Sanitation, Disinfection and Sterilization

1. Sanitation, Disinfection and Sterilization

2. Learning Outcomes After this section is completed you should be able to: List the classes of pathogenic organisms in order of their resistance to destruction Differentiate between sanitation, disinfection and sterilization List the different ways that microbial control methods destroy or inhibit pathogenic organisms

3. Learning Outcomes After this section is completed you should be able to: List the five categories of physical methods of microbial control Name and describe the physical methods of microbial control Identify the level of microbial control achieved with each of the physical methods State an example of the application of each of the physical methods of microbial control

4. Learning Outcomes After this section is completed you should be able to: List the properties of the �ideal chemical agent� for microbial control Name and describe the classes of microbial control chemicals Identify the level of microbial control achieved by the chemical classes

5. Learning Outcomes After this section is completed you should be able to: List the advantages and disadvantages of the autoclave in animal care facilities Explain the function of the autoclave Compare and contrast the different autoclaves

6. Learning Outcomes After this section is completed you should be able to: Describe the preparation of each of the following for processing in the autoclave: linen packs, pouch packs, hard goods, liquids and contaminated objects List the guidelines for loading the autoclave chamber Compare the three different autoclave cycles

7. Learning Outcomes After this section is completed you should be able to: List and define the five methods of quality control for sterilization List and define the two methods of quality control for disinfection

8. Section Outline Levels of microbial resistance Degrees of microbial control How microbial control methods work Methods of microbial control Autoclave Quality control for sterilization and disinfection

9. Overarching Principle The objective in sanitation, sterilization and disinfection is to control microorganisms, or pathogens, in the environment, thus protecting patients and staff from contamination and disease, and thereby promoting optimal healing and wellness.

10. The Ever Present Danger Improper application of the methods of sanitation, sterilization and disinfection can lead to microbial resistance and increase the risk of nosocomial infection

11. Levels of Microbial Resistance Pathogens Microorganisms that cause disease Viruses Bacteria Fungi Protozoan Prions Different classes of pathogens vary in their resistance to destruction by chemical methods

13. Levels of Microbial Resistance Microbial control Is achieved by using methods of sanitation, disinfection and sterilization Microbial control Done to a degree that is practical, efficient and cost effective

14. Levels of Microbial Resistance Sterility is used only when necessary In many situations sanitation and disinfection create acceptable levels of microbial control

15. Degrees of Microbial Control Sterilization is the elimination of all life from an object Complete microbial control Asepsis is a condition in which no living organisms are present Free of infection or infectious material

16. Degrees of Microbial Control Sanitation: The state of being clean and conducive to health. Disinfection: To cleanse so as to destroy or prevent the growth of disease-carrying microorganisms

17. Degrees of Microbial Control Disinfection, sanitation and cleaning remove most microorganisms Most disinfectants are microbiocidal Microbes are killed Some disinfectants are bacteriostatic Microbial growth is inhibited

18. Degrees of Microbial Control Disinfectants can be classified according to their spectrum of activity Bacteriocidal Bacteriostatic Sporocidal Virucidal Fungicidal

19. How Microbial Control Methods Work Mode of Action Different physical and chemical methods destroy or inhibit microbes in several ways Damage cell walls or membranes Interfere with cell enzyme activity or metabolism Destroy microbial cell contents through oxidation, hydrolysis, reduction, coagulation, protein denaturation or the formation of salts

20. Efficacy of Microbial Control The effectiveness of all microbial control methods depends on the following factors: Time Most methods have minimum effective exposure times Temperature Most methods are more effective as temperature increases

21. Efficacy of Microbial Control The effectiveness of all microbial control methods depends on the following factors: Concentration and Preparation Chemical methods require appropriate concentrations of agent Disinfectants may be adversely affected by mixing with other chemicals Organisms Type, number and stage of growth of target organisms

22. Efficacy of Microbial Control The effectiveness of all microbial control methods depends on the following factors: Surface Physical and chemical properties of the surface to be treated may interfere with the method�s activity Some surfaces are damaged by some methods

23. Efficacy of Microbial Control The effectiveness of all microbial control methods depends on the following factors: Organic debris or other soils Will dilute, render ineffective or interfere with many control methods Method of application Items may be sprayed, swabbed or immersed in disinfectants Cotton and some synthetic materials may reduce chemical activity

24. Methods of Microbial Control Physical Methods Chemical Methods

25. Physical Methods Dry Heat Oxidation Moist Heat Denatures microbial protein Radiation Damages cell enzyme systems and DNA Filtration Traps organisms that are too large to pass through the filter Ultrasonic Vibration Coagulates proteins and damages cell walls

