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Factors Affecting The Sterilization Efficacy

Dr. Alaa gad MD,CICGDIPC,MOHCBAHI SURVYOR 1DISINFECTIONThe process of freeing an article or a surface from all or some of the living microorganisms but not necessarily bacterial spores

4/14/20142SterilizationThe process of freeing an article or a surface from all living microorganisms including viruses & bacterial spores

4/14/20143The activity of germicides against microorganisms depends on a number of factors, some of which are intrinsic qualities of the organism, others of which are the chemical and external physical environment.

4/14/20144Factors affecting DISINFECTIONConc of disinfectantTime of actionpH of the mediumTemperatureNature & number of organismsPresence of extraneous materialOthers hardness of water, relative humidity4/14/20145Number of Microorganisms

The larger the number of microbes, the more time a germicide needs to destroy all of them. Spaulding illustrated this relation when he employed identical test conditions and demonstrated that it took 30 minutes to kill 10B. atrophaeus(formerlyBacillus subtilis) spores but 3 hours to kill 100,000Bacillus atrophaeusspores.Reducing the number of microorganisms that must be inactivated through meticulous cleaning, increases the margin of safety when the germicide is used according to the labeling and shortens the exposure time required to kill the entire microbial load.

4/14/20146Location of MicroorganismsMedical instruments with multiple pieces must be disassembled and equipment such as endoscopes that have crevices, joints, and channels are more difficult to disinfect because penetration of the disinfectant of all parts of the equipment is difficult.Must be no air pockets and the equipment must be completely immersed for the entire exposure period.

4/14/20147Concentration and Potency of Disinfectants

With other variables constant, and with one exception (iodophors), the more concentrated the disinfectant, the greater its efficacy and the shorter the time necessary to achieve microbial kill.

4/14/20148Temperature / PH The activity of most disinfectants increases as the temperature increases, too great an increase in temperature causes the disinfectant to degrade and weakens its germicidal activity and produce a potential health hazard.An increase in pH improves the antimicrobial activity of some disinfectants (e.g., glutaraldehyde, quaternary ammonium compounds) but decreases the antimicrobial activity of others (e.g., phenols, hypochlorites, and iodine). The pH influences the antimicrobial activity by altering the disinfectant molecule or the cell surface.4/14/20149Humidity / water hardness Relative humidity is the single most important factor influencing the activity of gaseous disinfectants/sterilants.Water hardness reduces the rate of kill of certain disinfectants because divalent cations (e.g., magnesium, calcium) in the hard water interact with the disinfectant to form insoluble precipitates.

4/14/201410Factors Affecting The Sterilization Efficacy

4/14/2014111. CleaningFailure to adequately clean instrument results in higher bioburden, protein load, and salt concentration. These will decrease sterilization efficacy.

4/14/2014122. BioburdenThe natural bioburden of used surgical devices is 100 to 103 organisms(primarily vegetative bacteria), which is substantially below the 105-106 spores used with biological indicators.

4/14/2014133.Pathogen typeSpore-forming organisms are most resistant to sterilization and are the test organisms required for FDA clearance. However, the contaminating microflora on used surgical instruments consists mainly of vegetative bacteria.

4/14/2014144. ProteinResidual protein decreases efficacy of sterilization. However, cleaning appears to rapidly remove protein load.

4/14/2014155.SaltResidual salt decreases efficacy of sterilization more than does protein load. However, cleaning appears to rapidly remove salt load.

4/14/2014166. Biofilm accumulationBiofilms are microbial communities that are tightly attached to surfaces and cannot be easily removed. Bacteria within biofilms are up to 1,000 times more resistant to antimicrobials than are the same bacteria in suspension. Chlorine and monochloramines can effectively inactivate biofilm bacteria. Biofilms have been found in whirlpools, dental unit waterlines, and numerous medical devices (e.g., contact lenses, pacemakers, hemodialysis systems, urinary catheters, central venous catheters, endoscopes)Some enzymesand detergentscan degrade biofilms or reduce numbers of viable bacteria within a biofilm, but no products are EPA-registered or FDA-cleared for this purpose.4/14/2014177. Lumen lengthIncreasing lumen length impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.

4/14/2014188. Lumen diameterDecreasing lumen diameter impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.

4/14/2014199. Restricted flowSterilant must come into contact with microorganisms. Device designs that prevent or inhibit this contact (e.g., sharp bends, blind lumens) will decrease sterilization efficacy.

4/14/20142010. Device design and constructionMaterials used in construction may affect compatibility with different sterilization processes and affect sterilization efficacy. Design issues (e.g., screws, hinges) will also affect sterilization efficacy.

4/14/2014214/14/201422Thank you