Lab.1 Sterilization and Disinfection PDF

‫ هختبر البكتريولوجي‬/‫الورحلة الثانية‬ Lab.1 Sterilization and Disinfection Sterilization: destruction or killing of all living organisms including the highly resistance spore. In bacteriology, surgery and medicine, sterilization of instruments, drugs and supplies is important f...

‫ هختبر البكتريولوجي‬/‫الورحلة الثانية‬ Lab.1 Sterilization and Disinfection Sterilization: destruction or killing of all living organisms including the highly resistance spore. In bacteriology, surgery and medicine, sterilization of instruments, drugs and supplies is important for the prevention of infection. Types of sterilization: 1. Physical methods A. Heat 1.Dry heat a. Red heat: e.g. heating of loop, points of forceps, needled and mouth of culture tube …etc. b. Hot air oven: temperature of 160 °C for 1 hour and half or 180 °C for 1 hour are employed. Hot air oven is the best method for sterilization dry glassware, forceps, powders … etc.  2. Moist heat a- At a temperature below 100 °C : example pasteurization of milk, the temperature employed either 63-66 °C for 30 min. or 73 °C for at least 15 seconds. This will kill all non-spore forming pathogens such as B. abortus and various salmonellae. b- At a temperature of 100 °C : 1. Boiling at 100 °C for 5-10 min. this is sufficient to kill all non-spore forming and many but not all spore M.O., used to sterile water. 2. Steaming at 100 °C example Tyndallization which involves steaming for 30 min. on each 3 successive days. After heating, the medium is incubated to allow sores to germinate and vegetative organisms to grow which will be killed by the second steaming. The 3rd heating is a safety precaution. Used for culture media containing sugar or gelatin. c- At a temperature above 100 °C: steam under increased pressure this is called (autoclaving). This is the usual method of sterilization bacteriological media, surgical instruments,..etc. The minimum values required for sterilization in an efficient autoclave are 15lb/inch² at 121 °C for 15 min. B.Radiation: act on nucleic acid, used in commercial purpose to sterile high quantity of pre packed material e.g. disposable syringe, catheter. 1. Direct sun light kills vegetative organisms rapidly, but spores are much more resistant. 2. Ultra violet light is commonly used to sterilize the air in the hospital operating rooms. It has no effect on under surfaces. 3. Ionizing radiation includes high speed electrons. X-rays. It has effect on under surfaces. C. Filtration: to render fluids, including bacterial culture, free from bacteria by passing them through special filters, ex: Seitz filter. This method is used in sterilizing liquids that would be damaged by heat such as serum, vaccines, antibiotic solutions, sugars. 2. Chemical methods is act on lipid content of cell membrane, denaturation of protein, and on nucleic acid, it either kill or stop the growing of M.O. we had 2 types; A- Disinfectant is toxic and corrosive for living tissue so it’s used for non-living surfaces like floor.  Phenol group: contain benzene ring used for bathrooms, hospital floor.  Chlorine: treatment of swimming pools. B-Antiseptics is less toxic and can be applied to living tissue (skin)  Detol  Chlorhexiden: used to treat surgical wounds because it works on both G –ve and G+ve.  Iodine :used in surgery to sterle skin pre- operation.  Soap and detergent.  Alcohol at con. 70%.