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STERILIZATION & DISINFECTION

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Sterilization –

The processes that removing or killing all the microbial life and viruses on an object or any material.

Disinfection-

The processes that result in the destruction of only the vegetative forms of microbial life (pathogenic organisms) but not spores.

Definitions

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VARIOUS METHODS EMPLOYED

CLASSIFICATION
V) STERILIZATION METHODS
CHEMICAL AGENTS
PHYSICAL AGENTS
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PHYSICAL AGENTS
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HEAT

Heat -Is most practical and dependable method of sterilization.

The factors influencing sterilization by heat are:

• 1-Nature of heat- dry heat or moist heat.
2-Temperature & time.
3-Number of microorganisms present.
4-species of m.o.
5-Type of material to be sterilized.
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DRY HEAT

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FLAMING

• A simple & effective method.
• Loops or wires, needle , glass slides, cover slips
• Instruments held on a Bunsen flame till red-hot.



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flaming

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INCINERATION

• In the past, bodies of disease victims were burned to prevent spread of infection.
• This is an excellent method for safely destroying contaminated materials.
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incinerator

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HOT AIR OVEN

This is the most widely used method of
sterilization by dry heat.
• Sterilizing cycle
• Sterilization hold time – It is set to 160o C for 2hours or 170o C for 1hour or 180o C for 30min
Uses-
Glassware, forceps, scissors,scalpels,pharmaceuticals etc.
Disadvantages:
Long sterilization cycle.
Requires an accurate pyrometer.
May damage heat sensitive plastic.
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MOIST HEAT

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1.Pasteurization –

The material is heated at


slow method - 630C for 30 minutes

Fast method - 720C for 15 sec followed by sudden cooling 130C or lower.

For example pasteurization of milk, This will kill ALL non-spore forming pathogens such as Mycobacterium tuberculosis, Brucella abortus and various Salmonellae, so that this method can be used to kill food pathogen.

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boiling

Boiling at 100o C for 5-10 min is sufficient to kill ALL vegetative organisms & many but NOT all spore-forming microorganisms, used to sterile water.
Sporing bacteria require prolonged periods of boiling
Hard water should not be used
Adding 2% NaHCo3 increases efficacy
Not recommended for sterilization, only means of disinfection
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boiling

Tyndalization

steaming at 100C for 30 min. on each 3 successive days.
After heating, the medium is incubated to allow spores to germinate and vegetative organisms to grow which will be killed by the second steaming; the 3rd heating is a safety precaution .

used for culture media containing sugar or gelatin.

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Autoclaving (At a temperature above 100Co)

Steam under increased pressure, this is called (autoclaving) Under autoclave conditions, pressurize steam KILLS bacterial spore, vegetative cells and other microbial forms.

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The 2 common sterilization temp.

121Co for 15 min for sterilizing items such as media, liquid and medical instruments.
sterilized at 132Co for 30-60 Min. Infectious waste such as unused portion of patients’ specimens, patients’ culture, sharp disposable, sharp instruments such as scalpels, needles.

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used in commercial purpose to sterile high quantity of pre packed material

a) Direct sun light kills vegetative organisms rapidly, but spores are much more resistant.

b) Non ionizing radiation (Ultra violet light) is commonly used to sterilize the air in the surfaces (used in Bacteriological hood).

c) Ionizing radiation includes Gama rays, X-rays are used for sterilizing disposal such as gloves catheter, plastic syringe and Petri dishes.

d) Infrared radiation: by electrically heat element at temp180 C can be attained. Used for glassware.

V) Sterilization by radiation

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Used for sterilizing sera, solutions of sugars, vaccines, antibiotics and toxins …etc.

Filtration is commonly the mechanical operation which is used for the separation of microbes from fluids (liquids or gases) by interposing a medium through filters which only the fluid can pass.

VIII) FILTRATION TECHNIQUE

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تم بحمد الله وعونه

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