1. Sterilization
Lab 3
Abeer Saati

2. Sterilization
Sterilization is a term referring to any process that eliminates (removes) or kills all forms of microbial life, including transmissible agents (such as fungi, bacteria, viruses, spore forms) present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media.

3. CLASSIFICATION OF METHODS
Sterilization and disinfection are done by:
(A). Physical methods
1.   Heat      2.   Radiation
(B). Chemical methods
(C). Mechanical methods

4. (A) Physical methods
1.Sterilization by heat:- Heat is most effective and a rapid method of sterilization and disinfection. Excessive heat acts by coagulation of cell proteins. Less heat interferes metabolic reactions. Sterilization occurs by heating above 100°C which ensure lolling of bacterial spores. Sterilization by hot air in hot air oven and sterilization by autoclaving are the two most common method used in the laboratory. Types of heat : A. Sterilization by moist heat B. Sterilization by dry heat

5. (A) Physical methods
A. Sterilization by Moist Heat Moist heat acts by coagulation of protein, breakage of DNA strands, and loss of functional of cell membrane.
Sterilization above 100°C: (Autoclaving)
Autoclaving is one of the most common methods of sterilization. Principle: In this method sterilization is done by steam under pressure. Steaming at temperature higher than 100°C is used in autoclaving. The temperature of boiling depends on the surrounding atmospheric pressure. A higher temperature of steaming is obtained by employing a higher pressure. When the autoclave is closed and made air-tight, and water starts boiling, the inside pressures increases and now the water boils above 100°C. At 121°C temperatures is obtained. This is kept for 15 minutes for sterilization to kill spores. It works like a pressure cooker.

6. (A) Physical methods
B. Sterilization by Dry Heat Dry heat at 160°C (holding temperature for one hour is required to kill the most resistant spores). The articles remain dry. It is unsuitable for clothing which may be spoiled.
--Red Heat. Wire loops used in microbiology laboratory are sterilized by heating to 'red' in bunsen burner or spirit lamp flame. Temperature is above 100°C. It leads to sterilization Sterilization by Hot Air Hot Air Oven (Sterilizer). It Is one of the most common method used for sterilization. Glass wares, swab sticks, all-glass syringes, powder and oily substances are sterilized in hot air oven. For sterilization, a temperature of 160°C is maintained for one hour. Spores are killed at this temperature. It leads to sterilization.

7. 2.Radiation sterilization:-
(A) Physical methods
2.Radiation sterilization:-
Methods of sterilization using radiation such as X-rays, gamma rays, or UV. The major target for these radiation is microbial DNA.
Gamma rays are very penetrating and are commonly used for sterilization of medical equipment, such as syringes, needles.
X-rays are a form of ionizing energy allowing to irradiate large packages for sterilization of medical equipment.
Ultraviolet light (UV) is useful only for sterilization of surfaces and some transparent objects.

8. (B). Chemical methods
Chemicals that destroy pathogenic bacteria from surfaces. Some chemical have very narrow spectrum of activity and some have very wide. Those chemicals that can be safely applied over skin and mucus membranes are called antiseptics

9. (B). Chemical methods 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. Damage to nucleic acids (Ethylene Oxide, Formaldehyde)

10. (C). Mechanical methods
Filtration does not kill microbes, it separates them out. Membrane filters with pore sizes between μm are commonly used to remove particles from solutions that can't be autoclaved. It is used to remove microbes from heat labile liquids such as serum, antibiotic solutions, sugar solutions, urea solution.
Different types of filters are:
Earthenware filters
Asbestos filters
Sintered glass filters
Membrane filters

11. Thank you