2. Physical method
1. Sunlight
a.Due to ultraviolet and heat ray kill the germs (germicidal).
b. Bacteria suspended in water are destroy.
c.Used to sterilized
Blankets, beddings, cloths, utensils, bad pan etc.
d. Typhoid bacilli killed
2. Drying
Moisture is essential for growth of bacteria. So, drying can destroyed Bacteria.
3. Heat
Most reliable method of Sterilization.
1. Dry heat
This method is used to Sterilized. Dry heat method is killing the effect of microorganisms due to -
1. Protein denaturation
2. Oxidative damage
3. Toxic effect of electrolytes/ damage metabolic activity.
Dry heat includes following method of Sterilization;
1. Red hot
This method is used to Sterilized;
1. Inoculating loop and wire
2. The tip of forceps
3. Spatulas
For example; Red hot method is used in needle destroyer instrument.
2. Flamming
It is useful in;
a. Sterilization of glass slides
b. Mouthbof culture tube
3. Incineration
Incineration is the process of complete burning of disposable waste and biomedical waste in an electric furnace known as incineration.
It is best method to decontaminate the destroying material and disposable of biomedical wastes.
It is useful in disposable of;
1. Soiled dressings, rags and swabs.
2. Solid paper and mouth wipes
3. Animal carcasses
4. Human anatomical waste
5. Pathological material
4. Hot air oven
Water; Holding period of 160 degree Celsius for one hours is used to Sterilize;
1. Glassware and all glass syringe
2. Forceps, scissors and scalpels
2. Moist heat
Methods are given below;
1. Temperature below 100 degree Celsius
a. Pasteurisation/Sterilization of milk
Milk heated 63 degree celcius for 30 minutes, cooling quickly at 13 degree Celsius or lower.
All nonsporing pathogens such as mycobacteria, brucella and salmonella are destroyed.
b. Vaccine bath
60 degree for hours.
c. Infective serum or body fluid
1 hours at 56 degree Celsius
d. Killing microorganisms
a. All mesophic non sporing bacteria are killed by exposure to moist heat at 60 degree celcius for 30 minutes.
b. Staphylococcus aureus and streptococcus fecalis required 60 minutes.
c. Temperature of 80 degree Celsius for 5-10 minutes destroy vegetative form of bacteria, yeasts, and moulds.
2. Temperature at 100 degree Celsius
1. Boiling
Vegetative formof bacteria are kill almost at 100 degree Celsius.
Uses;
a. Useful in Sterilization of needles, instruments, syringes, contaminated dishes.
b. Used for distruction of certain fungi, viruses, and bacteria.
2. Steam at atmospheric pressure (100degree celcius)
100 degree Celsius for 20 minutes on 3 successive day in used.
3. Steam under pressure/ temperature above 100 degree Celsius/Autoclave
Method by steam under pressure is most widely used. Effective and most reliable method of Sterilization. It has more penetrating power.
It destroy microorganisms including their spores.
Working of Autoclave
Sterilization by steam under pressure is generally carried at;
Temperature in between 108- 147 degree Celsius.
a. Pressure; 15lb
b. Time for 25-20 minutes
c. At temperature 121degree celcius
Uses;
By using appropriate temperature, pressure and time. Materials can be Sterilized;
a. Dressing and instrument
b. Laboratory ware and media
c. Pharmaceutical product
Steam Sterilizers (Autoclaves) in use;
a. Medical lab; sterile medical, surgical equipment
b. Laboratory autoclaves; glassware
c. Bowl and instrument Sterilizers
d. Rapid cooling Sterilizers
e. Decontaminate specific biological waste before disposable
f. Used for Sterilization of culture media.
Plastic tube, pipette tips, plastic container
g. Hospital dressing Sterilizers (108degree celcius)
3. Filtration
1. Candle filters
2. Asbestos filter
3. Sintered glass filter
4. Membrane filter
Used for sterilization of liquid substances or fluid.
Used for seperation of bacteriophages and bacterial toxin from bacteria.
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