1. MOIST HEAT STERILIZATION
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2. Principle-Denaturation & coagulation of
proteins due to the latent heat present in
steam
Advantages of steam –Latent heat liberated
on condensing on a cooler surface increases
the temprature of that surface
What is Moist heat Sterilization?
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3. Types of Moist heat Sterilization
• Pasteurization
• Inspissation or Fractional Sterilization
Hot water below
boiling point
• Tyndallization or Intermittent
Sterilization
Boiling water
/steam at atm pr
• AUTOCLAVESaturated steam
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4. Pasteurization
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• 63 C for 30
minutes
Holder
Method
•72 C for 15-
20 seconds
Flash
Process
Heat labile fluids may be disinfected

5. It is the process of
thickening by dehydration
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Inspissation
 Media such as
Lowenstein –Jensen
media and Loeffler’s
serum are rendered
sterile by heating at
80-85 C for half an
hour on three
consecutive days

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Tyndallisation
Principle: The first exposure kills all
vegetative bacteria and the spores
since they are in a favourable
medium will germinate and be killed
on subsequent occasions
Though generally adequate this
method may fail with spores of
certain anaerobes and thermophiles

7.  The Autoclave was invented by Charles
Chamberland in 1879
AUTOCLAVE
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8. Definition
Autoclave is a pressurized
device designed to heat
aqueous solutions above
their boiling point at
normal atmospheric
pressure to achieve
sterilization
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9. Reliable sterilization with moist heat requires
temperatures above that of boiling water.
These high temperatures are most commonly achieved
by steam under pressure in an autoclave. .
Need for autoclaving:
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Autoclaving is the preferred method of
sterilization unless the material to be
sterilized can be damaged by heat or
moisture

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Liquid H2O cannot be
heated above 100°C in an
open vessel
At 100°C boils
H2O heated in a sealed vessel
Pressure rises
Boiling point of H2O is raised

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Air removal
Downward displacement
Steam pulsing
Vacuum pumps
Superatmospheric
Subatmospheric
Process

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13. Biological indicators are the only process indicators that directly monitor the lethality of a
given sterilization process. Spores used to monitor a sterilization process have
demonstrated resistance to the sterilizing agent and are more resistant than the
bioburden found on medical devices.
Bacillus stearothermophilus
Thermophilus aquaticus
Spore Test
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If the autoclave does not reach the
right temperature the spores
will germinate when incubated and
their metabolism will change the
color of a pH –sensitive chemical.

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Any Questions???

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