days is used. Used for sterilization of egg , serum or sugar containing media which get
damaged at high temperature of autoclave. Koch’s and Arnold’s steam sterilizer is commonly
used
AT ATEMPERATURE ABOVE 100 ℃
AUTOCLAVE
Sterilisation conditions;-
Temperature : 121 ℃
Chamber pressure :15 lb per square inch
Holding time :- 15 minutes
17. RADIATIONS
A) IONISING RADIATION
• X-rays , gamma rays and cosmic rays have high penetrating power .
• Gamma radiations from a cobalt-60 are commercially used for sterilization of
disposable items such as plastic syringes, swabs, culture plates , cannulas, catheters etc.
• This is known as cold sterilization .
• The advantages of this method include speed, high penetrating power ( it can sterilize
materials, through outer packages and wrappings)
• Bacillus pumilis has been used for testing the efficacy of ionizing radiations.
18. B) NON – IONISING RADIATIONS
• These include infrared and UV radiations.
• Infra red is used for rapid mass sterilisation of syringes and catheters.
• UV radiation with wavelength of 240 to 280 nm has marked bactericidal activity.
• Used for disinfecting enclosed areas such as bacteriological laboratory, inoculation
hoods, laminar flow and operation theatres.
• Vegetative bacteria are susceptive but not spores.
19. Filteration method
• Mainly used for heat labile liquid
• Types
1. Candle filter- purification of water for drinking.
2. Asbestos filter- single use disc and are carcinogenic
3. Sintered filter- expensive and easily brittle
4. Membrane filter – made up of cellulose ester . Mainly used in microbiology
and average pore diameter is 0.22 mm.used for preparation of solutions for
parental use.
5. Air filters- HEPA (high efficiency particulate air filters) air filters.
6. Syringe filters
20. Chemical
methods
Alcohols
Aldehydes
Phenols
Halogens and their
compounds
Quaternary ammonia
compounds
Oxidising agents
Metals as
microbicides
Vapour phase
disinfectant
A variety of chemical
agents are used as
antiseptics or
disinfectant.
High level disinfectants –
(cystoscope,endoscopes)
1. Glutaraldehyde
2. Hydrogen peroxide
3. Paracetic acid
4. Chlorine compounds
Intermediate level disinfection-
(laryngoscopes, fibreoptic
endoscopes)
1. Alcohols
2. Iodophores
3. Phenolic compounds
Low level disinfection-
(stethoscopes, ecg slectrodes.etc)
21. Chemical methods
1) Phenols and related compounds-
a) Phenol - Pure phenol is not an effective disinfectant. It is used as a standard to
compare the germicidal activity of disinfectants.
b) Crude phenol : It is a mixture of phenol and cresol.It is a dark oily liquid. Its
effect is greatly weakened by dilution.
c) Cresol - Cresol is an excellent coal-tar disinfectant. It is 3 to 10 times as powerful
as phenol. Cresol is best used in 5 to 10 per cent strength for disinfection of
faeces and urine. A 5 per cent solution may be prepared by adding 50 ml to one
litre of water.
22. d) Cresol emulsions : "saponified cresol".
Lysol, izal and cyllin are cresol emulsions. Lysol contains 50- 60 per cent cresol. Most commonly used for
sterilization of infected glasswares, cleaning floors, disinfection of excreta (2% solution.)
e) Chlorhexidine (hibitane)-:- : This is one of the most useful skin antiseptics. 0.5 per cent alcoholic or
aqueous solutions can be used as effective handlotions. Creams and lotions containing 1 per cent
chlorhexidine are recommended for burns and hand disinfection.
f) Dettol : Dettol (chloroxylenol) is a relatively non-toxic antiseptic and can be used safely in high
concentrations. It is more easily inactivated by organic matter. Dettol (5%) is suitable for disinfection of
instruments and plastic equipment; a contact of at least 15 minutes will be required for disinfection.
23. 2. Quaternary ammonia compounds
(1) Cetrimide : It is manufactured under the trade name "cetavlon ". It is actively
bactericidal against vegetative gram-positive organisms, but much less so against
gram negative organisms . Cetavlon is soluble in water; it has a soapy feel. It may
be used in 1-2 per cent strength.
(2) Savlon : Savlon is a combination of cetavlon and hibitane. Plastic appliances may
be disinfected by keeping them in normal strength savlon for 20 minutes. Clinical
thermometers may be best disinfected in savlon 1 in 6 in spirit in 3 minutes.
24. 3. Halogens and their compounds
a. Chlorine and chlorine compounds : They are potent bactericidal, fungicidal,
sporicidal, tuberculocidal and virucidal.
(1) Bleaching powder : Bleaching powder or chlorinated lime (CaOCl2) is a
white amorphous powder with a pungent smell of chlorine. A good sample of
bleaching powder contains about 33 per cent of "available chlorine". Bleaching
powder is widely used in public health practice in India for disinfection of water,
faeces and urine; and as a deodorant. The chief drawback of bleaching powder is that
it is an unstable compound and loses its chlorine content on storage. Its action is
rapid but brief. A 5 per cent solution (3 to 4 rounded tablespoons to 1 litre of water)
is suitable for disinfection of faeces and urine allowing a period of one hour for
disinfection.
2) Hypochlorites:- household bleach
3) Chlorine tablets
25. b. Iodine :
(1)Iodine solutions or tinctures have been used as antiseptic on skin (e.g.to prepare
incision site prior to surgery) or tissue since long time. Iodine is cheap, readily
available and quick in action.