26. Dry Heat Incineration Material or object is exposed to a hot fire Object must become red hot as in the inoculation loops used in microbiology Used to dispose of tissue or carcasses Efficacy: complete sterilization

27. Dry Heat Hot Air Oven Sterility requires 1 hour of exposure @ 170� C(340� F) Powders and non-aqueous liquids like paraffin or Vaseline Used in some animal care facilities and useful in domestic applications (e.g. the kitchen oven) Efficacy: complete sterilization

28. Dry Heat Drying Most organisms require humidity to survive and grow More commonly used to prevent spoiling and preserve foodstuffs (e.g. raisins) Efficacy: incomplete sterilization

29. Moist Heat Hot Water Used to clean and sanitize surfaces Addition of detergents increases efficacy by emulsifying oils and suspending soils so they are rinsed away Efficacy: incomplete sterilization

30. Moist Heat Boiling Requires 3 hours of boiling to achieve complete sterilization Boiling for 10 minutes will destroy vegetative bacteria and viruses but not spores Addition of 2% calcium carbonate or sodium carbonate will inhibit rust and increase efficacy Useful for field work Efficacy: may be complete sterilization

31. Moist Heat Steam Similar to boiling because the temperature is the same Exposure to steam for 90 minutes kills vegetative bacteria but not spores Efficacy: incomplete sterilization

32. Moist Heat Steam under pressure Pressure increases the boiling point such that the temperature of the water becomes much higher that 100� C (212� F) The autoclave utilizes steam under pressure to achieve sterilization This is the most efficient and inexpensive method of sterilization for routine use Efficacy: complete sterilization

33. Radiation Ultraviolet (UV) Low energy UV radiation is a sterilant when items are placed at a close range UV radiation has no penetrating ability Used to sterilize rooms Very irritating to eyes Efficacy: may be complete sterilization

34. Radiation Gamma radiation Ionizing radiation produced from a Cobalt 60 source Good penetrating ability in solids and liquids Used extensively in commercial preparation of pharmaceuticals, biological products and disposable plastics Efficacy: complete sterilization

35. Filtration Fluid filtration Forced through a filter with either positive or negative pressure Filter is most commonly a synthetic screen filter with micropore openings Used to sterilize culture media, buffers and pharmaceuticals Pore size of 0.45�m removes most bacteria Microplasmas and viruses require 0.01�m to 0.1�m May be used in conjunction with a pre-filter Efficacy: can be complete sterilization

36. Filtration Air filtration Examples of usage: surgical masks, laboratory animal cages and air duct filters Fibrous filters made of various paper products are effective for removing particles from air Efficacy is influenced by air velocity, relative humidity and electrostatic charge Efficacy: can be complete sterilization

37. Filtration Air filtration HEPA: high efficiency particle absorption filters are 99.97% to 99.997% effective in removing particles with diameters greater that 0.3�m

38. Filtration Air filtration Surgical masks Designed to protect the patient from the surgeon, not the surgeon from the patient Special masks are available that are designed to protect personnel from animal pathogens Masks must fit snugly, stay dry and be changed every 3 to 4 hours to remain effective

39. Ultrasonic Vibration Cavitation High frequency sound waves passed through a solution create thousands of cavitation �bubbles� Bubbles contain a vacuum; as they implode or collapse, debris is physically removed from objects Effective as an instrument cleaner Efficacy: incomplete sterility

40. Chemical Methods Many chemicals are available to sterilize, disinfect or sanitize None is the �ideal� agent Chemicals penetrate cell walls and react with cell components in various ways to destroy or inhibit growth Many chemicals are disinfectants with varying levels of efficacy Some are sterilants

41. Chemical Methods Bacteria Viruses Level Vegetative Acid-fast Spores Lipophilic Hydrophilic High + + + + + Medium + + 0 + +/- Low + 0 0 +/- 0 Examples: High: Aldehydes, VPHP, Chlorine-dioxide Medium: Alcohols, Phenols, 7th generation Quats Low: Quats

43. Chemical Methods Ideal chemical agent Broad spectrum of activity Does not stain or damage surfaces Stable after application Effective in a short time Nonirritating and nontoxic to surfaces and tissues Inexpensive and easy to store and use Not affected by organic debris or other soil Effective at any temperature Nontoxic, nonpyrogenic and nonantigenic Possesses residual and cumulative action

44. Chemical Methods Soaps Detergents Quaternary ammonium compounds Phenols Aldehydes Halogens Chlorine and chlorine releasing compounds Alcohols Peroxygen compounds Ethylene Oxide

