Definition: is the complete removal or elimination
of all transmissible agent such as bacteria & virus from surface, a piece
of equipment , food or biological culture, it used principally to prevent
spoilage of food and other substance and to prevent the transmission of
diseases by destroying microbes.
Methods of sterilization:
I)Physical
methods:
a. Temperature: cause kill microorganism by decomposed
cell wall or change the nature of its enzymes.
1.
High Temperature:
• Dry heat: used for kill
microbes in metallic, plastic & glass instrument.
• 160
for 2hr. or 170
for 1hr. add 30-35% of hydrogen
peroxide
• Rate of elevate Temperature=10-15
• Kill microbes
in acidic or high salt medium is higher than in medium contain lipid or protein
which protect microbes.
•
Moist heat: it is more effect than dry heat because
a. moist heat has highest penetration power in microbes.
b. not needs high temperature or long time for sterilization.
•
Used in pasteurization for
kill tuberculosis bacilli, E.coli and salmonella in milk.
• 72
for
15min. or 66
for 30 min.
Autoclaves:
it commonly use steam heated
to 121
•
at 103Kpaq
above atmospheric pressure for 15min.
·
Autoclaves will inactivate all fungi, bacteria, and virus also bacteria spores.
• Flaming: is done to loops and straight wires in
microbiological lab.
• Incineration: will burn any organism to
ash
·
It used to prevent spread of infection disease.
·
Used more than 500
for burn substance which have microbes.
- Tyndallization (or repeated boiling):
·
The solution boiling for 30min. → cool and save for time→ boiling (these
procedure repeat three time)
·
Disadvantage:
1. have long time.
2. Growth of spore may be altering
the medium.
2.
Low temperature: it causes:
·
Slow the chemical reaction specific reaction need to enzymes.
·
The cell wall become Rigid.
·
Inhibit metabolism by inhibit enzymes and stop growth.
b.
Filtration: removed
microorganism from liquid by small pores.
·
Used for thermo-label substances as blood serum, enzyme solution,
antibiotics and some bacteriological media.
No comments:
Post a Comment