醫(yī)藥實(shí)驗(yàn)室微生物消毒滅菌和生物安全
發(fā)布時(shí)間：
2022-11-16
作者：
醫(yī)藥實(shí)驗(yàn)室微生物消毒滅菌和生物安全：微生物易受外界條件的影響，如果環(huán)境適宜，可促進(jìn)微生物的生長繁殖；劇烈的環(huán)境變化則可使微生物生長受到抑制甚至死亡。由于微生物廣泛存在于自然界，其中有些又是病原微生物，因此，從預(yù)防感染和避免實(shí)驗(yàn)室微生物污染的角度出發(fā)，醫(yī)務(wù)工作者及相關(guān)科研人員必須牢固樹立無菌觀念和嚴(yán)格執(zhí)行無菌操作。例如醫(yī)療器械，手術(shù)室和無菌室等均需用適宜的方法進(jìn)行消毒或滅菌。為防止疾病傳播，對于傳染病患者的排泄物以及實(shí)驗(yàn)室廢棄的培養(yǎng)物也要進(jìn)行消毒或滅菌處理。消毒與滅菌是臨床醫(yī)學(xué)和微生物學(xué)中十分重要的基本操作技術(shù)，采用的方法不同，達(dá)到的效果也有差異。以下是有關(guān)消毒滅菌的常用術(shù)語。
1．消毒（disinfection）指殺滅物體上或環(huán)境中病原微生物的方法，但不1定能殺死細(xì)菌芽胞或非病原微生物，如飲用水的消毒。用于消毒的化學(xué)藥品稱為消毒劑（disinfectant）。
2．滅菌（sterilization）指殺滅或清除物體上所有微生物的方法，包括全部病原微生物和非病原微生物以及細(xì)菌芽胞。如注射用生理鹽水，外科用敷料和培養(yǎng)基均需要滅菌后使用。一般選物理方法進(jìn)行滅菌。
3．防腐（antisepsis）是指在體外防止或抑制細(xì)菌生長繁殖的方法。細(xì)菌一般不死亡，如生物制劑中加入0.01%硫柳汞可防止雜菌生長。同1種化學(xué)藥品在高濃度時(shí)為消毒劑，低濃度時(shí)可作為防腐劑。抗生素可抑制細(xì)菌的生長繁殖稱之為抑菌（bacteriostasis），這些抗生素被稱作抑菌劑（bacteriostat）。在體內(nèi)抑制細(xì)菌的繁殖,在體外可用于抑菌試驗(yàn)以檢測細(xì)菌對抗生素的敏感性。
4．無菌（asepsis）及無菌操作(aseptic technique)無菌指不存在活的微生物，為滅菌的結(jié)果。防止微生物進(jìn)入人體或污染物品的操作技術(shù)，稱為無菌操作。如在進(jìn)行外科手術(shù)時(shí)需要防止細(xì)菌進(jìn)入創(chuàng)口，微生物學(xué)實(shí)驗(yàn)操作中要注意防止微生物的污染和感染。
第1節(jié) 物理消毒滅菌法
消毒與滅菌方法一般分為物理方法與化學(xué)方法兩大類。用于消毒滅菌的物理因素主要有熱力，輻射，濾過除菌，超聲波，低溫和干燥等方法。
1，熱力滅菌法
高溫對微生物有明顯的致死作用，其主要是通過變性蛋白質(zhì)，破壞細(xì)胞膜和降解核酸達(dá)到殺菌作用，因而常用于消毒和滅菌。熱力滅菌法分為干熱滅菌和濕熱滅菌兩大類，在同1溫度下，濕熱滅菌的效力優(yōu)于干熱滅菌，這是因?yàn)椋孩贊駸嶂形⑸锏牡鞍纵^易凝固；②濕熱的穿透力比干熱大；③水由氣態(tài)變?yōu)橐簯B(tài)可釋放潛熱，能迅速提高被滅菌物體的溫度。多數(shù)無芽胞細(xì)菌對濕熱敏感，55～60℃作用30～60min后死亡，80℃作用5～10min可殺死所有細(xì)菌的繁殖體和真菌。細(xì)菌的芽胞對高溫抵抗力強(qiáng)，例如炭疽芽胞桿菌的芽胞，可耐受煮沸5～10min，肉毒梭菌芽胞則需煮沸3～5h才死亡。
（1）干熱滅菌法
干熱（dry heat）的殺菌作用是利用火焰，熱空氣及電磁波產(chǎn)熱等方法，使微生物脫水，干燥，細(xì)胞內(nèi)化學(xué)成分氧化和大分子變性而達(dá)到滅菌目的。
1．焚燒和燒灼（incineration and flaming）是1種徹底的滅菌方法。廢棄的物品或有感染性的動物尸體等可以直接點(diǎn)燃或在焚燒爐內(nèi)焚燒。微生物學(xué)實(shí)驗(yàn)室用的接種環(huán)，試管口，瓶口等的滅菌用燒灼方法。
