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Physical sterilization
(1) Heat sterilization method <br> Heating can destroy enzymes, proteins and nucleic acids in microorganisms, resulting in the death of microorganisms. Heat sterilization is divided into dry heat sterilization and moist heat sterilization. At the same temperature, the effect of moist heat sterilization is better than dry heat sterilization. Mainly due to the presence of moisture during sterilization by moist heat, the protein is easily denatured. Moisture is also easy to wet the microbial membrane wall, and the penetration of moist heat is greater than dry heat.
Dry heat sterilization methods are commonly used in flame sterilization and dry hot air sterilization.
(2) UV sterilization method <br> refers to the method of killing microorganisms by ultraviolet radiation. The ultraviolet wavelength generally used for sterilization is 200 to 300 nm, and the wavelength with the strongest sterilization power is 253.7 nm. Ultraviolet light acts on nucleic acid proteins to cause denaturation, and at the same time, the air is exposed to ultraviolet rays to generate trace amounts of ozone, thereby co-sterilizing. Ultraviolet light travels in a straight line and can be reflected by different surfaces. The penetration is weak, but it is easier to penetrate clean air and pure water. Therefore, the method is applicable to the sterilization of the surface of the irradiated object, the sterilization of the air and water in the sterile room; the sterilization of the liquid medicine and the sterilization of the deep solid material; the ordinary glass absorbs the ultraviolet light, so it is installed in the glass container. The drugs in this medicine cannot be sterilized by this method. Ultraviolet rays are exposed to the human body for a long time, and conjunctivitis, erythema and skin burning may occur. Therefore, the ultraviolet light is usually turned on for 1 to 2 hours before the person enters the room, and the talent enters the clean room after being closed. If ultraviolet disinfection must be carried out after the person has entered, the human skin and eyes should have effective protective measures. Generally, a 30-watt UV lamp can be installed in a space of 6 to 15 m3, preferably 2.5 to 3 m from the ground.
Pay attention to the following problems when sterilizing with ultraviolet radiation:
1. The bactericidal power of ultraviolet light decreases with the increase of the use time. When the normal use time reaches 70% of the rated time, the ultraviolet lamp should be replaced to ensure the sterilization effect. The average life of domestic UV lamps is generally 2000h.
2, the bactericidal effect of ultraviolet light varies with the strain, the amount of mold killing is 40 to 50 times larger than the bacillus.
3. Ultraviolet radiation is usually designed on the basis of a relative humidity of 60%. When the indoor humidity increases, the exposure should be increased accordingly.
4, the effect of ultraviolet sterilization is related to the length of the irradiation, which requires verification to determine the irradiation time.
5. The installation form and height of the UV irradiation lamp should be determined according to the actual situation and with reference to the instructions for use.
The validation of the sterilization method uses a biological indicator challenge test, and the biological indicator uses a Bacillus subtilis.
(3) Microwave sterilization method <br> Microwave refers to electromagnetic waves with a frequency between 30 and 3000 MHz. Water can strongly absorb microwaves, rotate its polar molecules, generate heat by friction between molecules, and heat up rapidly, sterilizing by heat. It can reach 100-150 ° C in tens of seconds to several minutes, and all kill microorganisms in the liquid, suitable for sterilization of water-soluble injection. In addition, the solid medicine decoction pieces and solid preparations (pills, powders, capsule powders, etc.) also contain a small amount of water, and the microwave energy can penetrate into the solid interior, and is uniformly heated from the surface to the inside, and functions as a drying and sterilization. It is mostly used for the sterilization of oral liquid preparations and is expected to be used for sterilization of injection liquids. However, it may affect the PH value, content and color of certain drugs.
(4) Radiation sterilization method <br> Radiation sterilization is a method of killing bacteria by using γ-rays and β-rays. It is also called ionizing radiation. The former is emitted by cobalt-60 or 铯-137, and the penetration is strong; The electron accelerator generates, has a charge, has weak penetrating power, and has poor sterilization effect.
