Sterilization and disinfection. An Update

20,616 views
20,313 views

Published on

Sterilization and disinfection. An Update

3 Comments
55 Likes
Statistics
Notes
No Downloads
Views
Total views
20,616
On SlideShare
0
From Embeds
0
Number of Embeds
222
Actions
Shares
0
Downloads
2,278
Comments
3
Likes
55
Embeds 0
No embeds

No notes for slide

Sterilization and disinfection. An Update

  1. 1. STERILIZATION AND DISINFECTION AN UPDATE Dr.T.V.Rao MDDR.T.V.RAO MD 1
  2. 2. HISTORY • 1862 Invention of the Autoclave • 1880 The first indicator : a potato • 1906 Creation of the FDA • 1925 Waxy pellets that melt at 121oC • 1932 (ATI) CI with lead sulphite passes from black to white • 1940 (ATI) CI Chromium TriChloride passes from purple to greenDR.T.V.RAO MD 2
  3. 3. HISTORY (CONT) • 1960-70 Development of the Dvalue concept using heat resistant spores for sterilisation + Fvalue + Zvalue • 1965 Proposal by Sweden of the SAL for a definition of sterility • 1979 Proposal by Canada of a legal definition of sterilityDR.T.V.RAO MD 3
  4. 4. TERMINOLOGY IN STERILIZATION• Sterilization – a process that destroys all viable microbes, including viruses and endospores; microbicidal• Disinfection – a process to destroy vegetative pathogens, not endospores; inanimate objects• Antiseptic – disinfectants applied directly to exposed body surfaces• Sanitization – any cleansing technique that mechanically removes microbes DR.T.V.RAO MD 4
  5. 5. TERMINOLOGY IN STERILIZATION• Degermation – mechanically removing microbes form surface (skin) such as surgical hand scrubbing, or wiping skin with alcohol prior to venipuncture• Sepsis – bacterial contamination• Asepsis – absence of significant contamination• Bactericidal (microbicidal) - -cidal means kill• Bacteriostatic (micro biostatic) - -static means inhibition of growth and multiplication DR.T.V.RAO MD 5
  6. 6. AIM OF STERILIZATION - ASEPSIS Asepsis is the practice to reduce or eliminate contaminants (such as bacteria, viruses, fungi, and parasites) from entering the operative field in surgery or medicine to prevent infection. Ideally, a field is "sterile" — free of contaminants — a situation that is difficult to attain. However, the goal is elimination of infection, not sterility . • http://en.wikipedia.org/wiki/AsepsisDR.T.V.RAO MD 6
  7. 7. HOW STERILIZATION WORKS• Cell wall maintains integrity of cell • When disrupted, cannot prevent cell from bursting due to osmotic effects• Cytoplasmic membrane contains cytoplasm and controls passage of chemicals into and out of cell • When damaged, cellular contents leak out• Viral envelope responsible for attachment of virus to target cell • Damage to envelope interrupts viral replication • So…non enveloped viruses have greater tolerance of harsh conditionsDR.T.V.RAO MD 7
  8. 8. METHODS• Physical • Choice of method depends on practical issues such • Heat as ease of use or material • Filtration compatibility • Irradiation • Proctoscope need not be as free of contamination as an • Quarantine artificial heart valve• Chemical • Cleaning of objects needed before attempt at sterilization DR.T.V.RAO MD 8
  9. 9. FACTORS INFLUENCING ABILITY TO KILL MICROBES• Strength of the killing agent• Time that the agent has to act• Temperature of environment • rate of microbe death doubles with every 10˚C rise in temp.• Type of microbe• Environment around the area to be decontaminated• Number of microbes to be killedDR.T.V.RAO MD 9
  10. 10. “IDEAL” STERILIZATION METHOD• Highly efficacious• Rapidly active• Strong penetrability• Materials compatibility• Non-toxic• Organic material resistance• Adaptability• Monitoring capability• Cost-effectiveSchneider PM. Tappi J. 1994;77:115-119DR.T.V.RAO MD 10