45. Chemical Methods Soaps Anionic cleaning agent made from natural oils Ineffective in hard water Does not mix well with quats and decreases the effectiveness of halogens Is not antimicrobial Minimal disinfectant activity

46. Chemical Methods Detergents Synthetic soaps Anionic, cationic or nonionic; anionic combined with cationic will lead to neutralization of both Most are basic; a few are acidic Emulsify grease and suspend particles in solution May contain wetting agents

47. Chemical Methods Quaternary Ammonium Compounds Quats: Centrimide, benzalkonium chloride, Zephiran, Quatsyl-D, Germiphene Effective against gm+ and gm- microorganisms and enveloped viruses Low toxicity and generally nonirritating Prolonged contact irritates epithelial tissues

48. Chemical Methods Quaternary Ammonium Compounds Inactivated by organic material, soap, hard water and cellulose fibers Reduced efficacy in presence of organic debris, soap, detergents and hard water Ineffective sporocide and fungicide Bacteria not destroyed may clump together; those inside the clump are protected Dissolves lipids in cell walls and cell membranes

49. Chemical Methods Quaternary Ammonium Compounds Organically substituted ammonium compounds More effective in basic pH Cationic detergent Deodorizes

50. Chemical Methods Phenols Active against gm+ bacteria and enveloped viruses Developed from phenol or carbolic acid Synthetic phenols are prepared in soap solutions that are nontoxic and nonirritating Prolonged contact may lead to skin lesions

51. Chemical Methods Phenols Toxic to cats because cats lack the inherent enzymes needed to detoxify the compound May be toxic to rodents and rabbits Not inactivated by organic matter, soap or hard water Activity decreased by quats

52. Chemical Methods Aldehydes Active against gm+ and gm-, most acid fast bacteria, bacterial spores, most viruses and fungi Considered to be a sterilant but may require prolonged contact

53. Chemical Methods Aldehydes Gluteraldehyde (Cidex) Noncorrosive Supplied as an acid, activated by adding sodium bicarbonate Good for plastics, rubber, lenses in �cold sterilization� Not inactivated by organic material or hard water Irritating to respiratory tract and skin

54. Chemical Methods Aldehydes Formaldehyde (Formicide) Aqueous solution 37% to 40% (w/v) formaldehyde May be diluted with water or alcohol Irritating to tissues and respiratory tract A vapor phase surface disinfectant that slowly yields formaldehyde

55. Chemical Methods Aldehydes Biguanide (e.g. chlorhexidine gluconate [Hibitane, Precyde]) Active against gm+, most gm-, some lipophilic viruses and fungi Efficient disinfectant, used mostly as an antiseptic Some reduction of activity in presence of hard water and organic material Immediate, cumulative and residual activity Precipitates to an inactive form when mixed with a saline solution Used as a surgical scrub and hand wash Low toxicity

56. Chemical Methods Halogens Chlorine, iodine, fluorine and bromine Active against gm+ and gm-, acid fast, all viruses and fungi Iodine most common Chlorine and chlorine releasing compounds

57. Chemical Methods Halogens Iodine Used in solution with water or alcohol Iodophors: iodine plus carrier molecule that acts to release iodine over time Surgical scrub (Betadine): iodophor plus detergent Tinctures and solutions: iodines and iodophors w/o detergent Nonstaining and nonirritating Inactivated by organic material Aqueous forms are staining, irritating and corrosive to metals, especially if used undiluted

58. Chemical Methods Halogens Chlorine and chlorine releasing compounds (e.g. chlorine gas, chlorine dioxide) Commonly available as sodium hypochlorite Least expensive and most effective chemical disinfectant Available chlorine equals oxidizing ability Damages fabrics, corrosive to metals Inactivated by organic debris May require several minutes of contact to be effective Skin and mucous membrane irritant if not diluted properly or rinsed well

59. Chemical Methods Alcohols Ethyl alcohol, isopropyl alcohol, methyl alcohol Active against gm+ and gm- bacteria and enveloped viruses Most effective when diluted to 60% to 70% (isopropyl), 705 to 80% (ethyl)

60. Chemical Methods Alcohols Used as a solvent for other disinfectants and antiseptics Most commonly used skin antiseptic Low cost and low toxicity

61. Chemical Methods Alcohols Irritating to tissues and painful on open wounds Repeated use dries skin Forms coagulum in presence of tissue fluid Consists of a layer of tissue fluid whose proteins have been denatured by alcohol Facilitates survival of bacteria under the coagulum Fogs lenses, hardens plastics and dissolves some cements

