2. Sterilization
• Is complete freeing of an article from all living
organisms including bacteria and their spore
toxin,viruses, fungi and their spores.
• Absolute term
• Physical methods <
9. • Red heat: Articles such as bacteriological
loops, straight wires, tips of forceps
• By holding them in Bunsen flame till they
become red hot
• Flaming: This is a method of passing the
article over a Bunsen flame
• mouth of test tube,culture media, flasks, glass
slides and cover slip
10. How to use the hot air oven
160 c
60 min (holding time)
Metals (forceps, scissors, glassware (such as Petri-dishes, pipettes, flasks,
swabs, oils, grease, petroleum jelly
How to test the efficiency of the hot air oven:
1- Brown’s tube NO.3
Contain chemical substance with red solution ,if sterilization is proper it will
changed into green
2- Adhesive tape
At the end of sterilization the lines
In the tape change from coulerless or whit
Into black
16. At 100 ⁰c:
• 1. boiling at 100 ⁰c
Kills only non sporing bacteria
• Steaming at 100 ⁰c Arnold’s,Koch’s steamers
- single exposur -90 min
- intermittent exposur (Tyndallization):
Exposur to the steam of boiling water (100
-30 min) for three succesive days
Kills both sporing and non –sporing bacteria
17. Above 100 ⁰c - Autoclave
• Principle :
• Heat under pressure 121 c
15 b/I
15 min
• How to use the autoclave
• How to test the efficiency of autoclave:
1- brown’s tube NO.1
2- Adhessive tabe
3- Biological (Bacillus sterothermophilus)
21. Classification of disinfectants:
1. Based on consistency
a. Liquid (E.g., Alcohols, Phenols)
b. Gaseous (Formaldehyde vapor, Ethylene oxide)
2. Based on spectrum of activity
a. High level
b. Intermediate level
c. Low level
3. Based on mechanism of action
a. Action on membrane (E.g., Alcohol, detergent)
b. Denaturation of cellular proteins (E.g., Alcohol,
Phenol)
c. Oxidation of essential sulphydryl groups of enzymes
(E.g., H2O2, Halogens)
e. Damage to nucleic acids (Ethylene Oxide,
Formaldehyde)
22. • Phenol and derivatives: Act by disruption of
membranes, precipitation of proteins and
inactivation of enzymes
• Alcohol : dehydrate cells, disrupt membranes and
cause coagulation of protein
– 70% Ethanol- antiseptic on skin.
• Halogens: They are oxidizing agents and cause
damage by oxidation of essential sulfydryl groups
of
• enzymes.
– Iodine
– Chlorine
23. Heavy Metals:Act by precipitation of proteins
_ Silver nitrate
• Gas
- Ethylene Oxide-killing spores rapidly.
plastics, syringes, disposable petri dishes,
Aldehydes:
damages nucleic
acids. It kills all microorganisms, including spores
Glutaraldehyde and 40% formaldehyde
operation theatres, biological safety cabinets, wards,
24. • Bacteriostasis is a condition where the
multiplication of the bacteria is inhibited
without killing them.
• Bactericidal is a condition where bacteria is
killed or inactivated.