  11. 11. FACTORS THAT INFLUENCE EFFICACY OF DISINFECTION/STERILIZATION  Contact time  Physico-chemical environment (e.g. pH) 3 Presence of organic material 4 Temperature 5 Type of microorganism 6 Number of microorganisms 7 Material compositionDR.T.V.RAO MD 11
  12. 12. burning method(incineration) flowing steam disinfection boiling water disinfection hot air drying method(烤箱) DR.T.V.RAO MD 12
  13. 13. DISINFECTION AND STERILIZATIONEH Spaulding believed that how an object will be disinfected depended on the object’s intended use.CRITICAL - objects which enter normally sterile tissue or the vascular system or through which blood flows should be sterile.SEMICRITICAL - objects that touch mucous membranes or skin that is not intact require a disinfection process (high- level disinfection[HLD]) that kills all microorganisms but high numbers of bacterial spores.NONCRITICAL -objects that touch only intact skin require low-level disinfection.DR.T.V.RAO MD 13
  14. 14. Most Resistant Endospores Mycobacteria Fungal Spores Small Non-enveloped viruses (polio, rotavirus, rabies) Vegetative Fungal Cells Enveloped Viruses (Herpes, Hepatitis B, Hepatitis C, HIV) Vegetative Bacteria Least ResistantDR.T.V.RAO MD 14
  15. 15. SPORICIDAL AGENTS • Glutaraldehyde • Formaldehyde • Other aldehydes • Chlorine-releasing agents • Iodine and iodophores • Peroxygens • Ethylene oxide • P-Propiolactone • A. D. RUSSELL, 1999. Bacterial Spores and Chemical Sporicidal Agents. CLINICAL MICROBIOLOGY REVIEWS Vol. 3, No. 2 p. 99-119 .DR.T.V.RAO MD 15
  16. 16. DR.T.V.RAO MD 16
  17. 17. Physical Methods of Microbial Control:Heat: Kills microorganisms by denaturing theirenzymes and other proteins. Heat resistance varieswidely among microbes.Thermal Death Point (TDP): Lowest temperature at which all of the microbes in a liquid suspension will be killed in ten minutes.Thermal Death Time (TDT): Minimal length of time in which all bacteria will be killed at a given temperature. Decimal Reduction Time (DRT): Time in minutes at which 90% of bacteria at a given temperature will be killed. Used in canning industry. DR.T.V.RAO MD 17
  18. 18. BOILING TEMPERATURE IS LINKED TO PRESSURE• 100 oC at 1 ATM• 121 oC at 2 ATM (1 barr)• 132 oC at 3 ATM (2 barr)• 80 oC at 0.5 ATM (Mont Blanc)• 70 oC at 0.35 ATM (Mont Everest)• 40 oC at 0.02 ATM (Mechanical vacuum)DR.T.V.RAO MD 18
  19. 19. BOILING• Kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses within 10 minutes at sea level• Temperature cannot exceed 100ºC at sea level; steam carries some heat away• Boiling time is critical• Water boils at lower temperatures at higher elevations; requires longer boiling time• Endospores, protozoan cysts, and some viruses can survive boilingDR.T.V.RAO MD 19
  20. 20. PHYSICAL METHODS: HEAT• Pasteurisation • Incineration • the ultimate sterilization • First used with milk: 72°C for 20 seconds • used for disposal of hospital waste • Heating to 80°C for 1 minute will • Wet heat kill most vegetative organisms • Boiling • limited use as spores may be • Examples: bed-pan washer, resistant, boilers may be misused proctoscope • Low temperature steam disinfection• Dry heat (hot air oven) (75°C for 30 mins) • Used for e.g. ventilator tubing • used on waxes, oils (wet heat • Autoclaving usually preferred) • High-temperature steam plus pressure (same principle as pressure cooker) DR.T.V.RAO MD 20
  21. 21. MOIST HEAT• Used to disinfect, sanitize, and sterilize• Kills by denaturing proteins and destroying cytoplasmic membranes• More effective than dry heat; water better conductor of heat than air• Methods of microbial control using moist heat • Boiling • Autoclaving • Pasteurization • Ultrahigh-Temperature SterilizationDR.T.V.RAO MD 21
