The document discusses various methods of disinfection and sterilization used in laboratories. It defines disinfection as reducing microorganisms through physical and chemical means, while sterilization completely removes all microbial life including spores. Common chemical disinfectants discussed are alcohols, hypochlorites, phenol, and their effectiveness against different microbes. Heat and chemical sterilization methods like steam autoclaving, dry heat, ethylene oxide gas, and glutaraldehyde liquid are described. Radiation sterilization using gamma rays is also covered. The document emphasizes that while sterilization is important, hand washing remains a key practice to prevent infection.
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Disinfection
1. Disinfection & Sterilization
Dr : Dina Ramadan
Microbiologist In Central Health Laboratory
Ministry of Health
Quality Manager
Training Workshop on “Laboratory Risk Management”
2-4 Oct, 2012, • Cairo, Egypt
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.
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
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
• protein denaturation 1. Protein denaturation &
1. Oxidative damage coagulation
2. Toxic effects of 2. Latent heat liberated
increased levels of when steam condenses on
electrolytes cooler surface
3. 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. 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)
19. 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, )
20. 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.
21. 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
22. 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
23. 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.
24. Sterilizing Filter
• Aqueous liquids sterilized by forced passage through filter of
porosity small enough to retain any microorganism.
1) Membrane filters:
• Manufactured from variety of polymeric material such as
cellulose diacetate, polycarbonate and polyester, as
disc.
• Membrane made in 2 ways
I. Labyrinthine pore membranes: Bacteria & yeast
II. Capillary pore membranes: For viruses
Filters may be supplied with plastic holders pre sterilized for single
use, or mounted in re-usable holders and fitted to filtration
vessels.
25. Sterilizing Filter
2)Syringe filters:
• Membrane 13-25mm diameter.
• Fitted in syringe like holders of stainless steel or
polycarbonate.
• Used for sterilization of small volumes of fluid.
3)Vacuum and in- line filters:
• Membranes of 25-45 mm diameter are used either
with in line filter holders of Teflon or stainless
steel and aluminum.
• Used for sterilization of large volumes of air and
liquid.
27. 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.