(2)Iodophores: An iodophore is a combination of iodine and a solubilizing agent or
carrier. The best known and most widely used iodophore is povidone-iodine
(Betadine). They are non irritant and do not stain the skin. Besides their use as an
antiseptic, iodophores have been used for disinfecting blood culture bottles and
medical equipment.
26. 4. 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 washing.
5.Aldehyde:-
a) formaldehyde;- bactericidal , sporicidaland virucidal
• used as aqueous and gaseous form
• A 10% aqueous solution of formalin is frequently used
• Uses
1. To sterilize bacterial vaccines
2. To prepare toxoid from toxins
3. For killing of bacterial cultures and suspensions.
4. For destroying anthrax spores in hair and wool
5. Preservation of tissue for histological examination.
27. b)Glutaraldehyde
• It is a sterilant and a high level disinfectant.
• It is mycobactericidal ,fungicidal, virucidal (including HIV, hep b virus and
enteroviruses)
• It is less toxic and irritant to eyes and skin than formaldehyde.
• It can act in presence of organivc matter and does not damage plastics.
• It is used as 2% buffered solution.(cidex)
• Uses
1. For sterilization of cystoscopies , endoscopes and bronchoscope
2. To sterilize plastic endo tracheal tube s, face masks, corrugates rubber
anaesthetic tubes and metal instruments.
c) Orthophthaldehye
It is a high level disinfectant .
More stable during storage and more rapidly mycobactericidal than glutaraldehdye.
Used for glutaraldehyde resistant mycobacteria.
28. 6. Oxidizing agents
a. Potassium permanganate :
• It is a purplish black crystalline powder
• Strong oxidizing action.
• 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.
b. Hydrogen peroxide:
• High level disinfectant.
• A 3 per cent solution is also used as an antiseptic and for cleaning wounds and
discharging ulcers.
• To disinfect contact lenses, surgical prosthesis and implants.
29. c. Paracetic acid :
• It is a disinfectant produced by reacting hydrogen peroxide with acetic acid.
• It is not deactivated by catalase and peroxidase, the enzymes that break down
hydrogen peroxide.
• It breaks down to environment friendly residue (acetic acid and hydrogen
peroxide).
• Also used in plasma sterilisation procedure.
30. 7. Metals as microbicides
• Heavy metals such as silver have been used for prophylaxis of conjunctivitis of
the new-born, topical therapy for burn wounds, and bonding to indwelling
catheters.
• Inactivation of bacteria on stainless steel surfaces by zeolite ceramic coating
containing silver and zinc ions has also been demonstrated.
• Metals such as silver, iron, and copper could be used for environmental control,
disinfection of water or reusable medical devices, or incorporated into medical
devices.
• Copper salts are used as fungicides.
31. 8) Vapour phase disinfectants
1. Formaldehyde gas :- used for fumigation of operation theatres, wards ,laboratories etcType equation
here. . Formaldehyde gas is generated by adding 150 gm of KMnO4 to 280 ml formalin for 1000 cu.
Feet of room volume . Doors should be sealed and left unopened for 48 hours.steriliastion is achieved by
condensation of gas on exposed surfaces. After completion of disinfection, the effect of irritant vapours
should be nullified by exposure to ammonia vapour.
2. Ethylene oxide :-. Ethylene oxide is explosive, therefore, it is mixed with carbon dioxide (12 per cent).
Water vapour is also often added to the mixture (relative humidity 33 per cent) since it increases the
efficiency of the gas. Ethylene oxide has been effectively used to sterilize cardiac catheters,and
respirators.
32. Materials methods
1. Inoculating wires or loops Red heat
2. Glasswares : syringes, petridishes, test tubes, flasks, universal container, oily fluids
(paraffin)
Hot-air oven
3. Disposable syringes and other disposable items Gamma radiation
4. Culture media Autoclaving
5. Culture media containing serum, egg Tyndallisation
6. Toxin , serum, sugar and antibiotic solutions filteration
7. Milk Pasteurisation
8. Cystoscope and endoscope Glutaraldehyde
9. Sterilisation of operation theatres Formaldehyde gas
10. Infrecative material like soiled dressings , beddings and animal carcasses
11. Skin Tincture iodine, 70% ethanol,
savlon
12. Aprons, gloves, cathetres, surgical instruments except sharp instruments Autoclaving
13 Sharp instruments 5% cresol
14 Rubber, plastic and polythene tubes glutaraldehyde
33. Factors affecting the efficacy of sterilization
1. Cleaning - Failure to adequately clean instruments results in higher bioburden, protein
load, and salt concentration. These will decrease sterilization efficacy.
2. Pathogen type - Spore-forming organisms are most resistant to sterilization. However. the
contaminating microflora on surgical instruments consists mainly of vegetative bacteria.
3. Biofilm accumulation - Biofilm accumulation reduces efficacy of sterilization by impairing
exposure of the sterilant to the microbial cell
4. Luman length and luman diameter - Increasing lumen length and decreasing lumen
diameter impairs sterilant penetration. May require forced flow through lumen to achieve
sterilization.
5. Restricted flow ,Device design and construction. -Sterilant must come into contact with
microorganisms. Device designs that prevent or inhibit this contact (e.g. sharp bends, blind
lumens} will decrease sterilization efficacy. Materials used in construction may affect
compatibility with different sterilization processes.
34. REFERENCE:-
1. Parks, Textbook of preventive and social medicine, 25th edition.
2. Baveja C. P. Textbook of Microbiology, 6th edition.