  22. 22. MOIST HEAT• Pasteurization Definition: a process in which fluids are heated at temperatures below boiling point to kill pathogenic microorganisms in the vegetative state without altering the fluid’s palatability. Conditions: 62℃, 30min or 71.7℃, 15sec Significance: kills vegetative pathogens Applications: milk, beer DR.T.V.RAO MD 22
  23. 23. AUTOCLAVING• Pressure applied to boiling water prevents steam from escaping• Boiling temperature increases as pressure increases• Autoclave conditions – 121ºC, 15 psi, 15 minutesDR.T.V.RAO MD 23
  24. 24. STRUCTURAL DIAGRAM OF AUTOCLAVESDR.T.V.RAO MD 24
  25. 25. STEAM QUALITY IS IMPORTANT  Saturated steam 98% steam, 2% water vapor  Dry steam Superheated  Wet steam SupersaturatedDR.T.V.RAO MD 25
  26. 26. AUTOCLAVEDR.T.V.RAO MD 26 Figure 9.6b
  27. 27. Other Physical Methods of Microbial Control: Filtration: Removal of microbes by passage of a liquid or gas through a screen like material with small pores. Used to sterilize heat sensitive materials like vaccines, enzymes, antibiotics, and some culture media. High Efficiency Particulate Air Filters (HEPA): Used in operating rooms and burn units to remove bacteria from air. Membrane Filters: Uniform pore size. Used in industry and research. Different sizes:  0.22 and 0.45um Pores: Used to filter most bacteria. Don’t retain spirochetes, mycoplasmas and viruses.  0.01 um Pores: Retain all viruses and some large proteins. DR.T.V.RAO MD 27
  28. 28. Physical Methods of Microbial Control:Radiation: Three types of radiation kill microbes:1. Ionizing Radiation: Gamma rays, X rays, electron beams, orhigher energy rays. Have short wavelengths (less than 1nanometer).Dislodge electrons from atoms and form ions.Cause mutations in DNA and produce peroxides.Used to sterilize pharmaceuticals and disposable medicalsupplies. Food industry is interested in using ionizing radiation.Disadvantages: Penetrates human tissues. May cause geneticmutations in humans. DR.T.V.RAO MD 28
  29. 29. FORMS OF RADIATIONDR.T.V.RAO MD 29
  30. 30. Physical Methods of Microbial Control:Radiation: Three types of radiation kill microbes:Microwave Radiation: Wavelength ranges from 1 millimeterto 1 meter.Heat is absorbed by water molecules.May kill vegetative cells in moist foods.Bacterial endospores, which do not contain water, are notdamaged by microwave radiation.Solid foods are unevenly penetrated by microwaves.Trichinosis outbreaks have been associated with pork cookedin microwaves. DR.T.V.RAO MD 30
  31. 31. FILTRATION• Mechanism mechanically removes microorganisms• Application sterilize materials likely to be damaged by heatDR.T.V.RAO MD 31
  32. 32. 滤菌过程 2007-5-26 32DR.T.V.RAO MD 32
  33. 33. HOW COMPLEX A ENDOSCOPE TO STERILIZEDR.T.V.RAO MD 33
  34. 34. DR.T.V.RAO MD 34
  35. 35. CHEMICAL METHODS OF MICROBIAL CONTROL• Major Categories • Phenols • Alcohols • Halogens • Oxidizing agents • Surfactants • Heavy Metals • Aldehydes • Gaseous Agents • AntimicrobicsDR.T.V.RAO MD 35
  36. 36. FACTORS INFLUENCING ANTIMICROBIAL ACTIVITY • the concentration and kind of an agent used • the length of exposure to the agent • the temperature at which the agent is used • the number of microorganisms present • the kinds of microorganisms present • the nature of the material bearing the microorganismDR.T.V.RAO MD 36
  37. 37. PHENOL AND PHENOLICS• Intermediate- to low-level disinfectants• Denature proteins and disrupt cell membranes• Effective in presence of organic matter and remain active for prolonged time• Commonly used in health care settings, labs, and homes (Lysol, triclosan)• Have disagreeable odor and possible side effectsDR.T.V.RAO MD 37