2．干烤(hot air sterilization)利用干烤箱滅菌，一般加熱至160～170℃經(jīng)2h。適用于高溫下不變質(zhì)，不損壞，不蒸發(fā)的物品，例如玻璃器皿，瓷器，玻璃注射器等的滅菌。
3．紅外線(infrared)紅外線是1種波長為0.77～1000μm的電磁波，波長在1～10μm時(shí)的熱效應(yīng)最強(qiáng)。紅外線的殺菌作用與干熱相似，利用紅外線烤箱滅菌所需的溫度和時(shí)間亦同于干烤。由于熱效應(yīng)只能在照射到的表面產(chǎn)生，因此不能使物體均勻加熱。此法多用于醫(yī)療器械的滅菌。
（2）濕熱滅菌法
1．巴氏消毒法（pasteurization）用較低溫度殺滅液體中的病原菌，如結(jié)核分枝桿菌，布魯菌，而仍保持物品中所需的不耐熱成分不被破壞的消毒方法。此法由巴斯德創(chuàng)立。方法是加熱至61.1～62.8℃ 30min或71.7℃加熱15～30s，目前多采用后者。主要用于牛乳的消毒。
2．煮沸法（boiling water）在1個大氣壓下，水的煮沸溫度為100℃，5min可殺死一切細(xì)菌繁殖體，而細(xì)菌的芽胞則需1～2h，對個別細(xì)菌的芽胞則需5h才能殺死。若在水中加2%的碳酸鈉，可提高沸點(diǎn)溫度達(dá)105℃，不僅可縮短煮沸時(shí)間，還可防止金屬器皿生銹。煮沸法可用于餐具，金屬器皿的消毒，時(shí)間至少應(yīng)在10min以上。煮沸法不適合在高海拔地區(qū)使用。
3．流動蒸氣法(free-flowing steam)又稱常壓蒸汽消毒法，在1個大氣壓下，利用水煮沸時(shí)產(chǎn)生的水蒸汽進(jìn)行消毒。細(xì)菌繁殖體經(jīng)100℃15～30min被殺死，但不易殺死芽胞。該法常用的器具是Arnold消毒器，我國的蒸籠具有相同的原理?？捎糜谝话阃饪破餍?，注射器，食具和一些不耐高熱物品的消毒。
5．間歇蒸氣滅菌法（fractional sterilization）利用反復(fù)多次的流動蒸汽間歇加熱,以達(dá)到滅菌的目的。方法是將需要滅菌的物品放Arnold滅菌器或蒸籠中，經(jīng)100℃15～30min，殺死其中的繁殖體，取出后放37℃孵箱過夜，使殘存的芽胞發(fā)育成繁殖體，次日再蒸1次，如此連續(xù)3次以上，可達(dá)到滅菌的效果。此法適用于一些不耐高熱的含糖，牛奶等培養(yǎng)基。
5．高壓蒸氣滅菌法（autoclaving steralization）是1種最有效，最常用的滅菌方法。其原理是用密閉滅菌器使壓力上升至103.4kPa或1.05kg/cm2，水的沸點(diǎn)達(dá)到121.3℃，保持15～20min，即可殺死包括細(xì)菌芽胞在內(nèi)所有微生物。常用于細(xì)菌培養(yǎng)基，玻璃器皿，生理鹽水，手術(shù)敷料等耐高溫，耐濕物品的滅菌。2，輻射殺菌法
（1）紫外線（ultraviolet radiation,UV）
紫外線的波長為10～400nm，波長在240～280nm的紫外線（包括日光中的紫外線）均具有殺菌作用，其中以265～266nm殺菌作用最強(qiáng)，這與DNA的吸收光譜范圍1致。紫外線的殺菌機(jī)理是作用于DNA，使1條DNA鏈上相鄰兩個胸腺嘧啶共價(jià)結(jié)合而形成2聚體，干擾DNA的轉(zhuǎn)錄復(fù)制，進(jìn)而影響蛋白質(zhì)合成而引起微生物死亡。紫外線穿透力較弱，普通玻璃，紙張，塵埃，水蒸汽等均能阻擋紫外線。因適用于空氣，物體表面的消毒滅菌，如無菌室，手術(shù)室，燒傷病房，傳染病房，細(xì)胞培養(yǎng)室的空氣消毒及不耐熱物品的表面消毒。殺菌波長的紫外線對人體皮膚，眼睛有損傷作用，并可誘發(fā)皮膚癌，應(yīng)注意防護(hù)。
（2）電離輻射（ionizing radiation）