Chemical Sterilization <br> Chemical sterilization refers to the use of chemicals to kill microorganisms. The same chemical exhibits a bacteriostatic effect at a low concentration and a bactericidal action at a high concentration. The bactericidal mechanism may be: denaturation of the microbial protein, or interaction with the enzyme system to affect metabolism, or change the permeability of the membrane wall to cause microbial death. Commonly used methods include disinfectant disinfection and chemical gas sterilization.
(1) Disinfectant disinfection method <br> Disinfection refers to the method of killing pathogenic microorganisms. However, most chemical disinfectants can only kill the propagules of microorganisms and cannot kill spores, and can control a certain range of sterilized state. The disinfectant can be formulated into a suitable concentration, and the materials, environment, appliances, etc. can be disinfected by spraying, rubbing or soaking. Commonly used chemical disinfectants are 0.1% to 0.2% benzalkonium bromide solution, 3% to 5% phenol or coal phenol soap solution, 75% ethanol, and the like. Commonly used for surface sterilization of objects. However, be careful not to over-concentrate it to prevent chemical corrosion. Clean room walls, ceilings, doors and windows, machinery and equipment, instruments, consoles, cars, tables, chairs and other surfaces as well as human hands (gloves) should be cleaned regularly and sprayed with disinfectant during environmental verification and daily production. The disinfectant used must be in a laminar flow table and filtered with a 0.22 μm filter before it can be used.
(2) Chemical gas sterilization method <br> refers to a method for killing microorganisms by using a chemical gas or generated steam.
Ethylene oxide sterilization
The ethylene oxide sterilization method is a method of sterilizing using ethylene oxide gas. It is a traditional sterilization method, which can be applied to sterilization of work clothes sterilization, medicines that are not resistant to heat sterilization, medical instruments, facilities, equipment, and the like.
The ethylene oxide sterilization system mainly has the following four important factors that restrict each other:
1 temperature; 2 humidity; 3 gas concentration; 4 sterilization time.
Because ethylene oxide is a flammable and explosive substance, an open flame can cause combustion, and at the same time, it may cause an explosion due to gas decomposition. Safety concerns should be paid attention to in the sterilization of ethylene oxide.
2. Formaldehyde and other steam fumigation methods
The use of formaldehyde, propylene glycol or peracetic acid and other chemicals, steam generated by heating for air environment sterilization.
(1) Calculate the volume of the room and weigh out the formaldehyde at a rate of 10 g/m3.
(2) Pour formaldehyde into the formaldehyde generator or heating plate or beaker, and put the humidification water, if necessary, add potassium permanganate (2~3g/m3), then heat (the formaldehyde generator is heated by steam, The heating plate or beaker is heated with water therein to evaporate it into a gas.
(3) Sterilization process: the air conditioner stops running → start the formaldehyde gas generator or heat the formaldehyde in the heating plate → let the formaldehyde gas spread for about 30 minutes → start the air conditioner to let the formaldehyde gas circulate for about 30 minutes → stop the air conditioner, the room Fumigation, no less than 8 hours → Room exhaust, replaced with fresh air for about 2 hours → resume normal operation.
When the relative humidity is above 65% and the temperature is between 24 and 40 °C, the disinfection effect of formaldehyde gas is the best.
3. Ozone disinfection method The principle of ozone (O3) disinfection is: ozone has unstable molecular structure at normal temperature and pressure, and quickly decomposes into oxygen (O2) and single oxygen atom (O). The latter has strong activity. It has a strong oxidizing effect on bacteria, which oxidizes and decomposes the enzymes necessary for oxidizing glucose inside the bacteria, thereby destroying its cell membrane and killing it. The excess oxygen atoms recombine themselves into universal oxygen molecules (O2) without any harmful residues, so they are called non-polluting disinfectants. It not only has strong killing ability against various bacteria (including hepatitis virus, Escherichia coli, Pseudomonas aeruginosa and bacteria), but also is effective for mold.
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Summary of several commonly used sterilization methods
Summary of several commonly used sterilization methods