Microbio 310 1st Edition Lecture 21 Outline of Last Lecture I. 16.9 Applications of SSU rRNA Phylogenetic MethodsII. 16.10 Phenotypic AnalysisIII. 16.11 Genotypic AnalysisOutline of Current Lecture I. Facts about Antibiotics/ResistanceII. 26.1 Heat SterilizationIII. 26.2 Radiation SterilizationIV. 26.3 Filter SterilizationV. 26.4 Chemical Growth ControlCurrent LectureHow Antibiotic Resistance Happens1. Lots of Germs. A few are drug resistant.2. Antibiotics kill bacteria causing the illness, as well as good bacteria protecting the body from infection.3. The drug resistant bacteria are now allowed to grow and take over.4. Some bacteria give their drug-resistance to other bacteria, causing more problems.- You kill off the competitors of the MOST drug-resistant bacteria by not taking your antibiotics for the full amount of time.Antibiotics in Food Supply- 80% of all antibiotics are used on factory farm animals.- Pros– 4-5% increase in feed conversion rate– Increase in lifespanThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.– Disease suppression– Shelf-life of meat, poultry, and eggs- Cons– Selection for multi-drug resistant (MDR) pathogens– MDRs are a result of antibiotic feed– Food supply contaminated with drug resistant pathogens26.1 Heat Sterilization• Heat sterilization is the most widely used method of controlling microbial growth autoclave– High temperatures denature macromolecules• Some bacteria produce resistant cells called endospores– Can survive heat that would rapidly kill vegetative cells• The autoclave is a sealed device that uses steam under pressure– Allows temperature of water to get above 100C – Not the pressure that kills things, but the high temperature• Pasteurization is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids– Does NOT kill all organisms, so it is different than sterilization – Ultra High Temp (UHT) shelf stable (longer shelf life) milk26.2 Radiation Sterilization• Microwaves, UV, X-rays, gamma rays, and electrons can reduce microbial growth• UV has sufficient energy to cause modifications and breaks in DNA– UV is useful for decontamination of surfaces– Cannot penetrate solid, opaque, or light-absorbing surfaces– Cooley Dickinson Roboto Portable UV source; only where UV light hits it can sterilize surfaces• Ionizing radiation– Electromagnetic radiation that produce ions and other reactive molecules– Generates electrons, hydroxyl radicals, and hydride radicals– IRRADIATED no contact NOT RADIOACTIVE• Sources of radiation include cathode ray tubes, X-rays, and radioactive nuclides• Radiation is used for sterilization in the medical field and food industry– Radiation is approved by the WHO and is used in the USA for decontamination of foodsparticularly susceptible to microbial contamination• Hamburger, chicken, spices may all be irradiated26.3 Filter Sterilization• Filtration avoids the use of heat on sensitive liquids and gases– Pores of filter are too small for organisms to pass through– Pores allow liquid or gas to pass through• Depth filters– HEPA filters- Membrane filters – Function more like a sieve• Membrane filters– Filtration can be accomplished by syringe, pump, or vacuum– A type of membrane filter is the nucleation track (nucleopore) filter26.4 Chemical Growth Control• Antimicrobial agents can be classified as bacteriostatic (slow it down), bacteriocidal (kill it), and bacteriolytic (bust it open)• Unknown infection, Monitoring, Patient toxicity- Minimum inhibitory concentration (MIC) is the smallest amount of an agent/drug needed toinhibit growth of a microorganism– Varies with the organism used, inoculum size, temp, pH, etc.• Disc diffusion assay– Antimicrobial agent added to filter paper disc– MIC is reached at some distance• Zone of inhibition– Area of no growth around disc– Can be quantified: diameter of circle is proportional to the amount of antimicrobial agent added to the disc, the solubility of the agent, the diffusion coefficient, and the overall effectiveness of the