電離輻射具有較高的能量和較強(qiáng)的穿透力，包括X射線，γ射線和高速電子等。在足夠劑量時(shí)，對各種細(xì)菌均有致死作用。其機(jī)制在于電離輻射可在瞬間產(chǎn)生大量的自由基，能破壞DNA，損傷細(xì)胞膜。電離輻射常用于大量1次性醫(yī)用塑料制品，生物制品的消毒，亦可用于食品的消毒，而不破壞其營養(yǎng)成分。
（3）微波（microwave）
微波是1種波長為1mm～1m的超高頻電磁波，其機(jī)理是利用高頻電場產(chǎn)生高頻電磁場造成分子劇烈運(yùn)動而產(chǎn)生熱量，使微生物蛋白質(zhì)變性凝固。微波可穿透玻璃，塑料薄膜與陶瓷等物質(zhì)，但不能穿透金屬表面，多用于檢驗(yàn)室用品，食品食具，藥杯等用品的消毒。常用微波爐有2450MHz和915MHz兩種。微波對人體有害，應(yīng)減少接近工作中微波爐的次數(shù)。
3，濾過除菌法
濾過除菌法（filtration）是用物理阻留的方法去除液體或空氣中的細(xì)菌，以達(dá)到無菌目的。所用的器具是濾菌器（filter），濾菌器有許多微細(xì)的小孔，只允許液體或氣體通過，而大于孔徑的細(xì)菌等顆粒則被阻隔在篩板或?yàn)V膜的上面。該方法主要用于不耐熱的血清，毒素，抗生素，細(xì)胞培養(yǎng)液的除菌以及超凈工作臺中空氣的濾過除菌。目前常用的有以下四種濾菌器。
1．玻璃濾菌器(glass filter)在玻璃漏斗嵌入玻璃砂篩板制成，分G1-G66個型，G1-G4孔徑大，用于濾清液體，G5和G6用于除菌。G6除菌較G5徹底，但支原體和L型細(xì)菌仍有通過的可能，使用時(shí)應(yīng)予注意。
2．石棉濾菌器（asbestos filter）亦稱Seitz濾菌器。由3部分組成，上部為金屬圓筒，下部為金屬托盤及漏斗，上部的金屬圓筒用以盛裝需要過濾除菌的液體，下部的金屬托盤及漏斗用以接受濾出的液體，上下兩部分中間放石棉濾板，按石棉濾板孔徑大小分為K，EK和EK-S3種。K型濾孔最大，供澄清液體用；EK濾孔較小，供濾過除菌；EK-S濾孔更小，可阻止1部分較大的病毒通過。
3．薄膜濾菌器(membrane filter)是將不同孔徑的硝化纖維素薄膜固定在相應(yīng)濾器的下部。薄膜濾器有不同容量及不同孔徑規(guī)格，其中以微量針頭濾器在實(shí)驗(yàn)室較常用，主要用于小劑量液體的除菌。
4．高效空氣顆粒濾菌器(high efficiency particulate air filter, HEPA filter)為大型濾器，是應(yīng)用空氣壓縮機(jī)產(chǎn)生1定壓力的空氣氣流，通過1定孔徑的濾板以除去空氣中小于0.3μm的顆粒。如醫(yī)院的手術(shù)室，燒傷病房，無菌制劑室及超凈工作臺等的除菌。
四，超聲波殺菌法
超聲波（ultrasonic vibration）20kHz～100kHz的高頻聲波對病原微生物具有1定的殺滅作用。其機(jī)制主要是高頻聲波通過液體時(shí)，在應(yīng)力薄弱區(qū)產(chǎn)生許多直徑在10μm的小空腔，小空腔逐漸增大，最后爆裂而產(chǎn)生巨大壓力，爆裂時(shí)的壓力可達(dá)到1000個大氣壓，能破壞病原微生物的結(jié)構(gòu)而引起微生物死亡。超聲波殺滅病原微生物不徹底，但能明顯減少病原微生物的數(shù)量，可用于餐具消毒。目前主要應(yīng)用超聲波粉碎細(xì)胞，以提取細(xì)胞組分或制備抗原等。
五，其他物理抑菌或殺菌方法
低溫，高滲和干燥也具有1定的抑菌或殺菌作用。
（1）低溫(low temperature)
低溫可減低病原微生物的新陳代謝，抑制其生長繁殖。不但不能殺死病原微生物，還有利于病原微生物的長期存活，故常利用低溫保存病原微生物。利用低溫貯藏食物和藥品不容易發(fā)生變質(zhì)。利用低溫反復(fù)多次的凍融可明顯減少細(xì)菌的數(shù)量，因而有1定的消毒滅菌作用。因?yàn)閮鰰r(shí)細(xì)菌內(nèi)部水分形成結(jié)晶，能損傷細(xì)胞結(jié)構(gòu)，破壞細(xì)胞內(nèi)膠質(zhì)狀態(tài)，并可產(chǎn)生膨脹，導(dǎo)致細(xì)菌崩解。實(shí)驗(yàn)室常用此原理制備細(xì)菌的可溶性抗原。
