1. Sterilization and Disinfection
M.N Priyadarshanie B.Sc.Nursing(Hons)

2. I. Sterilization It is one of the basic steps in surface asepsis.
Definition: Sterilization refers to the use of different procedures to destroy all forms of microorganisms including bacterial spores.

3. What to sterilize? It is mandatory to sterilize :
all instruments that penetrate soft tissues and bone.
Instruments that are not intended to penetrate the tissues, but that may come into contact with oral tissues.
If the sterilization procedure may damage the instruments, then, sterilization can be replaced by Disinfection procedure

4. II. Disinfection It a is less lethal process than sterilization.
Definition: It is a procedure intended to reduce microorganisms as far as possible (but not bacterial spores).
Thus, disinfection can never replace sterilization

5. Which procedure to use? Procedure Category Sterilization
Items in each category
Category
Sterilization
Items that: (1) enter the tissue; (2) Enter vascular system; (3) through which blood flows
Critical
High level disinfection
Items that: (1) touch mucous membranes; (2) touch non-intact skin (e.g. endoscopes, respiratory therapy equipment, and diaphragms)
Semi-critical
Low level disinfection
Items such as bedpans, blood pressure cuffs, and bedside tables
Non-critical

6. I. Sterilization - Process

7. Sterilization – Instrument Packing
Often instruments are packed for sterilization
Packing depend on the intended shelf life after sterilization.
The available packing options are:
Textile has shelf life of 1 month
Paper has shelf life of 1-6 months
Nylon, glass, and metal have shelf life of 1 year if tightly closed

8. Sterilization Principles
There are 3 different sterilization principles:
Heat sterilization
Chemical sterilization
Radiation sterilization
Each principles is discussed in the following sections.

9. 1. HEAT STERILIZATION

10. 1. Heat Sterilization Advantages:
It is the simplest, most effective and inexpensive method.
There are 2 procedures depending on the tolerance of the material used:
Steam sterilization (Autoclaving)
Dry heat sterilization

11. 1.a. Heat – Steam Sterilization
Use saturated steam above 100º C on packed items.
Objects occupy 4/5 of autoclave volume to facilitate circulation.
Process is divided into 3 periods as follows:
Pre-vacuum period:
air is withdrawn from device
Sterilizing period: steam is introduced under pressure t specific temperatures & times.
Post-vacuum: steam is withdrawn to dry autoclave

13. Steam Sterilization Advantages & Disadvantages
good penetration
maintains integrity of liquids (e.g. Lubricants) due to the 100% humidity within the chamber.
Disadvantages:
Non stainless steel metal items corrode
may damage plastic and rubber items
sharp instruments get dulled.

14. 1.b. Dry-Heat Sterilization
Involves heating at atmospheric pressure and often use a fan to obtain uniform temperature by circulation.
Heat at
180º for half hour ,
170º for 1 hr.,
or 160º C for 2 hrs.
Times are the periods during which object is maintained at the respective temperature

15. Dry-Heat Sterilization Disadvantages
Less reliable than autoclaving
sharp instruments get dulled
Many materials do not tolerate dry heat

16. 2. CHEMICAL STERILIZATION

17. 2. Chemical Sterilization - Types
The chemical compounds used can be:
Gas Sterilization
Liquid Sterilization
Generally, chemical sterilization procedures have the disadvantages of presenting health hazards to users
(e.g. poisonous, flammable )

18. The gas used in this procedure is ethylene oxide.
Keep objects in constant atmospheric humidity.
Heat to temperatures between 30º and 60º C.
maintain for a period of 10 hrs.
Residual ethylene oxide must be ventilated
Formalin gas autoclaves have been developed for sterilizing endoscopes and anaesthetic apparatus.
2.a) Gas Sterilization

19. Gas Sterilization – Disadvantages
Ethylene oxide (& formalin) autoclaves have the following disadvantages:
Difficult to operate
Unsuitable for hospitals but used in industry (e.g. for sterilizing disposable materials that can not tolerate high temperatures).

