Microorganisms are the agents of contamination, infection and decay. Hence it becomes necessary to remove them.

1. STERILISATION AND
DISINFECTION
SREEVIDYA V S
NURSING TUTOR/ CLINICAL
INSTRUCTOR
CENER, AIIMS RISHIKESH

2. INTRODUCTION
HOW CAN YOU SAY SOMETHING IS DIRTY OR NOT CLEAN?
HOW WILL YOU CLEAN DIRTY OBJECTS?

3. INTRODUCTION
Microorganisms are the agents of contamination, infection and decay.
Hence it becomes necessary to remove them.

4. Terminologies
• Unclean/dirty: not clean or visibly soiled
• Contaminated/Infected :affected by an organism that can cause
disease

5. Terminologies
• Cleaning : the act of removing visible dirt/ soil from the surface of
floor, utensils, glass, metals etc.
• Decontamination : it removes or destroys contamination so that
infectious agents cannot reach a susceptible site in sufficient
quantities to initiate infection, or other harmful response
• Physical cleaning
• Water purification
• Ultrasonic cleaning
• Antisepsis
• Disinfection
• Sterilization

7. Terminologies
• Antiseptic: antiseptic prevent the growth and development of
microorganisms in the body surface.
• Antibiotic : chemical substances usually kill and prevent the growth of
microorganisms

8. Terminologies
• Disinfection :The process of killing (inactivating) harmful and
objectionable bacteria, cysts and other microorganisms (pathogenic)
by various agents.
• Sterilization : It is the removal of all forms of microorganisms from the
surface of an object. It includes both spore and vegetative forms.

10. WHO AM I?

11. HIGH RISK ITEMS

12. CLEANING

14. DISINFECTION

15. CONCURRENT DISINFECTION
• Concurrent disinfection is the immediate disinfection of all
contaminated articles and bodily discharges during the course of the
disease
• Concurrent disinfection of the contaminated articles immediately,
then and there during the course of illness. It includes cleaning the
isolation unit daily with effective disinfectant.

16. TERMINAL DISINFECTION
• Terminal disinfection means disinfection of the patients unit and all
the articles used after the discharge, transfer or death of the patient
who was suffering from the contagious disease
• It means after the patient has recovered from a communicable
disease, the disinfection of the room and articles used by him is done
after his discharge from the unit or transfer or death

17. PRE-CURRENT/ PROPHYLACTIC DISINFECTION
• Before any disease condition
• As a prophylactic measure.

18. DISINFECTANT- TYPES
• Alcohols
• Aldehydes
• Halogens
• Oxidising agents
• Quaternary ammonium compounds

19. Alcohols
• Alcohols, usually ethanol or isopropanol, are wiped over benches and
skin and allowed to evaporate for quick disinfection.
• They have wide microbiocidal activity, are non corrosive, but can be a
fire hazard.
• They also have limited residual activity due to evaporation, and have
a limited activity in the presence of organic material.
• Alcohols are more effective combined with water—70% alcohol is
more effective than 95% alcohol. Alcohol is not effective against
fungal or bacterial spores.

20. Aldehydes
• Aldehydes, such as Glutaraldehyde (2%), have a wide microbiocidal
activity and are sporocidal and fungicidal. They are partly inactivated
by organic matter and have slight residual activity.
• CONTACT TIME – 20MIN IN 20 DEGREE CELSIUS

21. Halogens
• Chlorine is used to disinfect swimming pools, and is added in small
quantities to drinking water to reduce waterborne diseases.
• Hypochlorites (Sodium hypochlorite), often in the form of common
household bleach, are used in the home to disinfect drains, and
toilets.
• Iodine has been used as an antiseptic for skin cuts and scrapes.

