MicrobiologySterilizationandDisinfection.pptVIP

Microbiology Chapter 12Sterilization and Disinfection Microbiology 130 R.L. Brashear-Kaulfers Principles of Sterilization Disinfection Disinfectants-applied to inanimate objects Antiseptics- applied to living tissue Some can be used as both Sterilization- killing or removal of all microorganisms in a material or on an object Sterility- no living organisms on/in object Disinfection- reducing the # of pathogenic organisms on object or in material, so they pose no threat of disease Control of Microbial Growth 1out of 1 million probability is sterile 1)Total # of microbes present affects the length of time needed to eliminate them 2) Fewer organisms present, shorter time needed for sterility Different microbial agents affect differently Most susceptible phase is logarithmic phase 3) Microorganisms differ in their susceptibility to antimicrobial agents Chemical Antimicrobial Agents Potency or effectiveness of Chemical Agents: Bactericidal- killing Bacteriostatic- growth inhibiting Ethyl and isopropyl alcohol- 70% effective as it can penetrate more deeply Evaluating Effectiveness * Phenol coefficient- compare to phenol (carbolic acid) =1 higher is more effective, lower is less effective Use with Staph typhi and Staph aureas standards Used to research new disinfectants, but has problems * Filter Paper Method- uses small filter disks And look for zone of inhibition-shows some effectiveness but organic matter may interfere with results * Use-Dilution test: standard prep of bacteria , coated on stainless steel and dipped into dilutions of agents, incubated and observed for no growth* better results than phenol test Disinfectant Selection-Several Qualities 1) Should be fast acting in presence of organic substances 2) Be effective against all types of infectious agents without destroying tissue or acting as a poison if ingested 3) Easily penetrate material to be disinfected, without damaging/discoloring it 4) Be easy to prepare, stable when exposed to light, heat or othe