Lecture 171. Understand the difference between pasteurization and sterilization a. Pasteurization- Reduction of the population of undesirable microbes in a heat- sensitive liquid. Used for milk and other heat sensitive foodsb. Sterilization- Kills every organism, bacteria virusi. Autoclaving- sterilization by heat. Time for a given species in 12xD2. Calculate the standard killing time for a microbe given its decimal reduction time a. The decimal reduction time (D) at a given temperature is the time requiredto reduce the number of live bacteria 10-fold. i. 10-fold reduction = reduction by 90%ii. you have 10% of the population left b. Decimal reduction time is species specific3. Understand why heat sterilization is done under high pressure a. Prevents any boilingb. 15lb/in24. Compare and contrast sterilization by UV radiation on one hand and by electron beam or gamma rays on the other hand a. UV lighti. DNA damageii. Disinfection of exposed surfaces, air, wateriii. Used for reducing microbial contaminants on surfacesb. Gamma rays or X-raysi. Damage to DNA and proteins via electrons and radicalsii. Sterilization of medical devices, bulk foodsiii. Sterilization of medical devices and food5. List applications of sterilization by radiation a. UV lightb. Gamma rays or X-rays (ionizing)6. Calculate the standard killing dose for a microbe given its decimal reduction time a. 12 x D7. Compare and contrast depth filters and membrane filters a. Depth filters:i. Sheets or mats of fibrous paper, cellulose, or glass that resist clogging.ii. Prefilters to remove big cloggingiii. Do not sterilize because their pores are too bigb. Membrane Filtersi. Uniform pore sizeii. Used for sterilizationiii. Most commonly used filters in microbiologyiv. Typically 0.2 um and 0.45 um pore size8. Explain why depth filters are often used a prefilters before sterilizing with membrane filters a. They remove big particles 9. Compare and contrast chemical non-chemotherapeutic and chemotherapeutic agents a. Non- chemotheraprutic agentsi. Non-selective agents: have similar effects on all cellsii. Used to inhibit or kill microbes on living surfaces (topically) or inanimate objectsiii. Too toxic for use inside the human bodyb. Chemotherapeutic agentsi. Selective agents: kill specific microbes but do not kill the hostii. Can be used internally to control microorganisms that cause infectious diseasesiii. Include antibacterial (antibiotics), antifungal, and antiviral drugs10. Name and rank the three main classes of chemical non-chemotherapeutic agents based on their strength a. Sterilizersi. Purpose: Kill all living organisms including sporesii. Use: Hospital lab equipment and heat sensitive instrumentsiii. Examples: Ethylene oxide (gas), Formaldehyde (gas), Hydrogen peroxide (vapor)iv. REMEMBER: GASb. Disinfectants i. Purpose: Kill microbes in inanimate surfaces, may not kill sporesii. Use: Hospital, medical, homesiii. Examples: Alcohol (60-85%), cationic detergents, chlorine compounds, ozone, formaldehyde (dilute solution)c. Sanitizersi. Purpose: Reduce, but may not eliminate all microbesii. Uses: Food and food prep industriesiii. Examples: Cationic detergents, chlorine compounds, iodine containing compounds. All more dilute and shorter application timesthan for disinfecting usesd. Antisepticsi. Purpose: Non toxic can be used on the surface of living tissuesii. Use: Wound or surgical sitesiii. Examples: Alcohol (60-85%), cationic detergents, hydrogen peroxide (dilute), iodine containing compounds11. Compare and contrast antiseptics and chemotherapeutic agents a. Antiseptics you can sue on the skin12. Compare and contrast bacteriostatic, bacteriocidal, and bacteriolytic agents a. Bacteriostatic - static, means to stop but not killb. Bacteriocidal – cidal means to kill, but not to lysec. Bacteriolytic - lytic means to lyse (thus to kill)13. List factors that influence the effectiveness of a chemical antimicrobial agent a. Microbial factors:i. Population sizeii. Encasement within surface biofilmsiii. Microbial resistance b. Antimicrobial treatment factors:i. Antimicrobial concentrationii. Duration of treatmentiii. Temperature of treatmentiv. Presence of organic
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