22. HYPOCHLORITE
• 1% SODIUM HYPOCHLORITE
• AVAILABLE FORM = 5%
• Used for spillage management - HIV , HEP B

23. Oxidising agents
• Hydrogen peroxide is used in hospitals to disinfect surfaces.
• A 3% solution is also used as an antiseptic.
• When hydrogen peroxide comes into contact with the catalase
enzyme in cells it is broken down into water and a hydroxyl free
radical. It is the damage caused by the oxygen free radical that kills
bacteria.
• However, recent studies have shown hydrogen peroxide to be toxic to
growing cells as well as bacteria; its use as an antiseptic is no longer
recommended.

24. Phenol
• Phenolics are the active ingredient in most bottles of "household
disinfectant".
• They are also found in some mouthwashes and in disinfectant soap
and handwashes.
• Phenol is probably the oldest known disinfectant as it was first used
by Lister, when it was called carbolic acid.
• It is rather corrosive to the skin and sometimes toxic to sensitive
people, so the somewhat less corrosive phenolic o-phenylphenol is
often used in favour.

25. Quaternary ammonium compounds
• Quaternary ammonium compounds (Quats), such as benzalkoniuM
chloride, are a large group of related compounds.
• Some have been used as low level disinfectants.

26. Air disinfection/fumigation
• Fumigation is the process of using chemical smoke to kill pests like
insects or rodents.
• Also be used as disinfection technique in hospital.
• The unit must be closed before fumigation.

27. Factors influencing activity of disinfectants
• Activity directly proportional to temperature.
• Directly proportional to concentration up to a point – optimum
concentration.
• After this level no advantage in further increases in concentration.

28. Factors influencing activity of disinfectants
• Disinfectants may be inactivated by :
• Dirt
• Organic matter : Proteins, Pus, Blood, Mucus and Feces.
• Non organic: Cork, Hard water and Some plastics.
• Time : Disinfectants need time to work.
• Range of Action : Disinfectants not equally effective against the whole spectrum
of microbes. e.g. Chlorhexidine less active against Gram negative bacteria than
Gram positive cocci.
Hypochlorites and Gluteraldehyde are more active against hepatitis viruses than
most other disinfectants.

29. Hospital disinfection methods
Article Disinfectant
• Floors, walls Phenolics fluids 1-2%
• Surfaces tables Hypochlorite, Alcohol
Skin
• Surgeons’ hands Chlorhexidine, Iodin, alcohol
• Patient skin 70% Alcohol, Iodine
Endoscopes Gluteraldehyde 2% (Cidex), steam
Thermometers 70% Alcohol

30. STERILIZATION

31. STERILIZATION
• The Central Sterile Services Department (CSSD)
• Also called Sterile Processing Department (SPD) or
• Central Supply Department (CSD)

32. Methods of Sterilization
1. Physical methods:
• Heat ( dry heat & moist heat)
• U.V. Light
• Ionizing Radiation
• Filtration
2. Chemical method:(used for heat sensitive equipments)
• Ethylene Oxide
• Gluteraldehyde .

33. PHYSICAL METHODS
HEAT : Most important should be used whenever possible
Types:
1. Dry heat at temperature of 160˚C for one hour
2. Moist heat eg. Autoclave at 121 or 134 C for 10 or 15
minute

34. Sterilization by Heat - Common methods
Dry Heat
• Dry Heat- kills microorganisms by destroying their oxidative processes.
• Simplest method is exposing item to be sterilized to the naked flame e.g. Bunsen burner-
for sterilizing bacteriological loops, knives, blades.
• Hot air oven expose items to 160 °C for 1 hour.
• Has electric element in chamber as source of heat plus a fan to circulate air for
even distribution of heat in chamber. Oven without fan is dangerous. Used for
items that are lacking water such as:
-Metals
-Glassware
-Ointment / Oils/ Waxes /Powder

35. Moist Heat
• Uses hot water. Moist heat kills microorganisms by denaturating proteins.
• Autoclaving – standard sterilization method in hospitals.
• The equipment is called Autoclave and it works under the same principle as
the pressure cooker where water boils at increased atmosphere pressure i.e.
because of increase pressure the boiling point of water is >100 °C.
• The autoclave is a tough double walled chamber in which air is replaced by
pure saturated steam under pressure.