（2）干燥（desiccation）
干燥可使病原微生物脫水，濃縮，新陳代謝減慢，甚至引起死亡。不同病原體對干燥環(huán)境的耐受性不同，如腦膜炎奈瑟菌，淋病奈瑟菌，蒼白密螺旋體和流感病毒等對干燥敏感，而結(jié)核分枝桿菌，溶血性鏈球菌，炭疽芽胞桿菌以及真菌，乙型肝炎病毒等對干燥有1定抵抗力。干燥法主要用于保存食物，防止食物變質(zhì)。
（3）冷凍真空干燥法（lyophilization）
冷凍真空干燥法是在低溫狀態(tài)下真空抽去菌體內(nèi)的水分，既可以使病原微生物脫水，新陳代謝減緩，又可避免冷凍時(shí)菌體內(nèi)水分結(jié)晶對細(xì)菌的損傷。是目前保存菌種的好方法，一般可保存微生物數(shù)年至數(shù)十年。
Disinfection and sterilization and biological safety
Microbes are easily affected by external conditions. If the environment is suitable, it can promote the growth and reproduction of microbes, and severe environmental changes can inhibit the growth of microbes and even die. As microorganisms exist widely in nature and some of them are pathogenic microbes, medical workers and related researchers must firmly establish aseptic concepts and strictly enforce aseptic operations from the perspective of preventing infection and avoiding laboratory microbial contamination. For example, medical devices, operation room and asepsis room should be properly disinfected or sterilized. In order to prevent the spread of disease, the excrement of infectious disease patients and laboratory waste culture should also be disinfected or sterilized. Sterilization and disinfection are very important basic operation techniques in clinical medicine and microbiology. Different methods are used and the effects are different. The following are the commonly used terms for disinfection and sterilization.
1. disinfection (disinfection) means the method of killing pathogenic microorganisms on or in the environment, but it does not necessarily kill bacterial spore or non pathogenic microbes, such as the disinfection of drinking water. The chemicals used for disinfection are called disinfectants (disinfectant).
