Download Heat sterilization

Sterilization: complete removal, destruction,
inactivation of all forms of microbial life
viruses,
Fungi,
bacteria,
Spores.
• Disinfection: elimination of most pathogenic
organisms excluding sporicidal activity. There
are 3 levels;
• HLD, all vegetating bacteria, MTB, fungi, all
viruses
• ILD, all vegetating bacteria, MTB, majority
of fungi, majority of viruses
• LLD, vegetating bacteria except MTB,
some fungi, some viruses
•Antiseptics: chemical disinfectants applied to
skin, mm but not systemic
•Cleaning: removal of dust, dirt, organics, FM.
•Decontamination: general term applied to any
procedure by which microorganisms are
reduced to a level where items are safe to
handle
Patient’s care items are divided into 3
categories:
Critical items
Semi-critical items
Non-critical items
Depending on the risk of infection due to their utilization
Critical
Semi critical
Items enter -sterile
tissues-cavitiesvascular system
Items come in
contact with
intact mm &
non intact skin
e.g. needles,
implants, catheters,
surgical instruments
e.g. endoscopes,
endotracheal tube,
thermometer
Sterilization: EO,
autoclave,
plasma, sterilant
High level disinfectant,
glutaraldehyde, chlorine
active, hydrogen
peroxide
Noncritical
Items come in
contact with intact
skin
e.g.
sphygmomanometers,
bed linens, floors
Intermediate and low
level disinfectants,
alcohols, phenols
Decreasing order of resistance of microorganisms
to disinfection and sterilization
Resistant
•
•
•
•
•
•
•
Susceptible
•
•
Prions
Bacterial spores
Mycobacteria
Small non-enveloped
viruses
Gram-negative bacteria
Fungi
Large non-enveloped
viruses
Gram-positive bacteria
Lipid enveloped viruses
Decontamination Steps
I. Heat
1- Moist heat or steam sterilization
2- Dry heat sterilization
II. Low temperature (cold):
1. chemical
a. ethylene oxide
b. liquid steriliants: GLD, PAA, H2O2
2- plasma sterilizer
III. Other sterilizers:
1- ionizing radiation
2- filtration
3- microwaves; in pharmaceutical industries
• Heat is the most practical, efficient, and
inexpensive method of sterilization and
disinfection of objects that can withstand high
temperatures.
• There are two forms:
– Moist heat is much more efficient than dry heat because:
• it kills microorganisms by coagulating and denaturing
their enzymes and structural proteins
• it is quicker in heating up the article to be sterilized.
– Dry heat is believed to kill microorganisms by causing
destructive oxidation of essential cell constituents.
Autoclave = saturated water steam under high pressure.
heating water under controlled conditions in a closed vessel in order
that boiling point of water rises above 100°C.
Saturated steam carries the same temperature of boiling water.
It is essential to make steam saturated and free of any residual air because
air acts as an insulator, reduces temperature and hinders penetration.
Sterilization temperature and exposure time :
at 121°C for 20-30 minutes at double atmospheric pressure (2 bar)
or at 134°C for 3-6 minutes (at 3 bar).
• Steam sterilization is
the most common and
preferred method for
sterilizing those items
that can withstand high
temperature and
moisture, e.g. culture
media, surgical
instruments and
dressings.
Autoclave:
Advantages:
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Non-toxic
liberation of latent heat due to condensation of steam
Inexpensive
Rapidly microbicidal
Least affected by organic/inorganic soils
Rapid cycle time
Penetrates medical packing, device lumens
Disadvantages:
1- Deleterious for heat labile instruments
2- Potential for burns not for powders and oils
Sterilization monitored routinely by
combination of mechanical,
chemical, and biological parameters
• Physical - cycle time, temperature,
pressure
• Chemical - heat or chemical sensitive
inks that change color when
germicidal-related parameters
present
• Biological - Bacillus spores that
directly measure sterilization
(Geobacillus stearothermophilus)
Chemical Indicators