BSC 160 1nd Edition Lecture 19 Outline of Last Lecture 1 Genome 2 Mutation 3 Gene Transfer Systems Recombination Outline of Current Lecture 1 Controlling Microorganisms 2 Terminology 3 Microbial Death 4 Concerns of Microbial Control Current Lecture Chapter 7 Control of Microbes Controlling Microorganisms Decontamination Use of physical chemical and mechanical methods to destroy or reduce undesirable microbes in given area Primary targets are microorganisms capable of causing infection or spoilage Vegetative bacterial cells endospores Fungal hyphae and spores yeast Protozoan trophozoites and cysts Worms Viruses Prions Disinfection 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 pathogens Terminology Methods of Control Sporicidal Ability to kill bacterial endospores Sterilizing agent if with 3 below Bactericide clear all vegetative cells not spores Fungicide Kill fungus Viruscide Inactivate virus Virus cannot infect new host treat tissues cide to kill Antiseptic 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 infection Sanitization Mechanically removing microbes cleaning techniques Degermination Mechanically reducing microbial load Microbial Death How do you know Permanent complete loss to reproduce Dead Under optimal growth conditions Factors 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 inhibitors Practical Concerns in Microbial Control Selection 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 Microbes Highest resistance Prions bacterial endospores Moderate resistance Pseudomonas sp Mycobacterium tuberculosis Staph aureas Protozoan cysts Least resistance Most bacterial vegetative cells fungal spores hyphae yeast enveloped viruses protozoan trophozoites Methods of Physical Control Heat Moist dry o Incineration Make it go away Cold temperatures Desiccation Radiation Filtration Ionizing 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 products
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