2. sterilization (sterilization) means the method of killing or removing all microorganisms on an object, including all pathogenic microbes and non pathogenic microbes and bacterial spore. For example, normal saline for injection, surgical dressing and culture medium are needed after sterilization. It is generally preferred to sterilize the physical method.
3. antisepsis is the way to prevent or inhibit the growth and reproduction of bacteria in vitro. Bacteria usually do not die. For example, adding 0.01% of Salix in biological preparations can prevent the growth of heterozygous bacteria. The same chemicals are disinfectants at high concentrations, and can be used as preservatives at low concentrations. Antibiotics that inhibit the growth and reproduction of bacteria are called bacteriostasis, and these antibiotics are called bacteriostat. In vivo inhibition of bacterial multiplication can be used in vitro for bacteriostatic test to detect the sensitivity of bacteria to antibiotics.
4. asepsis (asepsis) and aseptic operation (aseptic technique) asepsis means no live microorganisms, for the result of sterilization. The operation technology to prevent microorganisms from entering the body or contaminant is called aseptic operation. If bacteria need to be prevented from entering the wound during surgery, microbiological laboratory operations should pay attention to the prevention of microbial contamination and infection.
First section of physical sterilization and sterilization
Disinfection and sterilization methods are generally divided into two categories: physical and chemical methods. The main physical factors for disinfection and sterilization are heat, radiation, filtration, sterilization, ultrasonic, low temperature and drying.
1. Thermal sterilization
High temperature has obvious lethal effect on microorganism, which is mainly used for disinfection and sterilization by denaturing protein, destroying cell membrane and degrading nucleic acid. Thermal sterilization is divided into two major categories: dry heat sterilization and damp heat sterilization. At the same temperature, the effect of moisture and heat sterilization is better than dry heat sterilization. This is because: (1) the protein of microorganism is easier to solidify in damp heat; (2) the penetrating force of damp heat is larger than dry heat; (3) water from gaseous to liquid can release latent heat and can quickly raise the sterilized object. Temperature. Most of the non-spore bacteria were sensitive to humidity and heat. They died after 30-60 minutes at 55-60 C, and all the propagules and fungi could be killed after 5-10 minutes at 80 C. Bacterial spores are highly resistant to high temperature, such as Bacillus anthracis, which can endure boiling for 5 to 10 minutes, and Clostridium botulinum spores need boiling for 3 to 5 hours before they die.
(1) dry heat sterilization
The bactericidal effect of dry heat (dry heat) is to use the method of flame, hot air and electromagnetic wave to produce heat, so as to dehydrate and dry the microorganism, to oxidize the chemical components in the cell and to be denatured by the macromolecule.
1. burning and cautery (incineration and flaming) is a thorough sterilization. Discarded articles or infected animal carcasses can be ignited directly or incinerated in an incinerator. Cauterization methods for sterilizing rings, test tubes and bottle mouths in microbiology laboratory.
2. dry bake (hot air sterilization) is sterilized in a dry oven, generally heated to 160~170 degrees centigrade by 2 h. It is suitable for sterilization of non-deteriorating, non-destructive and non-evaporative articles at high temperatures, such as glassware, porcelain, glass syringes, etc.
3. Infrared (infrared) infrared is a kind of electromagnetic wave with wavelengths of 0.77-1000 micron. The thermal effect is strongest when the wavelengths are 1-10 micron. The bactericidal effect of infrared rays is similar to that of dry heat. The temperature and time required for sterilization by infrared oven is also similar to that of dry roasting. Since the thermal effect can only be generated on the surface of the irradiated surface, it can not uniformly heat the object. This method is used for sterilization of medical instruments.
(two) wet heat sterilization
1. pasteurization disinfection method (pasteurized disinfection method) uses lower temperature to kill pathogenic bacteria in liquid, such as Mycobacterium tuberculosis and Brucella, and still maintain the disinfection method that the heat resistant components are not destroyed. This law was founded by Pasteur. The method is to heat up to 61.1 to 62.8 30min or 71.7 to 15 to 30s. It is mainly used for sterilizing milk.