  38. 38. ALCOHOLS• Intermediate-level disinfectants• Denature proteins and disrupt cytoplasmic membranes• Evaporate rapidly – both advantageous and disadvantageous• Swabbing of skin with 70% ethanol prior to injectionDR.T.V.RAO MD 38
  39. 39. ISOPROPYL ALCOHOL (70%)ISOPROPYL ALCOHOL (70%)• Powerful disinfectant and antiseptic• Mode of action: denatures proteins, dissolves lipids and can lead to cell membrane disintegration• Effectively kills bacteria and fungi • But does not inactivate spores!DR.T.V.RAO MD 39
  40. 40. HALOGENS • Intermediate-level antimicrobial chemicals • Believed that they damage enzymes via oxidation or by denaturing them • Iodine tablets, iodophores (Betadine®), chlorine treatment of drinking water, bleach, chloramines in wound dressings, and bromine disinfection of hot tubsDR.T.V.RAO MD 40
  41. 41. OXIDIZING AGENTS• Peroxides, ozone, and per acetic acid kill by oxidation of microbial enzymes• High-level disinfectants and antiseptics• Hydrogen peroxide can disinfect and sterilize surfaces of objects• Ozone treatment of drinking water• Per acetic acid – effective sporocide used to sterilize equipmentDR.T.V.RAO MD 41
  42. 42. SURFACTANTS• Surface active” chemicals that reduce surface tension of solvents to make them more effective at dissolving solutes• Soaps and detergents • Soaps have hydrophilic and hydrophobic ends; good degerming agents but not antimicrobial • Detergents are positively charged organic surfactants• Quats – colorless, tasteless, harmless to humans, and antimicrobial; ideal for many medical and industrial application • Low-level disinfectantsDR.T.V.RAO MD 42
  43. 43. HEAVY METALS• Ions are antimicrobial because they alter the 3-D shape of proteins, inhibiting or eliminating their function• Low-level bacteriostatic and fungistatic agents• 1% silver nitrate to prevent blindness caused by N. gonorrhoeae• Thimerosal (mercury-containing compound) used to preserve vaccines• Copper controls algal growth in reservoirs, fish tanks, swimming pools, and water storage tanks; interferes with chlorophyllDR.T.V.RAO MD 43
  44. 44. ALDEHYDES • Denature proteins and inactivate nucleic acids • Glutaraldehyde both disinfects (short exposure) and sterilizes (long exposure) • Formalin used in embalming and disinfection of rooms and instrumentsDR.T.V.RAO MD 44
  45. 45. PROBLEMS WITH STERILITY• Lack of understanding of risk/process • physicians introducing new products (borrowed, samples) • Multidose vials • What is sterile vs not• Lack of understanding of components of process • MDs, technologists have less training than nurses (anaesthesiology, imaging, urology) DR.T.V.RAO MD 45
  46. 46. GASEOUS AGENTS• Ethylene oxide, propylene oxide, and beta- propiolactone used in closed chambers to sterilize items• Denature proteins and DNA by cross-linking functional groups• Used in hospitals and dental offices• Can be hazardous to people, often highly explosive, extremely poisonous, and are potentially carcinogenicDR.T.V.RAO MD 46
  47. 47. CURRENT STERILIZATION MEANS: PLASMAS?• Yes.• Plasmas are currently employed in many industries to accomplish both highly effective, and delicate sterilization.• Not future technology! Plasmas are used today!• But, how do they work?DR.T.V.RAO MD 47
  48. 48. PLASMA STERILIZATION• A plasma is a quasi-neutral collection of electrons, positive ions, and neutrals capable of collective behavior• Positive ions = free radicals• Plasma sterilization operates synergistically via three mechanisms: • Free radicals interactions • UV/VUV radioactive effects • Volatilization• Dead microorganisms = sterilizationDR.T.V.RAO MD 48
