Sterilization

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Sterilization , sterilization methods including quality contro

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Sterilization methods (including quality control) By D. Rawan :

Sterilization methods (including quality control) By D. Rawan

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Sterilization is killing or removal of all micro organism, including bacteria spores ,which are highly resistance . What do we mean by sterilization?

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Sterilization methods First method heat We can use either dry heat or moist heat Most of micro organisms die at the temperature about 60 c although some are thermophilic Problems comes from spore forming bacteria . Some spore can live in boiling water for an hour or two . So boiling is not enough for spores . E.g. clostridium tetani that cause tetanus . So we need a temperature above 100 c to do proper sterilization.

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Examples of sterilization by dry heat 1- the hot air oven found in the operation room it use a temperature of 170 c and the item remain for on hour . 2- burning using a spirit or alcohol . This is done when no way for sterilization. 3- incineration for removal of waste product and disposable materials. Any hospital should have incineration to get rid of microorganisms. 4- flaming sterilization of the loop used in culturing to get a pure culture.

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The mechanism used in sterilization by moist heat is auto – clave on of the best ways of sterilization it have many types ranging from the simple portable to the full automatic autoclave. The principle of the auto clave is stem under pressure So the temperature rises above 100c whenever you increase the pressure the temperature increase (in higher altitudes the water boil at less than 100 c ) the temperature used generally at the autoclave is 121c gated by pressure of 15 pounds . Then when it reaches 121c we leave the item for 15 minutes (unlike the hot air oven there is no steam so temperature don't follow pressure)

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Second method filtration The concept is to have a filter with pores smaller than size of the microorganisms. The problem here is that the size of microorganisms like bacteria is so small so that the pores difficult to be done. The flask should be sterile . Fluid come down by pressure , we press the mixture . But always by pressure we fear the filter to be ruptured. The importance of filtration is that some certain fluid needed can be affected by heat e.g. the serum if we want to sterilized It to get antitoxins and antibodies from it . Types of filters : 1- cellulose membrane filter . 2- seize filter . 3- sintered filter.

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Third method radiation For something we can't heat it and we can't filter it. E.g. all plastic instruments like syringes they are sterilized by radiation . Radiation affects the DNA of the microorganisms . Example of radiation is a radiation that kill the microorganisms.

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Fourth method chemicals Chemicals agents acts primarily by one of these mechanisms : Disruption of lipid containing cell membrane. Modification of proteins Modification of DNA. But some chemicals act by more than one mechanism. Chemicals may be either fluid or gases.

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Disruption of lipid containing cell membrane Alcohol Required presence of the water for maximal activity It also denture proteins. Used as antiseptic to clear the skin prior to venipuncture Detergents Composed of long chain of lipid soluble , hydrophobic portion and a polar hydrophilic group. Interact with the lipid in the cell membrane through their hydrophobic chain and with surrounding water through their polar group Quaternary ammonium e.g. benzal - konium used as skin antiseptic .

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Phenols it is also denature proteins . e.g. cresol Modification of proteins Chlorine purify the water supply and to treat swimming pools. the active component of hypochlorite which is used in homes and hospitals . Heavy metals - Mercury and silver have the greatest anti bacterial activity . - They act by binding to sulfhydryl , blocking enzymatic activity.

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Iodine The most effective skin anti septic . used as prior to obtaining a blood culture and installing intravenous catheters . iodine is supply in two forms : tincture of iodine it is used to prepare skin prior to blood culture . Because tincture of iodine is irritating it should be remove with alcohol Iodophors is complex of iodine and detergents use to prepare skin prior to surgery . They act by binding to sulfhydryl , blocking enzymatic activity.

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Hydrogen peroxide Used for cleaning wounds . It is effectiveness is limited by organisms ability to produce catalase They act by binding to sulfhydryl , blocking enzymatic activity. Formaldehyde and glutaraldehyde - they also denature nucleic acid - Glutaraldehyde has two aldehyde groups it is 10 times more effective than formaldehyde and less toxic . In hospitals it is used to sterilize respiratory therapy equipments .