2. boiling method (boiling water) at 1 atmospheric pressure, the boiling temperature of water is 100 degrees C, 5min can kill all the bacterial propagating body, and the bacterial bud is 1~2 h, and the bud of individual bacteria is 5 h to kill. If 2% sodium carbonate is added to the water, the boiling point temperature can be raised to 105 C, which can not only shorten the boiling time, but also prevent the metal vessels from rusting. The boiling method can be used for disinfection of tableware and metal utensils, and the time should be at least 10min. The boiling method is not suitable for use in high altitude areas.
3. Free-flowing steam, also known as atmospheric steam sterilization, is used to sterilize water vapor produced by boiling water at an atmospheric pressure. The bacterial propagule was killed at 100 C 15~30 min, but it was not easy to kill spores. The common appliance of this method is Arnold sterilizer, and the steamer in our country has the same principle. It can be used for sterilizing general surgical instruments, syringes, food utensils and some non high heat resistant items.
5. Fractional sterilization uses intermittent heating of repeatedly flowing steam to achieve the purpose of sterilization. The method is to put the sterilized items in the Arnold sterilizer or steamer to kill the reproductive body after 100 C 15 ~ 30min and take out the incubator at 37 degrees C for the night after taking out the incubator to make the remaining bud develop into a reproduction body, and then steamed again the next day, so that the sterile fruit can be achieved. This method can be applied to some medium which contains high sugar and milk.
5. high pressure steam sterilization (autoclaving steralization) is one of the most effective and commonly used sterilization methods. The principle is to use a closed sterilizer to increase the pressure to 103.4kPa or 1.05kg/cm 2. The boiling point of water reaches 121.3 degrees C and 15 ~ 20min can be maintained to kill all microbes, including bacterial spore. It is often used for sterilization of high temperature and humidity resistant substances, such as bacterial culture medium, glassware, physiological saline, surgical dressing, etc.
Two. Radiation sterilization
(1) ultraviolet (ultraviolet radiation, UV)
UV wavelengths are 10 to 400nm, and ultraviolet (including ultraviolet rays in sunlight) of 240 ~ 280nm have bactericidal effect. The bactericidal effect of 265 ~ 266nm is the strongest, which is in accordance with the absorption spectrum of DNA. The bactericidal mechanism of ultraviolet radiation is DNA, which covalently combines two adjacent thymine on a DNA chain to form a two polymer, which interferes with the transcriptional replication of DNA and then affects the protein synthesis and causes the microbial death. UV light penetration is weak, ordinary glass, paper, dust, water vapor and so on can block UV. It is suitable for disinfection and sterilization of air and surface, such as asepsis room, operation room, burn ward, infection ward, cell culture room air disinfection and surface disinfection of heat resistant articles. Ultraviolet rays at sterilization wavelength can damage human skin and eyes, and can induce skin cancer.
(two) ionizing radiation (ionizing radiation)
Ionizing radiation has high energy and strong penetrating power, including X rays, gamma rays and high speed electrons. At sufficient doses, they are lethal to all kinds of bacteria. The mechanism is that ionizing radiation can produce large amounts of free radicals in an instant, destroy DNA and damage cell membrane. Ionizing radiation is often used to disinfect a large number of disposable medical plastic products and biological products. It can also be used to disinfect food without destroying its nutrients.
(three) microwave (microwave)
Microwave is a kind of ultra high frequency electromagnetic wave with wavelengths of 1mm to 1m. The mechanism is that high frequency electric field is used to produce high frequency electromagnetic field, which causes intense molecular motion to produce heat, which makes microorganism protein denatured and solidified. Microwave can penetrate glass, plastic film and ceramics, but it can not penetrate the surface of metal, and it can be used for disinfection of laboratory articles, food utensils, medicine cups and other articles. 2 450MHz and 915MHz two kinds of microwave ovens are used in common use. Microwave is harmful to human body. It should reduce the number of microwave oven approaching to work.
Three, filtrating bacteria removing method
Filtering is a method of removing bacteria from liquid or air by physical retention to achieve sterility. The apparatus used is filter. The filter has a number of tiny holes, which only allow liquid or gas to pass through, and the particles, which are larger than the aperture, are blocked on the top of the sieve plate or filter membrane. This method is mainly used for sterilization of heat-resistant serum, toxin, antibiotics, cell culture medium and filtration of air in super-clean worktable. There are four kinds of bacteria filters commonly used at present.