62. Chemical Methods Alcohols Inactivated by organic debris Ineffective after evaporation Defatting agent

63. Chemical Methods Peroxygen compounds (e.g. Peracetic acid) Active against gm+ and gm-, acid-fast, fungi. No virucidal activity Classified as a sterilant but may not kill pinworm eggs

64. Chemical Methods Peroxygen compounds (e.g. Peracetic acid) Oxidizing agent Reacts with cellular debris to release oxygen Kills anaerobes Applied as a 2% solution for 30 minutes at 80% humidity Explosive and can damage iron, steel and rubber Irritating to healthy tissues

65. Chemical Methods Ethylene Oxide Active against gm+ and gm-, lipophilic and hydrophilic viruses, fungi and bacterial spores Classified as a sterilant Effective sterilant for heat labile objects

66. Chemical Methods Ethylene Oxide EO is a colorless nearly odorless gas that diffuses and penetrates rapidly Flammable and explosive Toxic, carcinogenic and irritating to tissue

67. Chemical Methods Ethylene Oxide Used in a chamber with a vacuum May be mixed with CO2, ether or freon Used at temperatures of 21� to 60� C (70� to 140� F) Works quicker at higher temperatures Exposure times of 1 to 18 hours Requires minimum relative humidity of 30% (40% is optimum Items must be clean and dry and can be wrapped muslin, polyethylene, polypropylene or polyvinyl Sterilized items must be ventilated in a designated area for 24 to 48 hours to dissipate residual EO

68. Autoclave Advantages Consistently achieves complete sterility Inexpensive and easy to operate Safe for most surgical instruments and equipment, drapes and gowns, suture materials, sponges and some plastics and rubbers Safe for patients and personnel Established protocols and quality control indicators are easy to access

69. Autoclave Disadvantages Staff may overestimate the ability of the autoclave Sterility depends on saturated steam of the appropriate temperature having contact with all objects within the unit for a sufficient length of time Requires a thorough understanding of techniques to ensure that the above occurs

70. Autoclave Function Heat is the killing agent Steam is the vector that supplies the heat and promotes penetration of the heat Pressure is the means to create adequately heated steam

71. Autoclave Function Complete sterilization of most items is achieved after 9 to 15 minutes exposure to 121� C (250� F) Steam at sea level is 100� C (212� F) as pressure is increased the temperature of the steam increases The minimum effective pressure of the autoclave is 15 pounds per square inch which provides steam at 121� C (250� F) Many autoclaves attain 35 psi which creates steam temperature of 135� C (275� F)

72. Autoclave Function Exposure times must allow penetration and exposure of all surfaces to 121�C (250� F) steam Exposure time is decreased by increasing pressure, which increases steam temperature

73. Steam Sterilization Temperature/ Pressure Chart Temperature Pressure(psi) �C �F Time(mins) 0 100 212 360 15 121 250 9-15 20 125 257 6.5 25 130 266 2.5 35 133 272 1

74. Autoclave Types Gravity displacement autoclave Prevacuum autoclave

75. Autoclave Types Gravity displacement Water is heated in a chamber Continued heating creates pressure Steam displaces air within the chamber forcing it out through a vent Cycle timing begins when the temperature reaches at least 121�C

76. Autoclave Types Gravity displacement After sufficient exposure time, steam is exhausted through a vent back into a reservoir Air that has been sterilized within the jacket and then filtered is admitted back into the chamber to replace the exhausting steam If the chamber is loaded improperly or there is insufficient steam, there will be air pockets remaining in the chamber that will interfere with steam penetration and result in non-sterile areas The load must be dried within the autoclave

77. Autoclave Types Prevacuum Usually a much larger and more costly machine Equipped with a boiler to generate steam and a vacuum system Air is taken out of the loaded chamber by means of the vacuum system Steam at 121�C or more is introduced into the chamber The steam immediately fills the chamber to eliminate the vacuum Exposure time begins immediately At completion of the cycle steam is vacuumed and replaced by hot, dry sterile air Air pockets are eliminated and processing times are reduced due to the vacuum

78. Autoclave Operation Preparation of the load Loading the chamber Autoclave cycles

79. Autoclave Operation Preparation of the load Linen packs Pouch packs Hard goods Liquids Contaminated objects

80. Autoclave Linen packs All instruments in packs are scrupulously cleaned and rinsed in de-ionized water Instruments are disassembled and ratchets are left closed and unlocked Appropriate lines are in good repair and freshly laundered Disposable linens are not reused

81. Autoclave Linen packs A chemical sterilization indicator is included in every pack Chemical sterilization indicators provide verification that the inside of the pack was exposed to appropriate sterilization temperatures for the appropriate length of time