37. • The air in the chamber is evacuated and filled with saturated steam. The chamber
is closed tightly the steam keeps on filling into it and the pressure gradually
increases. The items to be sterilized get completely surrounded by saturated
steam (moist heat) which on contact with the surface of material to be sterilized
condenses to release its latent heat of condensation which adds to already raised
temperature of steam so that eventually all the microorganisms in what ever
form are killed.
• The usual temperature achieved is 121 °C , exposure time of only 15 mins .

38. Advantages of Autoclave
• Temp. > 100 C therefore spores killed.
• Condensation of steam generates extra heat.
• The condensation also allows the steam to penetrate rapidly into
porous materials.
• Note: for all invasive procedures at operating room or clinics,
autoclavable equipments should be used.

39. Monitoring of Autoclaves
• 1. Physical method: use of thermocouple to measure accurately the temperature.
• 2. Chemical method: it consists of heat sensitive chemical that changes color at
the right temperature and exposure time.
• e.g. a)- Autoclave tape
• b)- Browne’s tube.
• 3. Biological method: where a spore-bearing organism is added during the
sterilization process and then cultured later to ensure that it has been killed.
• pores from B. stearothermophilus, a microorganism that is
inactivated when exposed to 121.1oC

41. Moist heat: Other Applications
Pasteurization
• Used heat at temperatures sufficient to inactivate harmful organism in milk. The
temperatures of sterilization is not achieved .
• Temperature may be 74°C, for 3-5 seconds. ( Flash methods or
62°C for 30 minutes. ( Conventional method ).
Boiling – quite common especially in domestic circumstances.

42. Other physical methods : Radiation
• U.V. light
• Has limited sterilizing power because of poor penetration into most materials.
Generally used in irradiation of air in certain areas such as operating rooms
and tuberculosis labs.
• Ionizing radiation-
• e.g. Gamma radiation: has greater energy than U.V. light, therefore more
effective. Used mainly in industrial facilities e.g. sterilization of disposable
plastic syringes, gloves, specimens containers and Petri dishes.

43. Sterilization by Chemical Methods
Useful for heat sensitive materials e.g. plastics and lensed endoscopes).
1. Ethylene Oxide Chamber
Ethylene oxide alkylates DNA molecules and thereby
inactivates microorganisms.
Ethylenes oxide may cause explosion if used pure so it is
mixed with an inert gas .Requires high humidity (50-60% ) .Temperature : 55-60°C and exposure period
4-6 hours.
2. Activated alkaline Gluteraldehyde 2%
Immerse item in solution for about 20 mins. If Mycobacterium tuberculosis or spores present then
immersion period 2-3 hours.

44. Other physical methods : Filtration
• May be done under either negative or positive pressure. Example ;
membrane filter made of cellulose acetate. Generally removes most
bacteria but viruses and some small bacteria e.g. Chlamydia &
Mycoplasma may pass through. Thus filtration does not technically
sterilize items but is adequate for circumstances under which is used.
• Main use: for heat labile substances e.g. sera, antibiotics.

45. Chemical Methods
• Some strong chemical substances may be used to achieve
sterilization ( kill spores)
e.g. Gluteraldehyde and Ethylene oxide. Used for heat sensitive
equipments.
CONTACT TIME 10HRS

46. High-touch areas
• High-touch areas are surfaces that are frequently touched by
healthcare providers and clients.
• Examples of high-touch areas include:
• Door handles
• Light switches
• Alcohol-based solution dispensers
• Sink taps
• Call bells
• Bed rails

47. Important points
• Any instrument or item used for sterile body site should be sterile.
• Any instrument or item used for non-sterile body site can be
disinfected.
• Hand washing is the most important to prevent hospital acquired
infection.