The 1. glass filter (glass filter) is made of glass funnel embedded in glass sand sieve plate, divided into G 1 -G 66 types, G 1 -G 4 aperture large, used for filtrating liquid, G 5 and G 6 for degrading bacteria. G 6 is more thorough than G 5, but mycoplasma and L type bacteria still have the possibility of passing.
2. asbestos filter (asbestos filter) is also known as Seitz filter. It is composed of three parts, the upper part is the metal cylinder, the lower is the metal tray and the funnel, the metal cylinder in the upper part is used to fill the liquid which needs to filter the bacteria, the lower metal tray and the funnel are used for the filtrated liquid, and the upper and lower two parts of the asbestos filter plate are placed in 3 kinds according to the pore size of the asbestos filter plate, K, EK and EK-S. The K-type filter is the largest for clarifying liquids; the EK filter is smaller for filtering and sterilization; and the EK-S filter is smaller for preventing the passage of larger viruses.
3. membrane filter filters the nitrocellulose film with different apertures at the bottom of the filter. Membrane filters have different capacities and different aperture specifications, of which microneedle filters are commonly used in laboratories, mainly for the sterilization of small doses of liquid.
4. the high efficiency air particle filter (high efficiency particulate air filter, HEPA filter) is a large filter, which uses air compressor to produce a certain pressure air flow, through a certain aperture of the filter plate to remove the particles less than 0.3 mu in the air. Such as hospital operation room, burn ward, sterile preparation room and ultra clean workbench sterilization.
Four. Ultrasonic sterilization
The high frequency sound wave (ultrasonic vibration) 20kHz ~ 100kHz has certain killing effect on pathogenic microorganisms. The mechanism is that when the high frequency sound waves pass through the liquid, many small cavity with 10 m diameter are produced in the weak stress area. The small cavity increases gradually, and the pressure can be burst at the end. The pressure of the burst can reach 1000 atmospheric pressure, which can destroy the structure of the pathogenic microorganism and lead to the death of the microorganism. Ultrasound can kill the pathogenic microorganism thoroughly, but it can obviously reduce the number of pathogenic microorganisms, and can be used for tableware disinfection. At present, ultrasound is used to crush cells to extract cell components or prepare antigens.
Five. Other methods of physical bacteriostasis or bacteriostasis
Low temperature, high permeability and drying also have certain bacteriostatic or bactericidal effects.
(1) low temperature (low temperature)
Hypothermia can reduce the metabolism of pathogenic microorganisms and inhibit their growth and reproduction. Not only can not kill pathogenic microorganisms, but also conducive to the long-term survival of pathogenic microorganisms, so the use of cryopreservation of pathogenic microorganisms. Food and medicines stored at low temperatures are not likely to deteriorate. Repeated freezing and thawing at low temperature can significantly reduce the number of bacteria and thus have certain disinfection and sterilization effects. Because the water inside the bacteria forms crystals during freezing, it can damage the cell structure, destroy the glial state of the cells, and produce expansion, leading to bacterial disintegration. This principle is used to prepare soluble antigens of bacteria.
(two) drying (desiccation)
Drying can cause pathogenic microorganisms to dehydrate, concentrate, slow down metabolism, or even cause death. Different pathogens have different tolerance to dry environment, such as Neisseria meningitidis, Neisseria gonorrhoeae, pallid Treponema, and influenza virus, while Mycobacterium tuberculosis, hemolytic streptococcus, Bacillus anthracis, fungi, hepatitis B virus and so on have certain resistance to drying. The drying method is mainly used to preserve food and prevent food deterioration.
(three) freeze vacuum drying (lyophilization)
The freezing vacuum drying method is used to remove the moisture in the bacteria under the condition of low temperature. It can not only dehydrate the pathogenic microorganism and slow down the metabolism, but also avoid the damage of the water crystallization of the bacteria to the bacteria during the freezing. It is the best way to preserve bacteria at present. It can preserve microorganisms for several decades to decades.