82. Autoclave Linen packs The pack is wrapped using at least two layers of material The shelf life of the sterilized pack varies with the type of the outer wrapping Pack is sealed with autoclave tape and labeled with the date, contents and operator Autoclave tape provides verification that the outside of the pack was exposed to appropriate sterilization temperatures

83. Autoclave SHELF LIFE Wrapper Shelf-life Dbl wrapped two layer muslin 4 wk Dbl wrapped two layer muslin 6 mo heat sealed in dust covers after sterilization Dbl wrapped two layer muslin 2 mo tape sealed in dust covers after sterilization Dbl wrapped non-woven barrier 6 mo materials (paper) Paper/plastic peel pouches, heat sealed 1 year Plastic-peel pouches, heat sealed 1 year

84. Autoclave Linen packs Pack should not exceed 30 X 30 X 50 cm (12 X 12 X 20 inches) in size Pack should not exceed 5.5 kg (12 lb) in weight Pack should not exceed 115 kg/m3 in density

85. Autoclave Pouch packs Used for single instruments, sponges, etc. Previous guidelines apply Pouches are heat sealed or ends are rolled and securely taped with autoclave tape Labeled as above

86. Autoclave Hard goods Stainless steel or other hard instruments, trays, bowls, laboratory cages and other equipment may be autoclaved without wrapping Must be physically clean and rinsed in de-ionized water Syringes and plungers are separated before autoclaving

87. Autoclave Liquids Contained in Pyrex flasks 3 times larger than contents require Cover loosely with applied lid or paraffin film, or place a needle through the stopper to allow air exchange Sterility of liquids processed in the autoclave is in question Removing liquids from the chamber is hazardous to personnel

88. Autoclave Contaminated objects Used before disposal to decontaminate syringes, culture plates, etc., that contain biohazardous waste Place objects in a container appropriate for disposal Special autoclavable biohazard bags are available

89. Autoclave Chamber loading Must allow free circulation of steam Use perforated or wire mesh shelves Linen packs have 2.5cm to 7.5cm space between Place multiple packs on edge instead of stacking Paper/plastic pouches are placed in specially designed baskets that support them on edge with the paper side of each package facing the plastic side of the adjacent package Solid bowls or basins are placed upside down or on edge Mixed loads (hard goods and wrapped goods) have wrapped goods on upper shelf

90. Autoclave Autoclave cycles Wrapped goods Hard goods Liquids

91. Autoclave Autoclave cycles Wrapped goods Has �dry� cycle that allows wrapped packs to dry Used for most surgical packs

92. Autoclave Autoclave cycles Hard goods Has no dry cycle Used for trays, bowls, cages, etc. that will not be maintained in a sterile condition Also used for flash autoclaving to quickly sterilize instruments that are needed immediately

93. Autoclave Autoclave cycles Liquids Exhausts steam more slowly than other cycles Used for liquids that would be forced from containers during a faster exhaust cycle

94. Quality Control The effectiveness of any method of microbial control must be monitored regularly Verification of the effectiveness of microbial control should be performed at least monthly

95. Quality Control Methods Recording thermometer Thermocouple Chemical indicator Biological testing Bowie Dick test Surface sampling Serology

96. Quality Control Methods Recording thermometer Displays the temperature of the autoclave chamber Operator observes for correct temperature during cycle Some autoclaves are equipped with printed tape of chamber temperatures during cycle

97. Quality Control Methods Thermocouple Used in steam and dry heat sterilization chambers Temperature sensors are placed in the part of a test pack that is most inaccessible to steam penetration

98. Quality Control Methods Chemical indicator Paper strips impregnated with sensitive chemicals change color when conditions of sterility are met Used with autoclaves and ethylene oxide systems Placed deep inside packs before sterilization

99. Quality Control Methods Biological testing Bacterial spores are exposed to autoclave or ethylene oxide and then cultured Recommended method for verification of proper autoclave operation in veterinary clinics

100. Quality Control Methods Bowie Dick test Tests pre-vacuumed autoclaves for complete removal of air and uniform steam penetration Uses a pack of uniform dimensions with a cross of autoclave tape in the center

101. Quality Control Methods Surface sampling Surface to be tested is swabbed with a sterile applicator and transferred to a suitable media plate for growth Surface or item is rinsed with a sterile solution, which is examined for contamination �Contact plate� of media is touched to the surface and incubated Recommended method for ensuring proper disinfection of surgical suites in veterinary clinics

102. Quality Control Methods Serology The presence of viruses in the environment is monitored by serological testing of animals to determine the presence of antibodies Animals maintained for this purpose are referred to as sentinel animals