Sterilization and disinfection
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Brief description of applications of sterilization and disnfection in routine healthcare
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Sterilization and disinfection
- 1. STERILIZATION AND DISINFECTION Dr Meher Rizvi Department of Microbiology & Immunology College of Medicine & Health Sciences
- 2. Objectives Define the terms Sterilization, Disinfection and Antisepsis Appreciate various physical and chemical methods for control and prevention of bacterial infection
- 3. Definitions : Sterilization : • Complete killing or removal of all forms of living micro- organisms including spores from an article or medium Disinfection : • Destruction of most pathogenic organisms from a site but not bacterial spores Antisepsis: • Process designed to kill or inhibit microorganisms present on the skin Reduction of 106 log colony forming units Reduction of 103 log colony forming units
- 4. Overview of Sterilization/Disinfection methods Physical methods • Heat : Dry; Moist • Filtration • Radiation Ionizing radiation Nonionizing radiation Chemical methods • Alcohols • Aldehydes • Phenolic compounds • Halogens • Oxidizing agents • Gas sterilization Gamma rays Ultraviolet rays Hydrogen peroxide Peracetic acid Ethylene oxide Plasma sterilization
- 5. STERILIZATION Heat Autoclave: Wet heat Hot air oven: Dry heat
- 6. Dry heat Flaming Hot Air Oven Mechanism of action: Charring, Protein denaturation, Oxidative damage
- 7. Hot air oven: Dry heat • Electrically operated • Heaters at the bottom • Fan to circulate the hot air • Thermostat • Temperature: 1600C for two hours. • Materials sterilized: • Sterilization control: Biological indicator Holding time?? Glassware: Petridishes, flasks, test tubes Surgical instruments: scalpels, forceps Chemicals: Paraffin, glycerol 106 spores Bacillus subtilis subspp. niger
- 8. Moist heat • Pasteurization • Boiling • Autoclave Mycobacteria, brucella and salmonella are killed Temperature: 630C to 720C Temperature: 100 0C Time 15 minutes Does not kill spores Temperature: 121 0C Pressure: 15 pounds Time: 15 minutes Kills 106 spores Biological indicator: Geobacillus stearothermophilus Not suitable: surgical instruments Kills bacteria, viruses, spores
- 9. Materials sterilized: Surgical instruments Culture media, Linen Plastic ware Solutions and water Biohazardous waste Mechanism of action: Protein denaturation, Coagulation of proteins
- 10. Temperature: 121 0C Pressure: 15 pounds Holding time: 15 min
- 11. STERILIZATION Filtration Millipore filter Filter heat labile solutions Vaccine Antibiotics Toxin Pore size: 0.22µm -0.45µm
- 12. Filtration of air 3 ply Surgical mask 50% efficiency N 95 mask > 0.3µm 95% efficiency High Efficiency Particulate Air Filter HEPA > 0.3µm in Laboratory Lamellar flow Operation Theatre
- 13. STERILIZATION Gamma ray MOA: Breakage of DNA Use: Syringes, infusion sets, Ultraviolet rays Use: Disinfection of clean OT surfaces/wards/labs No change in temperature: Cold sterilization NON-IONISING RADIATION RADIATION IONISING RADIATION
- 14. GASEOUS STERILIZATION Ethylene oxide High penetrability. MOA: Combines with cell protein Highly inflammable, irritant, carcinogenic Diluted ( 10-20%) with inert gases i.e. 700mg/L Requires 40-50% humidity; 380C x 8hrs Extensive aeration essential Control: Bacillus globigi Use: Plastic ware, heart lung machines, respirators
- 15. Plasma sterilization Principle: Gaseous state of ions (photons/electrons) kill micro-organisms and spores efficiently Chemical sterilants: H2O2 and peracetic acid used at low temperatures Reactive free radicals are produced from the hydrogen peroxide vapors by using microwaves or radio waves in a vacuum An efficient method. Does not produce toxic byproducts- has replaced ethylene oxide for surgical instruments Control: Geobacillus stearothermophilus
- 16. CHEMICAL AGENTS OF STERILIZATION/DISINFECTION Low level of disinfectant Intermediate level of disinfectant High level of disinfectant Chemical sterilant
- 18. • MOA: denature proteins – rapidly kill bacteria Inactive against bacterial spores • 70-90% ethanol or isopropyl alcohol ( 90-95% ) used for decontamination of skin before venipuncture • 100% alcohol is ineffective in killing bacteria since it cannot penetrate – water molecules required to transport alcohol into bacteria
- 19. DISINFECTION Aldehydes Formaldehyde Gluteraldehyde Ortho-phthalaldehyde Bactericidal Fungicidal Sporicidal CHEMICAL STERILANT HIGH LEVEL DISINFECTANT
- 20. MOA: Inactivate Nucleic acids and proteins • Use: Anatomical specimen presevation, fumigation,toxoid preparation • Disadv:Toxic, irritant when inhaled, corrosive to metals Formaldehyde 40% • Advantages: Less toxic, irritant and corrosive • Use: Sterilization of Endoscopes, cystoscopes, bronchoscopes, nebulizers • Disadv: Needs activation, Active for 14 days Gluteraldehyde 2% x 20 min Spores: 12 hrs • Advantages: More stable, no activation needed, ↑M. tuberculosis activity , better odor • Use: Sterilization of endoscopes, cystoscopes Ortho-phthaldehyde OPA 0.55%
- 21. OXIDISING AGENTS Hydrogen peroxide Peracetic acid High level disinfectant Chemical sterilant
- 22. MOA: Toxic free radicals attack lipids and DNA • Use: High level disinfection: Ventilators, tonometers, wound dressing • Adv: Unaffected by organic matter. Enhances removal of organic matter from equipments, safe, not carcinogenic H2O2 3-6% • More active than H2O2 • Use: High level disinfection: Haemodialysers, endoscopes • Disadv: Corrosive Peracetic acid 1%
- 24. MOA: Oxidize cell constituents • Use: Skin antiseptic • Disadv: Allergy, yellow stain Iodine tincture 2% • Use: Pre-operative skin antisepsis, wound cleaning • Adv: Stable, non staining, released slowly Povidone iodine • Use: Good Laboratory disinfectant. Kills bacteria, viruses, fungi • Disadv: Organic matter ↓ activity, carcinogenic, corrosive Chlorine Sodium hypochlorite (5.25%) Calcium hypochlorite
- 25. Antisepsis : • Alcohols : • excellent activity against all organisms: denature proteins • cannot kill spores • non toxic to human tissue Decontamination of skin before surgery • Povidone-Iodine (halogen) • Chlorhexidine (phenolic)
Editor's Notes
- Holding time: Time for sterilization ( say 2 hours ) to be measured from when the required temperature (1600C ) is achieved. Browne’s tube: It contains a Heat sensitive red dye which turns green if adequate temperature is achieved for a definite period of time.
- Holder’s method: 630C for 30 min; Flash method: 720C for 20 sec followed by rapid cooling to 130C or lower
- Ultraviolet light : kills bacteria by damaging DNA. has a poor penetration power, hence used to sterilize small areas and surfaces. sterilization of laboratory working surfaces , and air in any critical area of hospital Ionising radiations : gamma rays – have higher penetration power than UV light. kill bacteria by damaging DNA. used for sterilization of disposable surgical supplies like gloves , plastic syringes, specimen containers, some foodstuffs
- Uses: dental equipments, syringes, petri dishes,sutures, catheters
- Chlorine: