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Environmental microbial monitoring under the COVID-19

HuanKai operations teamTime: 2020/05/22

Under the COVID-19 epidemic, many people were uneasy about the virus and the mode of transmission in the environment. In particular,  the impact of air aerosols on the spread of the COVID-19 virus were reported, there were also doubts about the effect of the environment and space disinfection. At present, there are many researches on air microbial aerosol sampling, and samplers manufactured according to different principles are widely used in various fields. Such as: single-stage or multi-stage impact sampler, centrifugal sampler, cyclone sampler, liquid impulse sampler, filter sampler, etc. Among these types of samplers, the Anderson air microbial sampler has the highest sampling efficiency , The number of particles collected is larger. When collecting aerosols of different particle sizes in stages, the Anderson sampler is used frequently. Early in the year of  2010, the Institute of Pathology of the Chinese Academy of Medical Sciences conducted research on using the Anderson Air Biosampler to collect viral aerosols.

Of course, under normal circumstances, it is relatively difficult to directly sample and detect viruses in the air. However, by sampling and detecting conventional microorganisms in the air, we can reflect the cleanliness of the overall environment and thus assess our environment. The overall degree of contamination and disinfection effect.

1. Airborne bacteria:
The living microorganism particles collected in the air through the principle of natural sedimentation, through a special medium, propagated to visible colonies under suitable growth conditions. The sampling of settled bacteria belongs to passive sampling, reflecting the microorganisms carried in the dust that finally land on the ground or the surface of objects.
Detection method: The commonly used test method is the sedimentation plate method, which determines the number of microorganisms that fall from the air to the unit area of ​​the ground within a certain period of time.
Operation steps: Pour the melted nutrient agar medium or soybean casein agar medium (Sand's medium for mold monitoring) into a 90mm sterile Petri dish to make a plate (or purchase a commercial settling dish), and arrange according to the standard requirements At the monitoring point (the monitoring point is selected and laid out according to the standard), open the lid and expose it to the monitoring environment for 5 to 30 minutes (dynamic monitoring is not more than 4 hours), let the microorganisms in the air land on the surface of the plate, cover the lid, and then Put it upside down in the incubator and count the colonies after 48 hours of cultivation (SDA culture for 5 days).

                               Huankai triple - packed settlement plate

2. Air plankton
By counting the concentration method, that is, by collecting biological particles suspended in the air, through a special medium, under the appropriate growth conditions to multiply the number of visible colonies. The sampling of plankton is an active sampling, reflecting the concentration of biological particles in the air in the clean area.
Detection method: impact type plankton microbial sampler was used ommonly, which allows air to generate high-speed air flow through slits or small holes, so that microorganisms (plankton) suspended in the air are collected on a special plate medium, which is obtained after laboratory cultivation Count colonies.

2.1 Single-stage plankton sampler
Based on the Anderson impact principle (impact method), the sampling velocity of the sampling velocity is basically the same as that of the clean room. The direct sampling, airborne microorganisms are impacted on the agar surface in the culture dish through the micropores at a high speed, the impact speed is 20m / s , Equivalent to Anderson impact level 6, to ensure that particles larger than 1 micron are captured and collected.
Sampling procedure: Place the planktonic microbial sampler on the monitoring point, remove the porous sampling head and protective cover, wipe and disinfect the porous sampling head and protective cover, culture dish holder and surface with 75% alcohol, and then pre-assemble it Place the Petri dish with TSA or SDA medium (or purchase a commercial plate) on the Petri dish holder, adjust the Petri dish to the level, install the porous sampling head, set the sampling parameters, and start sampling. After sampling, open the porous sampling head, take out the Petri dish, cover the original Petri dish lid, attach a label or write a number, place it in a constant temperature incubator that has reached the set temperature, and invert the culture.

                                                       Huankai Plankton Microbial Sampler

2.2 Six-stage plankton sampler
The whole set of instrument is composed of six-stage sampling impactor, sampling control host and special tripod for six-stage sampling impactor. The six-stage sampling impactor is composed of six hard-oxidized aluminum porous impact sampling discs. Sterile plates with existing sampling media can be placed on the porous impact sampling discs. All porous impact sampling discs consist of Three spring hooks tightly connect the porous impact sampling discs. 400 precision micropores with the same aperture are arranged in a circle on the same-level porous impact sampling disc, and the apertures of different-level impact sampling discs are different. When the air containing microbial particles enters the sampling port, the gas sampling flow rate of the sampling host is constant, and when the gas passes through the sieve holes of different apertures in each sampling disc, the microbial particles of different sizes strike at different speeds according to aerodynamic characteristics On the surface of the corresponding sampling medium. The first level-the second level is similar to the particles captured by the upper respiratory tract of the human body, and the third level-the sixth level is similar to the particles captured by the lower respiratory tract. This simulates the penetration and deposition of these particles in the respiratory tract to a considerable extent.
Sampling steps:
1) Wipe and sterilize the six-stage sampling impactor with 75% alcohol (or place in an autoclave at 121 ° C for 30 minutes), and keep the impactor in a safe place.
2) Open and lock the impactor tripod, adjust the top of the tripod to the level, place the impactor on the tripod's gimbal, put the host on the table or on the ground, and connect the impactor outlet with a rubber tube → host Air inlet.
3) Put the sampling plate in the impactor in sequence, open the cover of the plate with one hand, quickly cover the sampling head (impact disk) with the other hand, then press the upper part of the impactor and hang three spring hooks. When putting in and taking out the sampling plate, you must wear a mask to prevent the mouth and nose from discharging microorganisms to contaminate the plate.
4) Turn on the power switch, set the relevant parameters, place the impactor at the monitoring point, open the upper cover of the impactor inlet, and 2 meters away from the sampling point to start sampling.
5) After the sampling is completed, release the hook spring, open the porous sampling head (impact disc) layer by layer, remove the Petri dish, replace the original Petri dish lid, attach a label or write a number, and place it at a constant temperature that has reached the set temperature In the incubator, invert the culture.

                                            Six-stage plankton sampler