  49. 49. DISADVANTAGES OF PLASMA STERILIZATION• Weak penetrating power of the plasma species. Complications arise in: • Presence of organic residue • Packaging material • Complex geometries • Bulk sterilization of many devices• Solutions: Introduce preferentially targeting UV/VUV radiation of proper wavelength DR.T.V.RAO MD 49
  50. 50. CAN ENVIRONMENTAL CLEANING REDUCE MRSA TRANSMISSION?• Setting: ward with endemic MRSA, and widespread environmental contamination• Before-after study • Cleaning time increased by 57 hours per week • Responsibility for routine cleaning of shared equipment delineated• In 6 months post-intervention, number of MRSA acquisitions decreased fro 30 to 3 per 6 months DR.T.V.RAO MD Rampling A JHI 2001;49:109 50
  51. 51. IMPROVING NON-CRITICAL ITEM/ENVIRONMENT DISINFECTION • Audit and feedback • New technology • Hydrogen peroxide vapour/gas • UV room decontamination? antibacterial surface coatings?Otter ICHE 2009;30(6):574-7 DR.T.V.RAO MD 51
  52. 52. THE PROBLEM OF CJD AND TSES• Creutzfeldt-Jakob syndrome and other transmissible spongiform encephalopathies caused by highly resistant proteinaceous particles, prions• can survive 3 years of environmental exposure and are unusually resistant to conventional decontamination methods• Iatrogenic CJD documented in three circumstances • use of contaminated medical equipment (2 cases) • use of extracted pituitary hormones (> 130 cases) • implantation of contaminated grafts from humans (cornea, 3 cases; dura mater, > 110 cases) DR.T.V.RAO MD 52
  53. 53. INACTIVATION OF PRIONS• Steam sterilization with NaOH• Alkaline cleaner (pH 2.2, 1 hr 23°C)• Copper plus peracetic acid• Vapourized hydrogen peroxide (Sterrad NX)Yan ICHE 2004;25:280, Fichet Lancet 2004;384:251, Baier JHI 2004;57:80,Lemmer J Gen Virol 2004;85:3805; Roger-Kreuz, ICHE 2009;30(8):769-77Lehman Hosp Infect. 2009;72(4):342-50; DR.T.V.RAO MD 53
  54. 54. WHAT IS AN INDICATOR OR STERILISATION CONTROL ? • On paper • Self -contained • Sealed ampulla (spores + broth) • Spores suspension • Tube witness (point of fusion) It is a device conceived to verify if the process operated as expectedDR.T.V.RAO MD 54
  55. 55. VALIDATION OF BIOLOGICAL INDICATORS • The reality : • We do not use the most resistant organisms • The predictive behaviour is generally linear only for one process • Manufacturers seldom use more “practical” strains (read : “less linear” strains for more economical, inoffensive, self resistance and stability) • There is no such thing as a “universal biological indicator” • The choice of any particular strain is therefore a manner of arbitrary choiceDR.T.V.RAO MD 55
  56. 56. 3M RAPID INDICATORDR.T.V.RAO MD 56
  57. 57. QUANTIFYING STERILIZATION EFFICACY•• i.e. Time required for the microbial population to be reduced to one decimal DR.T.V.RAO MD 57
  58. 58. EXCESSIVE USE OF CHEMICALS CAN CREATE RESISTANT MICROBES ??? • Little evidence that extensive use of products containing antiseptic and disinfecting chemicals adds to human or animal health • The use of such products promotes the development ofDR.T.V.RAO MD resistant microbes 58
  59. 59. STERILIZATION IS SUCCESSFUL WITH PERSONNEL: HYGIENE• Avoid cleanrooms when ill• Frequent bathing and shampooing• Avoid cosmetics such as face powder, hair sprays, perfumes and aftershave• Clothing should be clean, nonfrayed and nonlinting• Avoid smokingDR.T.V.RAO MD 59
  60. 60. WHO / WHAT IS IMPORTANT IN PREVENTION OF INFECTIONS
  61. 61. WE ARE ALL IMPORTANT
  62. 62. • Programme created by Dr.T.V.Rao MD for Medical and Paramedical Professionals in the Developing World • Email • doctortvrao@gmail.comDR.T.V.RAO MD 62

×