Commonly used sterilization and disinfection methods and effect monitoring in microbiological experiments

Since microorganisms are widely present in the environment, from the perspective of preventing cross-contamination, microbiological experiments must follow the principle of aseptic operation and adopt a variety of physical, chemical or biological methods to ensure that all items and working environments meet the requirements of use
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Disinfection: Killing or (and) removing pathogenic microorganisms so that their numbers are reduced to the point that they no longer cause illness in humans
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Sterilization: All microorganisms are killed or (and) removed, including bacterial spores and non-pathogenic microorganisms
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Sterility: It does not contain live bacteria and is the result of sterilization
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(1) Commonly used methods of sterilization and disinfection

Commonly used sterilization or disinfection methods are divided into 4 categories: heat sterilization, chemical sterilization, radiation and filtration sterilization
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1.
Heat Sterilization High temperature has obvious killing effect on microorganisms, which is due to heat energy changing proteins, nucleic acids and destroying cell membranes
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Table 4-4 Types and scope of heat sterilization

2.

Table 4-5 Chemical disinfectants and their scope of use

3.

4.
Filtration sterilization method refers to passing bacteria-containing liquid or gas through a device called a bacterial filter, so that the bacteria are subjected to mechanical resistance and stay on the filter or filter plate, so as to achieve the purpose of sterilization
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This method is often used for liquid substances that are not suitable for heat sterilization, such as medium additives, antibiotics, and serum
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Its biggest advantage is that it does not destroy the chemical composition of various substances in the liquid, but viruses and mycoplasma that are smaller than bacteria cannot be removed
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The ultra-clean workbench is also designed according to the principle of filtration sterilization
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(2) Effect monitoring

The laboratory must regularly monitor the effects of disinfection and sterilization
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1.
Monitoring the effect of high-pressure steam sterilization High-pressure steam sterilization should be subject to process monitoring, chemical monitoring and biological monitoring
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Process monitoring should be carried out for each pot and recorded in detail
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Chemical monitoring should be carried out in each package, and 3M sterilization indicator tape is commonly used
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This tape is printed with a diagonal white indicating line pattern, which is attached to the surface of the object to be sterilized.
After 20 minutes at 121°C, the tape changes color 100% (the stripe pattern becomes a black diagonal strip)
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Biological monitoring should be carried out monthly.
The new sterilizer must be subjected to biological monitoring before it is used, and it can be used only after it is qualified
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Biological indicators include spore suspension, spore flakes, and indicator tubes in which the flakes and culture medium are mixed
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After sterilization, take out the biological indicator and inoculate it in bromocresol purple glucose peptone water medium, and place it in a 55～60℃ incubator for 2～7 days.
If the color does not change after cultivation, it is clear and transparent, indicating that the spores have been killed.
It meets the sterilization requirements
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2.
Ultraviolet disinfection effect monitoring Ultraviolet disinfection should carry out lamp irradiation intensity monitoring and biological monitoring
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The lamp irradiation intensity is monitored once every six months, and the irradiance value of 30W should not be lower than 70μW/cm2
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Newly used lamps should also be monitored, not less than 100μW/cm2
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Biological monitoring should be carried out when necessary, and it is required that the disinfected items or natural bacteria in the air should be reduced by more than 90%, and the killing rate of artificial bacteria should reach 99.
9%
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3.
Environmental monitoring Environmental monitoring includes monitoring of air, instruments and equipment, surface of objects and staff hands
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Environmental monitoring should be conducted when laboratory contamination is suspected
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4.
The monitoring of disinfection and sterilization items should be random random inspections of disinfection and sterilization items regularly.
Disinfection items must not be detected with pathogenic microorganisms, and sterilization items must not be detected with any microorganisms
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