Lecture 19Outline of Last Lecture 1. Genome2. Mutation3. Gene Transfer Systems & RecombinationOutline of Current Lecture 1. Controlling Microorganisms2. Terminology3. Microbial Death4. Concerns of Microbial ControlCurrent LectureChapter 7—Control of MicrobesControlling MicroorganismsDecontamination: Use of physical, chemical, and mechanical methods to destroy or reduce undesirable microbes in given areaPrimary targets are microorganisms capable of causing infection or spoilage:- Vegetative bacterial cells & endospores- Fungal hyphae and spores, yeast- Protozoan trophozoites and cysts- Worms- Viruses- PrionsDisinfection: The destruction or removal of vegetative pathogens, but not bacterial endospores. Usually used only on inanimate objects (cleaning toilet, countertops)Sterilization: Complete removal or destruction of all viable microorganisms. Used on inanimate objects (include endospores + viruses)Antisepsis: Chemicals applied to body surfaces to destroy or inhibit vegetative pathogensTerminology & Methods of ControlSporicidal- Ability to kill bacterial endospores. Sterilizing agent if with 3 belowBactericide- clear all vegetative cells, not spores BSC 160 1nd EditionFungicide- Kill fungusViruscide- Inactivate virus, Virus cannot infect new host (treat tissues)- -cide: to killAntiseptic- Disinfectant that can be applied to expose surfaces (tissues but not directly)Sepsis- Bad thing; infection in blood (all over)Asepsis- Practice that restricts entry of infectious agent, Prevents infectionSanitization- Mechanically removing microbes cleaning techniquesDegermination- Mechanically reducing microbial loadMicrobial Death—How do you know?- Permanent & complete loss to reproduce = Dead- Under optimal growth conditionsFactors that affect microbial death rate:- # of microbes- Nature of microbes- Temperature + pH- Concentration/dose of agent- Mode of action of agent- Solvents, organic materials, or inhibitorsPractical Concerns in Microbial ControlSelection of method of control depends on circumstances:- Does the application require sterilization?- Is the item to be reused?- Can the item withstand heat, pressure, radiation, or chemicals?- Is the method suitable?- Will the agent penetrate to the necessary extent?- Is the method cost- and labor-efficient and is it safe?Relative Resistance of MicrobesHighest resistance: Prions, bacterial endosporesModerate resistance: Pseudomonas sp., Mycobacterium tuberculosis, Staph aureas, Protozoan cystsLeast resistance: Most bacterial vegetative cells, fungal spores & hyphae, yeast, enveloped viruses & protozoan trophozoitesMethods of Physical Control- Heat—Moist & dryo Incineration: Make it go away- Cold temperatures- Desiccation- Radiation- FiltrationIonizing radiation- Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA. Gamma rays, X-rays, cathode rays- Used to sterilize medical supplies & food
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