【正文】 probably 1,000 of them are used routinely in the allied health sciences and the home. ? Antimicerobial chemicals occur in the liquid, gaseous, or even solid state and vary from disinfectantes and antiscptics to sterilantes and preservatives. For the sakeof convenience many solid or gaseouse antimicrobial chemicals are dissolved in water, alcohol, or a mixture of the two to produce a liquid solution. CHOOSING A MINCROBICIDAL CHEMICAL ? The choice and appropriate use of a antimicrobial chemical agents is of constant concern in medicine. Although actual clinical practices of chemical decontamination vary widely, some desirable qualities in a germicide have been identified, including: 1. rapid action even in low concentrations, 2. solubility in water or alchol and longterm stability, 3. broadspectrum micerobicidal action without being toxic to human and animal tissues, 4. peration of inanimate surfaces to sustain a cumulative(累積的 ) or persistent action, 5. resistance to being inactivated by anic matter, 6. noncorrosive(非腐蝕性的 ) or nonstaining properties, 7. Sanitizing（消毒 ） and deodorizing（除臭 ） properties,and 8. inexpensiveness and ready availability. ? Germicides（殺菌劑 ） are evaluated in terms of their effectiveness in destroying microbes in medical and dental（牙齒的 ） settings. The three levels of chemical deamination(凈化 ) procedurces are high, intermediate, and low (table ).Highlevel germicides cill endospores,and,if properly used, are sterilants. ? Materials that access it at highlevel control are medical Devices—for example, catheters(醫(yī)用導(dǎo)管 ), heartlung Equipment, and implants—that are heatsterilizable and are intended to enter body tissues during medical procedures. Intermediatelevel germicides kill fungal (but not bacterial) sporec, resistant pathogens. ? Low levels of disinfectipn eliminate only vegetative bacteria, vegetative fungal cells, and some viruses. They are used to clean materials such as electrodes(電極 ), and furniture that touch the skin surfaces. FACTORS THAT AFFECT THE GERMICIDAL ACTIVITY OF CHEMICALS ? Factors that control the effect of a germicide include the nature of the microanisms being treated, the nature of the material being treated, the degree of contamination, the time of exposure, and the strength and chemical action of the germicide. ? A chemical’ s strength or concentration is expressed in various ways, depending upon convention and the method of preparation. The content of many chemical agents can be expressed by more than one notation. 謝謝觀看 /歡迎下載 BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH 。 most disinfectants are more active at higher concentrations. 5. The mode of action of the agent (). How does it kill or inhibit the microanism? 6. The presence of solvents（有溶解力的） , interfering anic matter, and inhibitors. Large amounts of saliva, blood, and feces can inhibit the actions of disinfectants and heat. HOW ANTIMICROBIAL AGENTS WORK: THEIR MODES OF ACTION ? An antimicrobial agent’ s adverse（不利的） effect on cells is known as its mode of action. Agents affect one or more cellular targets, inflicting damage progressively until the cell is no longer able to survive. Antimicrobials have a range of cellular targets, with the agents that are least selective in their targeting tending to be effective against the widest range of microbes. ? The cellular targets of physical and chemical agents fall into four general categories: 1. the cell wall. 2. the cell membrane. 3. cellular synthetic processes (DNA,RNA), and 4. proteins. The Effects of Agents on the Cell Wall ? The cell wall maintains the structural integrity of bacterial and fungal cells. Several types of chemical agents damage the cell wall by blocking its synthesis, digesting it, or breaking down its surface. A cell deprived of a functioning cell wall bees fragile(脆弱的 ) and is lysed（溶解） very easily. How Agents Affect the Cell Membrane ? All microanisms have a cell membrane posed of lipids and proteins, and we learned in previous chapter, a cell’ s membrane provides a twoway system of transport. If this membrane is disrupted, a cell loses its selective permeability（透過性 ） and can neither prevent the loss of vital molecules nor bar the entry of damaging chemicals. Agents That Affect Protein and Nucleic Acid Synthesis ? Microbial life depends upon an orderly and continuous supply of proteins to function as enzymes and structural molecules. As we saw in chapter 9, these proteins are synthesized on the ribosomes through a plex process called translation. For example, the antibiotic choramphenicol（氯霉素） binds to the ribosomes of bacteria in a way that stops peptide bonds from forming proteins required in growth and metabolism and are thus inhibited from multiplying. ? The nucleic acids are likewise necessary for the continued functioning of microbes. Some agents bind irreversibly to DNA, preventing both transcription and translation。 C for 35 minutes. Flow of Normal Autoclaving Water is boiling 水加熱到沸騰 Turn Off the Valve 關(guān)閉排氣閥 Increasing and Maintaining Pressure in the Specific Time升壓、定時(shí)保壓 Decreasing Pressure and Discharging Water Vapour降壓并排出蒸汽 If you just turn off the valve before boiling. Result ? ? ? ? Water Vapour Cool Air Water Vapour A： 110℃ ， B： 121 ℃ ， Pressure:There is no