20. 2.b) Liquid Sterilization
Can be performed with buffered glutaric aldehyde.
Procedure:
Immerse object in liquid for several hours.
Rinse with sterile water after end of procedure.

21. 3. RADIATION STERILIZATION

22. 3. Radiation Sterilization
Provides effective way of sterilization when used in high doses.
Gamma radiation
Procedure:
Expose objects for about 24 hrs.

23. Radiation Sterilization Advantages and Disadvantages
Clean process
Dry process
Ensures full exposure of object from all directions
Disadvantages:
Posses threat to humans (radiation)
Lengthy process
Requires very qualified personnel

24. II. DISINFECTION

25. Disinfection - Types
Disinfection can not kill all microorganisms but only reduce its number.
Disinfection can be accomplished with:
Heat disinfection
Chemical disinfection
Object that can be disinfected are bedpans, patient skin before operation and surgeon hands before putting gloves.

26. 1. Heat Disinfection
It is accomplished by boiling water at atmospheric pressure for at least 20 min’s

27. 2. Chemical disinfection
Number of different agents are used according to tolerance of objects and infectious agents.
Using phenol with cleaning component destroy the membrane of microorganisms.
Using 70% alcohol for skin which denatures proteins of microorganisms.
Use soap containing hexachlorophene for hands.
In case of hepatitis use 5% solution of chloramines or heat disinfection

28. Asepsis – Summary

29. Disinfection and Sterilization - New methods

30. Chemical Antimicrobials
Agent
Mechanisms of Action
Comments
Surfactants
Membrane Disruption; increased penetration
Soaps; detergents
Quats (cationic detergent)
Denature proteins; Disrupts lipids
Antiseptic - benzalconium chloride, Cepacol; Disinfectant
Organic acids and bases
High/low pH
Mold and Fungi inhibitors; e.g., benzoate of soda
Heavy Metals
Denature protein
Antiseptic & Disinfectant; Silver Nitrate
Halogens
Oxidizing agent Disrupts cell membrane
Antiseptic - Iodine (Betadine) Disinfectant - Chlorine (Chlorox)
Alcohols
Denatures proteins; Disrupts lipids
Antiseptic & Disinfectant Ethanol and isopropyl
Phenolics
Disrupts cell membrane
Disinfectant Irritating odor
Aldehydes
Denature proteins 
Gluteraldehyde - disinfectant (Cidex); Formaldehyde - disinfectant
Oxidizing agents
Denature proteins
Hydrogen peroxide – antiseptic; Hydrogen peroxide – disinfectan; Benzoyl peroxide – antiseptic
Chemical Antimicrobials

31. Soaps are sodium or potassium salts of fatty acids, a natural product
Detergents, instead, are artificial surfactants
While soaps are always negatively charged, some detergents are negatively charged while others are positively charged
One example of a positively charged detergent are quaternary ammonium compounds (a.k.a., quats)
Soap & Detergents

32. Halogens are the seventh (VII) column of the periodic table of elements
Two halogens are regularly employed as antimicrobials: Iodine and Chloride
Iodine: commonly used as an antiseptic against all microbes, fungi, and viruses
Iodine: It inhibits protein synthesis and oxidizes –SH groups of amino acids
Chlorine: Used as a disinfectant (10% bleach)
Chlorine: Hypochlorous acid (HOCl) is a product, formed in water, that is the active form of the disinfectant
Chlorine: Applied in treatment of drinking water, swimming pool, and sewage
Halogens

33. and even in the presence of organics,
Glutaraldehyde is capable of effectiving sterilization—at room temperature, even against endospores,
and even in the presence of organics,
but achieving sterilization requries many hours of exposure… and it is nasty stuff to work with!
Glutaraldehyde

34. Conclusion In summary:
Sterilization and disinfection are costly and time consuming process
However, it is an essential in all health care facilities to avoid spread of diseases.
It depends on the ehtics of the instrument users.
Users should keep in mind that contaminated instrument present risk to patient as well as the user himself.

35. Thank you.