This document discusses the history and methods of sterilization and disinfection. It notes that sterilization was developed partly for food preservation and to prevent infection by bacteria. Key developments included Nicolas Appert using heat in 1809, Louis Pasteur inventing pasteurization in 1865, and Charles Chamberland inventing the pressure steam sterilizer (autoclave) in 1879. The document defines sterilization, disinfection, and other related terms. It describes various physical methods like heat and chemical methods like alcohols, aldehydes, and gases that can be used to kill microorganisms. Different classes of medical devices and the most resistant and least resistant types of microbes are also discussed.

1. STERILISATION AND
DISINFECTION
Presented by :
Maj Sulochana Kumari
P B Diploma in Operation Room
Nursing

2.  Sterilization grew partly out of preservation and
also by trying to prevent infection caused by
bacteria.
 Nicolas Appert-1809 heat as a preservative
method.
 Louis Pasteur -1865 invented pasteurization.
 Charles Chamberland –1879 invented
pressure steam sterilizer (autoclave).
 Joseph lister-1880 invented carbolic acid
spray.
HISTORY

3. WHY NEEDED?
Microorganisms are
ubiquitous.
Since they cause
contamination, infection
and decay, it becomes
necessary to remove or
destroy them from
materials or from areas.

4. DEFINITIONS
 Sterilization – process by which an article,
surface or medium is freed of all living
microorganisms either in the vegetative or
spore state.
 Disinfection – process of destroyingall
pathogenic microorganisms capable of
producing infections but not necessarily
spores.

5.  Asepsis – It refers to the complete absence of
viable pathogenic microorganisms in any
environment.
 Antiseptics – Chemical disinfectants which
can be safely applied to skin or mucous
membrane and are used to prevent infection
by inhibiting growth of bacteria.
 Bactericidal – Agent which can kill bacteria.
 Bacteriostatic – Agent which only prevents
multiplication of bacteria.
DEFINITIONS

6. HOW CAN MICROORGANISMS
BE KILLED ??
 Denaturation of proteins
 Oxidation
 Filtration
 Interruption of DNA synthesis/repair
 Interference with protein synthesis
 Disruption of cell membranes

7.  Most Resistant
 Endospores
 Mycobacteria
 Fungal spores
 Small non-enveloped viruses (polio,
rota virus, rabies)
 Vegetative fungal cells
 Enveloped viruses (Herpes,
 Hepatitis B and C, HIV)
 Least Resistant

8.  Proposed by Earl H. Spaulding
 Categorized into 3 categories
 Critical devices
 Semi critical devices
 Non critical devices
CLASSIFICATION OF MEDICAL
DEVICES FOR REPROCESSING

9. PHYSICAL
METHODS
CHEMICAL
METHODS
S
T
E
R
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L
I
S
A
T
I
O
N
Sunlight
Drying
Heat
Dry heat
Moist heat
Filtration
Radiation
Alcohols
Aldehydes
Dyes
Halogens
Phenols
Surface-active agents
Metallic salts
Gases

10. PHYSICAL METHODS OF
STERILISATION

11. SUNLIGHT
❖ Possesses bactericidal activity.
HEAT
❖ Most reliable method.
❖ Can be used either in dry form or moist form.

13. ❖ Principle - Killing effect is due to
 Protein denaturation
 Oxidative damage

14. FLAMING
❖ Bunsen flame is used.
❖ Uses – Scalpel blades, inoculation wires
and loops, glass slides, cover slips.

15. INCINERATION
❖ Excellent method.
❖ Materials are reduced to ashes by burning.
❖ For contaminated and pathological materials
at a high temperature.

16. INCINERATOR
FUEL GAS OUT
COMBUSTION
AIR INLET
BURNER OIL
FUEL GAS
OUT
ASH DOOR

17. HOT AIR OVEN
 Kills by oxidation effects
 Utilizes dry heat to sterilize
 Used to sterilise culture
media, petri dish, specimen
bottle,culture bottle and test
tubes,liquid paraffin

18. TIME-TEMPERATURE
COMBINATIONS
TEMPERATURE HOLDING TIME
160 oC 120 minutes
170 oC 60 minutes
180 oC 30 minutes

19. STERILISATION CONTROL
 Spores of Bacillus subtilis subsp.niger (NCTC
10075 or ATCC 9372)
 Thermocouples
 Browne’s tube with green spot

20. MOIST HEAT STERILISATION

21. TEMPERATURE BELOW 100o C
(PASTEURISATION)
.
❖ HOLDER METHOD – Heating
at 63o C for 30 minutes.
❖ FLASH PROCESS – Heating at
72o C for 15-20 seconds.

22.  Inspissation
 Vaccine Bath
TEMPERATURE BELOW 100o C

23.  Vegetative bacteria are killed at 90-100 o C.
 Requires immersion in water and boiling for
10-30 minutes.
TEMPERATURE AT 100o C
(BOILING)

24. TYNDALLISATION
❖ Steam at 100o C for 20 mins for 3 consecutive
days
PRINCIPLE - The first exposure kills all vegetative
forms and bacteria and spores which survived
the heating process will germinate into
vegetative state and are killed in subsequent
exposure.

25. TEMPERATURE ABOVE 100O C
(AUTOCLAVE)
❖ Most reliable method of sterilisation.
❖ Works on the principle of Steam under
pressure.
❖ Invented by Charles
Chamberland in 1879.

