types of disinfection and sterilization in the microbiological lab

1. Disinfection &Sterilization
Dr : Dina Ramadan
Microbiologist In Central Health Laboratory
Ministry of Health
Cairo-Egypt
Quality Manager

2. Definitions
Disinfection:
It is a procedure intended to reduce microorganisms as far as
possible (but not bacterial spores) by physical and chemical
means
Sterilization:
the complete removal or destruction of all forms of microbial
life including bacterial spores
Remember :
No absolute assurance that there is 0 microorganism

3. Other Definitions
Disinfection
The use of a physical or chemical procedure to eliminate
pathogenic microorganisms on inanimate objects
Sterilization
The use of a physical or chemical procedure to destroy
all microbial life, including large numbers of highly
resistant bacterial spores.

4. Chemical Disinfectant

5. Alcohols
 There are two water-soluble alcohol can be used
in lab: ethyl alcohol and isopropyl alcohol.
 Concentration required : 60-90% in water
 Mode of its action : it denaturing bacterial proteins
 its Flammable, Can be removed from disinfected
articles by flaming.

6. Alcohols effect on bacteria
 they are bactericidal against for the vegetative
forms of bacteria (Gram + and Gram -);
 also they are tuberculocidal, fungicidal, and
virucidal against enveloped viruses (HIV,
influenza ,herpes viruses).
 not effective against bacterial spores and have
limited effectiveness against nonenveloped viruses
( adenovirus, rotavirus)

7. Alcohols
 Higher concentrations are
less effective as the action
of denaturing proteins is
inhibited without the
presence of water

8. Hypochlorite's
 it has broad spectrum antimicrobial
effect
 inexpensive and fast acting,
 It is recommended for disinfection of
counter tops and work surfaces,

9. Chlorine
 It is very effective against vegetative bacteria and
viruses like HBV and HIV viruses, therefore its
use is recommended at 1:10 dilution for
disinfection of blood spills
 not much useful against spores

10. Phenol
• It effective against bacteria
(especially gram +ve bacteria)
and enveloped viruses.
• They are not effective against non
enveloped viruses and spores.
• This compounds is used for decontamination of the
hospital environment, including laboratory surfaces.

11. No Disinfectant is substitute for the
following Procedures
 Hand washing (hand hygiene);
 use of personal protective equipment
(PPE )in the lab
 Environmental cleaning
 Appropriate handling of waste and
 Taking care of yourself (e.g. immunization)

12. Yet no substitute for washing hands
Do not forget to Wash Your Hands
 Immediately on arrival at work
 After handling specimens
 After removing gloves
 After using the toilet
 Before leaving work

13. Sterilization
1. Heat sterilization
2. Chemical sterilization
3. Radiation sterilization

14. Heat Sterilization
It is the simplest, most effective and inexpensive
method.
Types of heat sterilization :
a) Steam sterilization (Autoclaving)
b) Dry heat sterilization

15. Mechanism of Action
 DRY HEAT:  MOIST HEAT:
2. protein denaturation 2. Protein denaturation &
3. Oxidative damage coagulation
4. Toxic effects of 3. Latent heat liberated
increased levels of when steam condenses on
electrolytes cooler surface
4. Hydrolysis & breakdown
of bacterial proteins

16. Steam Sterilization (MOIST HEAT )
Advantages:
 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

17. Dry-Heat Sterilization
 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.
Temperature (°C) Time (minutes)
120 480
140 180
150 150
160 120
170 60
180 30

18. Sterility Indicators
Chemical indicators
Temperature for sterilization have been met. Do not address
time or pressure
Biological indicators
Temperature, time and pressure for sterilization have been met
NOTE:
Neither indicator is a guarantee of sterilization if:
Autoclave is overpacked
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19. Dry-Heat Sterilization
 Advantages:
 It is effective and safe for metal instruments because the
process does not dull instrument edges or rust/corrode
the instruments.
 Disadvantages:
 Less reliable than autoclaving
 Many materials do not tolerate
dry heat (as media)

20. Chemical Sterilization
 The chemical compounds used can be:
a) Gas Sterilization
b) Liquid Sterilization
 Generally, chemical sterilization procedures have
the disadvantages of presenting health hazards to
users (e.g. poisonous, flammable, )

21. Gas Sterilization
 The gas used in this procedure is ethylene oxide.
 Keep objects in constant atmospheric humidity.
 Heat to temperatures between 30º and 60º C,for a
period of 10 hrs.
 Residual ethylene oxide must be ventilated
 It is used for sterilizing endoscopes and ansthetic
apparatus.

22. 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.
 It used in hospitals for sterilization of surgical
instruments, rubber or plastic equipment
which cannot be heat sterilized

23. Radiation Sterilization
 Provides effective way of sterilization when
using non ionizing radiation in high doses
(Gamma radiation ).
 it is clean process
 dry process
 the object full exposure from all directions

24. Non ionizing radiations
 UV RAYS (ultra violet)
are used to sterilize internal Surfaces of safety
cabinets, entry ways, Operation theaters etc.
 IR RAYS ( infra red) are used for rapid mass
sterilization of pre packed items such as syringes,
catheters etc.

25. Asepsis
Sterilization Disinfection
Heat Chemical Radiation Heat Chemical
Steam Gas Gamma Boiling water Phenol
Dry heat Ethylene oxide Alcohol 70%
Formalin Hexachlorophene
Heat or
Liquid chloramines solution
Glutaric
Aldehyde

26. In summary
 Sterilization and disinfection are costly and time
consuming process
 However, it is an essential in all health care
facilities to avoid infection.
 It depends the material and users of instrument.
 Staff should keep in mind that contaminated
instrument present risk to the sample as well as
the user himself.

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