Sterilization, Disinfection and Antisepsis
For the control of infections Prevention Principles of Sterilization, Disinfection and Antisepsis Treatment Chemotherapy
Definitions Sterilization Disinfection Antisepsis Germicide Sporocide
Germicide: Chemical agent capable of killing microbes, spores may survive Sporicide: Germicide capable of killing spores
Cidal_agents that kill Bactericidal Fungicidal Static_inhibit growth Bacteriostatic Fungistatic Bacteriolytic
Sterilization Total destruction of all microbes, including Prions(the most resistant) Bacterial spores Mycobacteria Nonenveloped (nonlipid) viruses Fungi Enveloped viruses are the most sensitive
Sterilization Physical methods Chemical methods
Sterilization Physical methods: Heat Filtration Radiation
Sterilization by heat The most common method Except heat sensitive materials and Toxic or volatile chemicals
Sterilization by heat Moist heat Dry Heat
Dry heat 171º C 1 h 160 ºC 2h Special chambers (Pasteur s oven) The effectiveness is monitored by Bacillus subtilis (which is relatively resistant to killing by dry air)
Moist heat Boiling: relatively low temperature (100 ºC) Vegetative but not spores are killed
Moist heat Autoclave: 121º C da 15 min under steam pressure Air pockets should be avoided It prevents the penetration of steam
Autoclave control Bacillus stearothermophilus Placed in the center of the load Incubated at 37ºC If the sterilization is successful The organism fail to germinate
Tyndalization 100º C for 30 min 3 days Was an alternative to autoclave
Pasteurization Kills pathogenic bacteria Mycobacterium tuberculosis Brucella abortus Salmonella Streptococcus in milk 63º C 30 min 72 ºC 15 seconds(flash pasteurization)
Pasteurization Kills pathogenic bacteria Spores are not affected Should be kept in the fridge
Filtration Removes bacteria and fungi High-efficiency particulate air (HEPA) From air and solutions They can not remove viruses and smaller bacteria
Filtration 0.22-0.45 mikrometer pore size Viruses and mycoplasma pass
Radiation Ultraviolet (limitation: direct exposure) Ionizing radiation (microwave or gamma rays)
Ultraviolet radiation Not penetrates Damages DNA by forming pyrimidine dimers Laboratories,hospital rooms, operating rooms Biological safety cabinets For air and surface sterilization For water sterilization
Ultraviolet radiation 254 nm
Ionizing radiation Microwave Gamma radiation
Ionizing radiation Sterilization of pharmaceuticals Disposable medical supplies Such as plastic syringes and surgical gloves In food industry in increasing shelf lifes Gamma rays from Cobalt 60 High penetration
Sterilization Chemical methods: Gas:commonly used Ethylene oxide (Strict regulations: extremely toxic) Formaldehyde gas (carcinogenic:hepa filters) Hydrogen peroxide vapors plasma gas sterilization:less toxic Chlorine dioxide gas: less toxic
Etylene oxide (EtO) Penetrates paper,cloth, plastics Disposable petri dishes, syringes,cathetersand sutures Food industry İnstruments Toxic and explosive
Sterilization Liquid chemical sterilants Peracetic acid 0.2% Excellent activity Non-toxic end products Glutaraldehyde 2% Toxic
Disinfection Destroying most of the microbial forms Bacterial spores and relatively resistant organisms remain viable, High-,intermediate-,low -level agents
High-level disinfectants Items involved with invasive procedures Which can not withstand sterilization Endoscopes Surgical instruments
High-level disinfectants Preceeded by cleaning the surface To remove organic matter Moist heat (75-100 C for 30 min) Glutaraldehyde (2%) Hydrogen peroxide (3%-25%) Peracetic acid (variable) Chlorine dioxide (100 to 1000ppm free chlorine)
Intermediate- disinfectants Surfaces or instruments in which contamination with highly resistant organisms is unlikely Alcohol (ethly, isopropyl)70-95% Iodophor compounds 30-50ppm /L Phenolic compounds 0.4%-5%
Intermediate- disinfectants Semicritical instruments: Flexible fibreoptic endoscopes Laryngoscopes Vaginal specula Anesthesia breathing circuits
Low-level- disinfectants Quarternary ammonium compounds ( 0.4-1.6%) Blood pressure cuffs Electrocardiogram electrodes Stethoscopes
Level of disinfectants Blood contamination: high-level disinfection Dirty surfaces such as floors and sinks.