26. TYPES OF AUTOCLAVES
 Gravity displacement sterilisers
 High vaccum sterilisers
 Autoclaves used in health care setting
 laboratory autoclave
 Hospital dressing sterilisers
 Instrument sterilisers

27. HORIZONTAL AUTOCLAVE

28. VERTICAL AUTOCLAVE

29. DOWNWARD DISPLACEMENT
LAB AUTOCLAVE

30. STERILISATION CONTROL
❖ Bacterial spores – Bacillus stearothermophilus
❖ Thermocouple
❖ Brown’s test
❖ Autoclave tape

31. CLASS I INDICATER TAPE

32. FILTRATION

34. CANDLE FILTERS
 Hollow ‘Candle’ form
 Used for purification of water

35. ❖ Types-
 Unglazed Porcelain filters eg-
Chamberland and Doulton filter
 Diatomaceous earth filters eg- Berkfeld
and Mandler filter

36. ASBESTOS FILTERS
❖ Disposable, single use discs with
high adsorbing capacity
❖ Discarded – Cariogenic potential

37. MEMBRANE FILTERS
 Made up of variety of polymeric materials such
as cellulose nitrate, cellulose diacetate,
polycarbonate and polyester.

38. AIR FILTERS
 Mainly HEPA (High Efficiency Particulate air)
filter is used

39. RADIATION

40. IONISING RADIATION
 Lethal action – breakdown of single stranded or
sometimes double-stranded DNA and effect on
other vital cell component
 X-rays, gamma rays and beta
rays

41. NON-IONISING RADIATION
❖ Electromagnetic rays with wavelengths
longer than those of visible light are used.
❖ Ultraviolet and infrared rays

42.  Alcohols – Ethyl, Isopropyl,
Trichlorobutanol
 Aldehydes – Formaldehyde,
Glutaraldehyde
 Dyes
 Halogens
 Phenols
 Surface Active Agents
 Metallic Salts
 Gases – Ethylene Oxide,
Formaldehyde, Betapropiolactone.
CHEMICAL AGENTS

43. LEVEL OF DISINFECTANTS
 High-level disinfectants
 Intermediate-level disinfectants
 Low-level disinfectants

44. MODES OF ACTION OF
CHEMICAL DISINFECTANTS
 Protein coagulation
 Disruption of cell membrane
 Removal of free sulfhydryl groups

45. ALCOHOLS
 Ethanol (80% v/v ethyl alcohol) or 2-propanol
(60-70% v/v iso- propyl alcohol) solutions are
used to disinfect skin and decontaminate clean
surfaces.

46. ALDEHYDES
 Formaldehyde
 Glutaraldehyde
 Ortho-phthaladehyde

47. FORMALDEHYDE
 Formalin is 37% w/v formaldehyde gas in water
 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

48.  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.
GLUTARALDEHYDE

49. Use: for instruments such as
cystoscopes, bronchoscopes,
corrugated rubber anesthetic
tubes, face masks, endotracheal
tubes, metal instruments,
polythene tubing.

50.  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.
HYPOCHLORITE

51. PHENOLS
 Effective against bacteria (especially gram +ve
bacteria) and enveloped viruses.
 Used for decontamination of the hospital
environment, including laboratory surfaces.
 Ex Cresol, Chlorhexidine,
Chlorxylenol, Hexachlorophines

52. HALOGENS
Commonly used
disinfectants
Bactericidal, Sporicidal,
Virucidal
2% Iodine in 50%
alcohol(tincture) which
kills more rapidly and
effectively than alcohol

53. IODINE COMPOUNDS
 Iodine is used in aqueous or alcoholic
solution.
 Rapidly effective against most
microorganisms.

54. OXIDISING AGENTS
 Hydrogen peroxide
 Paracetic acid
 Plasma sterilisation

55. QUATERNARY AMMONIUM
COMPOUNDS
 Quaternary ammonium compounds are positively
charged (cationic) surface-active disinfectants.
 Effective against Gram-positive bacteria and
lipid- containing viruses.
 Eg. Benzalkonium chloride, alkyldimethylbenzyl
ammonium chloride, and cetylpyridinium chloride.
 Used for cleaning of floors of hospitals.

56. SURFACE ACTIVE AGENTS
 Acetyl trimethyl ammonium bromide
 Benzalkonium chloride

57. METALLIC SALTS
 Silver
 Copper
 Mercury salts

58. DYES
Aniline dyes
Acridine dyes

59. VAPOUR PHASE DISINFECTANTS
 Formaldehyde gas
 Ethylene oxide gas
 Betapropiolactone

60. GASES
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.

61. ETO MACHINE
.

62. BETAPROPIOLACTONE
(BPL)
 It is a condensation product of ketone and
formaldehyde having a boiling point of 163’C.
 It is capable of killing all microorganisms including
viruses.

63.  Sterilization and Disinfection are costly and
time consuming process.
 However it is essential in all health care
facilities to avoid spread of disease.
 It depends on the ethics of the instrument
users.
 Users should keep in mind that contaminated
instrument present risk to patient as well as
the user himself.
CONCLUSION

64. VARIOUS DISINFECTANTS
USED IN OT

65. VARIOUS DISINFECTANTS
USED IN OT

66. THANK YOU