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1、Chapter Overview The control of microbes in the environment is a constant concern of health care and industry since microbes are the cause of infection and food spoilage(破坏), among other undesirable events. Antimicrobial control is accomplished using both physical technique and chemical agents to de
2、stroy, remove, or reduce microbes in a given area. Many factors must be contemplated（关注 ） when choosing an antimicrobial technique, including the material being treated, the type of microbes involved, the microbial load, and the time available for treatment. Antimicrobial agents damage microbes by d
3、isrupting the structure of the cell wall or cell membrane ,preventing synthesis of nucleic acids （DNA and RNA）, or altering the function of cellular proteins .Microbicidal agents kill microbes by inflicting nonreversible（不可逆的） damage to the cell .microbistatic agents temporarily inhibit the reproduc
4、tion of microbes but do not inflict irreversible damage .Mechanical antimicrobial agents physically remove microbes from materials but do not necessarily kill or inhibit them. Heat is the most physical agent in microbial control and can be delivered in both moist (steam sterilization, pasteurization
5、) and dry forms. Radiation exposes material to high energy waves that can enter and damage microbes. Examples are ionizing and ultraviolet radiation. Chemical antimicrobial are available for every level of microbial treatment, from low -level disinfectants to high-level sterilants. Antimicrobial che
6、mical include halogens, alcohols, phenolics, peroxides, heavy metals, detergents, and aldehydes.Controlling Microorganisms Controlling our degree of exposure to potentially harmful microbes is a monumental（非常的） concern in our lives, and it has a long and eventful（ 重大的） history.GENERAL CONSIDERATIONS
7、 IN MICROBIAL CONTROL The methods of microbial control belong to the general category of decontamination（净化） procedures, in that they destroy or remove contaminants. Most decontamination methods employ either physical agents, such as heat or radiation, or chemical agents such as disinfectants and an
8、tiseptics（无菌的 ）.RELATIVE RESISTANCE OF MICROBIAL FORMS The primary targets of microbial control are microorganisms capable of causing infection or spoilage that are constantly present in the external environment and on the human body . This targeted population is rarely simple or uniform; in fact, i
9、t often contains mixtures of microbes with extreme difference in resistance and harmfulness. Contaminants that can have far-reaching effects if not adequately controlled include bacterial vegetative cells and endospores, fungal hyphae and spores, yeasts, protozoan trophozoites（滋养体 ） and cysts, worms
10、, insects and their eggs, and viruses. This scheme compares the general resistance these forms have to physical and chemical methods of control: Highest resistance Bacterial endospores Moderate resistance Protozoan cysts: some fungal sexual spores (zygospores接合孢子);some viruses. In general, naked vir
11、uses are more resistant than enveloped forms. Least resistance Most bacterial vegetative cells; fungal spores and hyphae; enveloped viruses; yeasts; and protozoan trophozoites. Actual comparative figures on the requirements for destroying various groups of microorganisms are shown in table 11.1TERMI
12、NOLOGY （术语）AND METHODS OF MICROBIAL CONTROL Through the years, a growing terminology has emerged for describing and defining measures that control microbes. To complicate matters, the everyday use of some of these terms can at times be vague and inexact. Sterilization Sterilization is a process that
13、 destroys or removes all viable microorganisms, including viruses. Any material that has been subjected to this process is said to be sterile. Sterilized products are essential to human well-being. Although most sterilization is performed with a physical agent such as heat, a few chemical called ste
14、rilants can be classified as sterilizing agents because of their ability to destroy spores. At times, sterilization is neither practicable nor necessary, and only certain groups of microbes need to be controlled. Keep in mind that the destruction of spores is not always a necessity SterilizationHigh
15、 Temperature （高温）Ultraviolet Rays （紫外线）High temperature can make protein、 nucleic acid（核酸） 、 lipid（脂类） and other macromolecules（生物大分 子） to degraded （降解）、 denaturalized（变性） and destoryed.High TemperatureHigh Temperature SterilizationDry Heat Sterilization (干热空气灭菌法)Moist Heat Sterilization (湿热空气灭菌法)Flame Burn （灼烧 ）High Temperatue in Oven （干热空气 灭菌）Normal PressureHighPressurePasteurization (巴氏消毒法)Boiling（煮沸法 ）Tyndallization (间歇灭菌法)Continuous Pressure Sterilization（连续高压灭 菌）Normal PressureHigh PressureNormal Pressure Sterilization（常压灭菌 ）Flame BurnOese(接种环) High Temperatue in Oven Oven（烘箱）Culture