Antisepsis Use of chemical agents on skin or other living tissue To eliminate microorganisms No sporicidal action is implied. They reduce the number of microbes on skin surfaces
Antiseptic agents Alcohol 70-90% Iodophor Chlorhexidine 0.5-4% 1-2mg free iodine/l ; 1-2 % iodine Parachlorometaxylenol 0.5-3.75% Triclosan 0.3-2%
Alcohols Excellent activity against all groups of organisms Except spores Non-toxic Inactivated by organic material
Iodophors Excellent activity (skin antiseptics) Slightly more toxic Inactivated by organic material Frequently used with alcohols
Chlorhexidine Broad antimicrobial activity Slow but persistant activity Organic material and high ph decrease its effectiveness.
Parachlorometaxylenol Activity limited to gram-positive bacteria Nontoxic with residuel activity Used in handwashing
Triclosan Active against bacteria But not against other microorganisms Common antiseptic agent in soaps and some toothpastes
Ethylene Oxide Colorless gas Soluble in water Used in sterilization of heat sensitive items
Ethylene Oxide Sterilization Slow İnfluenced by concentration of gas Relative humudity Moisture content Exposure time Temperature
Ethylene Oxide Sterilization Doubling the concentration reduces the exposure time 50% Each 10º C increase doubles the activity Optimal humidity 30%
Ethylene Oxide Sterilization A strong alkylating gas Can damage viable tissue Aeration period 24h Effectiveness monitored by B. Subtilis
Strong alkylating gases Formaldehyde Beta-propiolactone
Aldehydes Affect by alkylation Formaldehyde Glutaraldehyde Sterilant and high-level disinfectant
Aldehydes Formaldehyde gas dissolved in water 37%= Formalin Microbicidal effect enhanced by addition of alcohol 20% formalin+70% alcohol Toxic to skin and mucous membranes
Glutaraldehyde Less toxic Still causes burns Activated by sodium hydoxide (alkaline ph) İnactivated by organic material
Oxydizing agents Ozone, peracetic acid Hydrogen peroxide 3%-6%: most bacteria are killed 10%-25%: all Used to disinfect plastic implants, contact lenses and surgical prostheses
Halogens Iodine and chlorine Iodine compounds: Presipitates proteins and oxidizes essential enzymes Microbicidal against all organisms including spore-forming bacteria and mycobacteria Affected by organic material Povidone iodine: nontoxic
Halogens Chlorine Organic material and alkaline detergents reduce its activity Good germicidal activity Spore-forming bacteria 10-1000 fold more resistant than vegetative
Chlorine With water forms hypochlorous acid A powerful oxidizing agent 0.5-1.0 part per million (ppm)
Phenolic compounds Are rarely used now Historical interest A comparative standart for assesing the germicidal activity of other compounds Phenol coeficient 1 indicates equivalent activity Heaxchlorophene
Quaternary Ammonium compounds Benzalkonium chloride Cetylpyridinium chloride Denaturate cell membrane to release intracellular components
Quaternary Ammonium compounds Bacteriostatic at low Bacteriosidal at high concentrations Pseodomonas, Mycobacterium, many viruses, some fungi, spores are resistant
Alcohols Ethanol İsopropanol Active against vegetative bacteria, Mycobacteria, some fungi, lipid-containing viruses Activity is higher in the presence of water (70%)
Alcohols No activity against spores Poor activity against some fungi and nonlipid containing viruses Common skin antiseptic following iodophor