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Ethylene oxide Used in hospitals for sterilization of heat sensitive materials It is denature nucleic acid Acids and alkalis Modification of nucleic acid A verity of dyes not only stain microorganisms but also inhibit their growth one of these is crystal violet .

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Quality control

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Proper sterilization of instruments and materials is a critical aspect of infection control. sterility assurance program involves the use of the following management tools: Mechanical/Electronic Controls Chemical Indicators/Integrators Biological Indicators (spore tests) Sterilizer Maintenance Record Keeping

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Mechanical/Electronic Controls The easiest . Most older sterilizers use analog (mechanical) controls, while newer sterilizers usually have digital (electronic) controls. Compared to analog controls, digital controls have proven to be much more reliable; therefore, you should upgrade where possible. new technology digital monitoring systems available that monitor all the parameters of the sterilization process through a real time system with adjustable alarms to alert the user to any changes to the vessel, pumps, valves or temperature variances. These systems graph the physical parameters of the sterilization process.

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Chemical Indicators/Integrators In expensive . Some chemicals change their color at certain temperature . E.g. Brown discovered away and made tubes called Brown's tubes that contain a red liquid . When we put it in the autoclave . After sterilization if its proper the color change from red to green . e.g. Bowie-Dick tape Is a brown tape we put it in the article , after efficient sterilization black lines appears . It is modified to appear as letters instead of lines . After a successful sterilization appear the word sterile .

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Biological Indicators (spore tests) Involve the use of bacterial spores considered the highest level of sterility assurance because they actually test the sterilizer's ability to kill specific strains of highly resistant organisms. available in the following 4 forms 1- Spore strips are available in a variety of concentrations and spore populations allowing the user to select a specific SAL (sterility assurance level). After processing, the spore strip envelope is opened and the BIs aseptically transferred into a tube of sterile culture media, then incubated for up to 7 days

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Control Un exposed spore + nutrient media Growth Test exposed spore + nutrient media Growth Positive Not sterile No Growth negative sterile

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2- Self-Contained vials are available as single or dual species for use with Steam or EO gas processes. A glass ampoule of sterile media is surrounded by a plastic vial with a spore strip inside. After processing, the user activates the BI by crushing the vial (manually or with a device) to let the media come into contact with the spore strip

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Control Un exposed spore + nutrient media Growth Test exposed spore + nutrient media Growth Positive Not sterile No Growth negative sterile

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3- Sealed Glass Ampoules This form has the spores and media mixed together; therefore, no vial crushing or activation is required after processing. Control Un exposed spore + nutrient media Growth Test exposed spore + nutrient media No Growth negative sterile Growth Positive Not sterile

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4- Spore Suspension is available in 10 ml pharmaceutical vials directly from Manufacturers and is used for cycle and/or direct inoculation of product for process validation. Geobacillus stearothermophilus , Bacillus atrophaeus and B. pumilus spores are commonly stocked by suppliers. Positive biological indicator -When the result is Positive BIs the following actions should be taken: - Report results to supervisor - Recall and resterilize all "suspected non-sterile" items - Verify spore growth via gram stain -Determine cause of failure and correct - Retest sterilizer before using again

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Sterilizer Maintenance The following maintenance procedures are considered the fourth management tool: Routine Maintenance - daily inspections and cleaning in accordance with the manufacturer's recommendations. This generally includes the cleaning of gaskets, chart pens, chamber drain screens and internal/external surfaces. Preventive Maintenance - periodic preventive maintenance in accordance with the manufacturer's instructions.

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Scheduled Maintenance - this level of maintenance should include lubrication of appropriate parts and replacement of expendable parts, i.e. steam traps. Calibration - periodic calibration of items such as pressure and temperature gauges, timers, recording and control devices must be carried out by qualified personnel as specified in the manufacturer's instruction manual.

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Record Keeping The fifth management tool is Record keeping, which is considered an absolute essential for any facility involved in the sterilization of instruments and materials for disbursement. all sterilization records should include the following: -Date, sterilizer #, load # - Lot number, general contents of load - Exposure time, temperature & pressure - Operator's name or initials - Chemical indicator results - Biological indicator results - Bowie-Dick test results (Steam vacuum)

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