Sterlization & Disinfection Lecture Notes PDF

Level (1) - Semester (1) MICROBIOLOGY D R Z I A D M A LECTURE (6) H A N STERILIZATION & DISINFECTION A -  It is the freeing of an article from all forms of life (microorganisms and bacterial spores).  Sterilization is an absolute term, i.e., the article is eithe...

Level (1) - Semester (1) MICROBIOLOGY D R Z I A D M A LECTURE (6) H A N STERILIZATION & DISINFECTION A -  It is the freeing of an article from all forms of life (microorganisms and bacterial spores).  Sterilization is an absolute term, i.e., the article is either sterile or not.  Bacterial spores are more resistant to heat and chemical, so they need standard methods (enough in capacity and time) to kill them.  It is the process of reducing the number of contaminating organisms to a level that cannot cause infection.  Some organisms and bacterial spores may survive.  Some items are not suitable for sterilization methods so they may be disinfected.  Items like:  Surgical gloves,  Surgical dressings  Surgical instruments,  Others  Should be sterile to prevent introducing microbes to the operation site.  Items like:  Samples collected,  Reagents  Culture media,  Should be sterile to get the sure correct diagnosis.  Should be sterile not to carry infections instead of treatment. -  -  Heat is most effective and a rapid method of sterilization and disinfection.  Excessive heat acts by coagulation of cell proteins.  Less heat interferes with metabolic reactions.  Heating above 100°C ensures killing of bacterial spores. A. Moist heat: heating in the presence of water or steam. B. Dry heat: heating in the presence of air.  Heating will kill the microbes by: a) Protein denaturation, b) Oxidative damage, c) Toxic effect of elevated electrolyte (dry heat).  Examples: ① Red heat for the bacteriological loop. ② Flaming for mouths of tubes. ③ Incineration of medical and dangerous waste in incinerators. ④ Hot air oven. -  It is one of the most common methods used for sterilization.  For sterilization, a temperature of 160°C is maintained (holding) for one hour at least.  Items sterilized in hot air oven can be:  Glass wares,  Surgical instruments,  Powder  Oily substances ① Put all instruments then start. ② Calculate time after reaching the wanted temperature. ③ Time of sterilization depends on the degree.  E.g. 160°C → 2 hours, 180°C → one hour. ④ Never put dirty instruments in the oven. - °  Boiling in water at 100°C for 30 minutes is done in a water bath to kill many microbes.  Glass tubes, rubber goods and surgical instruments may be disinfected by this method if you have no other way.  Water itself may be boiled to be used as drinking water.  Steam (100°C) is more effective than dry heat at the same temperature because: ① Bacteria are more susceptible to moist heat, ② Steam has more penetrating power, and ③ More heat is given up during condensation. °  Autoclave is a method of sterilization depending in applying pressure to make water boils at higher temperatures.  When the autoclave is closed and made air-tight, water starts boiling, and the inside pressures increases.  At 2 atmospheric pressure, water boils at 121°C. - ° ° 20 minutes 3-4 minutes. Biological Method:  Spores of Bacillus stearothermophilus:  Spores withstand 121°C heat for up to 12 min.  Strips containing these bacteria are included with the material being autoclaved, then cultured between 50°C and 60°C for surviving spores.  If spores are killed autoclaving is good. ▪ Unwrapped solid instruments for immediate use. ▪ Medical Surgeries ▪ Suitable for naked and single ▪ Podiatrist wrapped solid and hollow ▪ Tattooist items. ▪ Body Pierces ▪ Unwrapped & wrapped solid ▪ Dentists and hollow instruments. ▪ Plastic surgeons ▪ Porous loads, e.g drapes & ▪ Day surgeries gowns. ① Put all instruments then start. ② Use only distilled water. ③ Never open until P is becoming normal. ④ Never put dirty instruments in the autoclave. ⑤ Check the sterilization indicator at the end of the process. ⑥ Write the date and time of sterilization on each package. - - -  Gamma rays,  Infrared.  X-rays,  Ultraviolet light.  Beta rays from radioactive materials.  Cause death or mutations in  Damages DNA which causes microorganisms as they damage the mutations or death. DNA and proteins. ① Most effective on actively ① Used to sterilize heat-sensitive multiplying organisms. materials including medical ② Most commonly used as UV- equipment, disposable surgical lamps that destroy microbes in supplies and drugs. the air in operation rooms, ② Radiation can be carried out after special laboratories or drinking packaging. water.  Damages skin, eyes.  Does not penetrate paper, glass, and cloth.  -  Mild forms of disinfectants.  Chemicals that are used for disinfection.  Used externally on living tissues to kill microorganisms,  Used only on inanimate (non- living)  E.g.: on the surface of skin and mucous objects. membranes.  Can harm living beings, and more toxic  Will not harm living tissues than antiseptic.  To be used for surface cleaning, flooring,  Topical anti-infective agents are tabletops, doorknobs, switches, extensively used in surgery for: handles, bathrooms, WC etc. ① Antisepsis of the surgical site  Mode of action: denaturation of ② Surgeon's hands intracellular protein, alteration of ③ Disinfect surgical instruments. cellular membranes (often through  Antiseptics also have been used to treat extraction of membrane lipids), or local infections. enzyme inhibition.  Disinfectants should be nondestructive  Antiseptic preparations should not be to applied surfaces. toxic to the host tissues and should not  Offensive odor, color, and staining impair healing. properties should be absent or minimal.  Kills microorganism & prevents their  Destroys microorganisms. growth. Sometimes the same compound may act as an antiseptic and a disinfectant, depending on:  The drug concentration,  Conditions of exposure,  Number of organisms, etc. To achieve maximal efficiency: it is essential to use the proper concentration of the drug for the purpose intended. -  - Clinical Case  Grandfather Ali visited a doctor. The doctor prescribed fluids, injections and asked for investigations. A nurse came, collected blood sample using a syringe, and put the blood in sterile tubes. The nurse also inserted an intravenous line and gave Grandpa fluids. After about one week the doctor visited him again and found enlarged lymph nodes and he asked for biopsy. A man came, cleaned the skin with alcohol, made incision by a surgical instrument, took a sample and closed the wound by sutures and put a sterile dressing. ① What is the method of sterilization of syringes? ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ② How were glass test tubes sterilized? ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ③ Do you think medical fluids are sterile or not? ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ④ What disinfectant was used for skin? Do we use another term for it? ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ⑤ How to sterilize surgical instruments? ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..…………..  - Assignment If you have an endoscope composed of different parts made from different materials, how to sterilize it? Summary ① Sterilization and disinfection aim to get rid of microbes outside the human body. ② Sterilization is absolute while disinfection has degrees. ③ Methods of sterilization include physical and chemical methods. ④ Physical methods may be using heat, filtration or radiations. ⑤ Chemical agents are called disinfectants or antiseptics.