Sterilization LAB 2 A L NOOR AMEER What

Sterilization LAB. 2 A. L. NOOR AMEER

What sterilization mean? Sterilization is the destruction or removing of all living microorganism. Advantages of sterilization: 1 - Prevent food spoilage 2 - Prevent human, animal and plant infections 3 - Prevent microorganisms interference during industries 4 - Prevent contamination of pure culture used in laboratories and industries.

Antimicrobial agents: Substances are classified as: Disinfectants, Antiseptics and Chemotherapeutic agents Disinfectants: -substances used to eliminate or destroyed the microorganisms (excluding bacterial spores), used for treating inanimate objects and materials (such as Alcohols, Phenols, … etc. ) Antiseptics: - substances used to eliminate bacterial infection, these agents used on the skin and other living tissue (such as Detol, Septol, …. etc. ) Chemotherapeutic agents: - antimicrobial substances administered systematically for the treatments of an infection, it may be baceriostatic or bactericidal in its action (such as antibiotics)

Methods of Sterilization 1 - Physical method 2 - Chemical method 3 - Mechanical method

1 - Physical method: 1 - Heat: a) Dry heat sterilization: the direct heat by flame of the burner (for metal tools such as loop, needle, …. . ) or by oven (hot air) to sterilize the glassware's, (the temperature is 180 Co for 1 &1/2 hours). b) Wet (moist) heat sterilization: by autoclave (121, 15 pound/inch 2 for 1030 min. ) this method used for sterilization the culture media. The killings take place by protein denaturation.

c) Tyndallization: by boiling 100 Co/ 30 min. for 3 days for killing vegetative cells and spores specially in sugar liquid media (which affected by high temperature in autoclave). d) Pasteurization: heating the liquids (milk) (63 Co for 30 min. or 72 Co for 15 sec. ) for killing vegetative cell of Mycobacterium tuberculosis and Brucella.

2 - Radiation: two types of radiation are used: (a) non-ionizing. (b) ionizing. a) Non-ionizing radiation : use of longer wavelength and lower energy, as a result loses the ability to penetrate substances, and can only be used for sterilizing surfaces, such as UV ray b) Ionizing radiation: is the use of short wavelength, highintensity radiation to destroy microorganisms such as gamma or X-rays which are used for sterilization of disposable items.

3 - Chemical methods of sterilization: substances such as: Halogens, Phenols, Alcohols, Formaldehyde, used to sterilize many objects (heatsensitive solid objects) and their effect is depend on the concentration, time, type of M. O. PH, temperature, …. . etc.

3 - Mechanical methods of sterilization: Filtration a- Seitz filters: Asbetose filters used for removing bacteria from liquids with heat- sensitive substances. b- Membrane filters: Nitrocellulose filters used in microbiological examination of water because its prevent the passing of bacteria and viruses.