بسم الله الرحمن الرحيم STERILIZATION Prof. Khalifa Sifaw Ghenghesh Dept. of Medical Microbiology, Faculty of Medicine, Tripoli University Tripoli - Libya

What is Sterilization? The removal of all forms of living material. Important: First Objects to Be Sterilized Should Be Cleaned by Washing.

METHODS OF STERILIZATION 1. DRY HEAT –Red Heat –Hot - Air Oven: 160 o / 60 minutes 180 o / 20 minutes 2. MOIST HEAT: –Tyndallization: > 100 o C/ 30 minutes On 3 Consecutive Days. –The Autoclave: > Pressurized Steam. 121 o C/ 1.1 bar for 15 minutes. 134 o C/ 2.2 bar for 3 minutes.

TESTS FOR AUTOCLAVE FUNCTION –The Bowie-Dick Autoclave Tape Test: –Browne's Tubes: –Automatic Controls or Pen Records: –Bacteriological Tests (Spore Tests):

2. IRRADIATION i. Ultra - Violet Radiation (UV): –a. Not Recommended. –b. Poor penetration in Air. –c. Suitable to Reduce Microbial Counts in Safety Cabinets. ii. Gamma - Ray Radiation –Source: Cobalt 60. – a. Lethal to All Forms of Microbial Life. –b. Used Commercially.

3. FILTRATION –Bacterial Stopping Filters. 4. GASES i. Ethylene Oxide Gas: –a. Ventilators. –b. Toxic & Explodes When Mixed with Air. ii. Formaldehyde: –a. Rooms and Lab. Cabinets.

5. LIQUIDES: –Disinfectants. i. Glutaraldehyde: –a. Sterilizing Heat Sensitive Pieces of Equipments.

Forms of Sterilization by Heat and Principle Uses. _______________________________________________________________ Type of HeatUse _______________________________________________________________ DRY: 1. Red Heat.Microbiological Loops. Incineration of Used Lab. Culture Plates. 2. Hot - Air Oven. Many Surgical & Dental Instruments but Not Fabrics or Rubber MOIST: 1. Steam at 100 o C Some Bacteriological Media. On 3 Consecutive Days. 2. Pressurized Most Surgical and Dental Instruments, Steam (Autoclave). Fabrics & Dressings (If Wrapped); Most Microbiological Media & Glassware. _______________________________________________________________

Heat Content of Water and Steam _______________________________________ Phase Temp. Heat Content (kJ/kg) of oC SensibleLatent Total WaterHeat Heat Heat Liquid Vapour Vapour Vapour _______________________________________

PROPERTIES OF STEAM –i. Moisture content –ii. Heat content –iii. Penetration

PRESSURE STEAM STERILIZERS 1. Porous Load Sterilizers (Prevacuum type): Removal of air and heating of the chamber. Sterilization of the load. Removal of steam and drying of the load by mechanical evacuation. Admission of filtered air to restoration atmospheric pressure.

2. Downward Displacement Jacketed Sterilizers: Gradual displacement of air by incoming steam while the chamber is heated to the selected sterilizing temp. Sterilization of the textile packs for 30 min/ 121oc. Drying of the load by partial vacuum. Restoration of the chamber to atmospheric pressure.

3. Unwrapped Instrument and Utensil Sterilizers: DSL autoclaves 4. Fluid Sterilizers: e.g. water, iv solutions, etc.

Factors influencing sterilization time for fluids: –rate of heating of the chamber: –type of container: –viscosity of the liquid: –volume of the liquid: –trapped air:

"بسم الله الرحمن الرحيم" DISINFECTION AND DISINFECTANTS Prof. Khalifa Sifaw Ghenghesh Dept. of Medical Microbiology, Faculty of Medicine, Al-Fateh University Tripoli - Libya

Disinfection The removal of most of the pathogenic microorganism, but often non-pathogenic or resistant forms of pathogens remain.

Methods of Disinfection A. Cleaning Instruments with high risk organic material >> Treat with strong disinfectant >> Cleaning >> Sterile or dispose of.

B. Disinfection by Heat i. Pasteurization ii. Boiling water iii. Flaming off alcohol C. Physical Methods Ultrasonics Ultrasonic vibration > Disrupte microorganisms e.g. Ultrasonic scalers.

D. Chemical Disinfectants Denaturing protein or lipid Act: Disrupting the biosynthetic pathways I. Phenols Clear phenolic solutions: Black and White Phenolic Compounds: Chloroxylenol: (Dettol) Hexachlorophane: Pre-operative scrub

II. Halogenic Compounds Hypochlorites: Effective > HBV Iodine + Alcohol Pre-operative skin antiseptic. Bovidone Iodine: an anti-plaque agent.

III. Aldehydes Formaldehyde Gluteraldehyde Alcohol Antiseptics Are bacteriostatic agents that can be used on skin and mucosal surfaces.

IV. Diguanides Chlorhexdine 0.5% + 70% alcohol >>> Skin disinfectant Chlorhexidine gluconate Treatment of oral candidosis + oral ulceration

V. Quaternary Ammonium Compounds Cetrimide VI. Organic Dyes e.g. gentian violet

Factors Affecting the Effectiveness of Disinfectants: Tests of the Proper Functioning of Liquid Disinfectants: " In-use" Tests.

Storage of Sterile Instruments Never store instruments in liquid disinfectants. Waste Disposal Special Problems HBV, HCV and HIV (AIDS)

Sterilization and Disinfection in Dentistry Sterilization >>> Autoclave. Dental instruments can and should be autoclaved after each patient. Nozzles of air and water spray: ??