1、 Before sampling: Clarify requirements and make basic preparations

The planning before sampling is a prerequisite for ensuring effectiveness, and a targeted plan should be developed based on the testing objectives (such as environmental monitoring, disinfection effect evaluation, scientific research analysis, etc.).

1. Reasonably choose the type of sampler

Samplers with different principles are suitable for different scenarios and microbial characteristics, and selecting the matching type is the basis:

Impact samplers (such as Anderson cascade impact samplers and crevice impact samplers): By using high-speed airflow to impact microorganisms onto culture media or capture membranes, they are suitable for detecting live bacteria that need to be cultured (such as total bacterial count determination), especially for capturing microorganisms of different particle sizes (cascade impact can distinguish aerosol particle size distribution).

Filter sampler (such as membrane filter sampler): using filter membranes (such as polycarbonate membrane, mixed cellulose membrane) to intercept microorganisms, suitable for high-sensitivity detection (such as qPCR quantification, virus detection), or scenarios that require simultaneous analysis of the association between microorganisms and particulate matter, but attention should be paid to the influence of filter membrane material on microbial activity (such as selecting low adsorption filter membranes).

Settling sampler (such as plate settling method): simple to operate but low efficiency, only suitable for rough environmental microbial screening (such as daily monitoring in clean rooms), not recommended for low concentration or small particle size microbial sampling.

Centrifugal sampler: It separates microorganisms through centrifugal force and is suitable for sampling in flowing scenes (such as workshops and public places). Its advantages are small size and portability, but the capture efficiency is greatly affected by the stability of the airflow.

2. Optimize the selection of capture media

The capture medium (culture medium, filter membrane, absorption solution) directly determines the capture efficiency and survival ability of microorganisms:

Selection of culture medium: Select specialized culture medium based on the characteristics of the target microorganisms (such as nutrient agar for detecting bacteria, potato glucose agar PDA for fungi, and selective culture medium for pathogenic bacteria); Ensure that the culture medium is fresh (refrigerated at 4 ° C for no more than 7 days after preparation), with a uniform thickness (approximately 3-5mm), and avoid drying or contamination.

Filter membrane selection: Priority should be given to low adsorption and high porosity filter membranes (such as polytetrafluoroethylene PTFE membranes, nitrocellulose membranes) to reduce microbial losses caused by static electricity or adsorption; The pore size of the filter membrane should match the size of the microorganisms (usually 0.22 μ m or 0.45 μ m, and 0.1 μ m filter membrane can be used for virus sampling).

Absorption liquid selection: When used for liquid absorption samplers, the absorption liquid should balance "capture efficiency" and "microbial activity preservation" (such as using physiological saline or buffer containing 0.05% -0.1% Tween 80 to reduce microbial sedimentation and adsorption; virus sampling can add bovine serum albumin (BSA) to protect the virus structure).

3. Avoid contamination before sampling

Microbial sampling is susceptible to external contamination and requires strict control of the "sterile environment" prior to sampling

Samplers (such as the nozzle, filter membrane clamp, and sampling tube of impact samplers) need to be sterilized in advance (high-pressure steam sterilization at 121 ℃/20 min, or dry heat sterilization at 160 ℃/2 h; plastic parts can be wiped with 75% alcohol and sterilized by UV for 30 min).

The capture media such as culture medium and filter membrane should be loaded under sterile conditions (such as operating in an ultra clean workbench) to avoid hand contact or air exposure contamination.

Pre balance the sampling area before sampling (such as closing doors and windows for 30 minutes before sampling in a clean room to avoid airflow disturbance caused by personnel movement).

2、 Sampling: Optimizing parameter settings and operating standards

The parameter control and operational details during the sampling process are the core of improving capture efficiency, and need to be dynamically adjusted according to the sampler principle and environmental conditions.

Optimize core sampling parameters

Adjust key parameters to maximize capture efficiency based on sampler type and detection requirements:

Sampling flow rate: The flow rate should match the design of the sampler (e.g. Anderson sampler recommends a flow rate of 28.3L/min, while crack sampler can be set at 10-30L/min). Low flow rate can lead to insufficient capture of small particle size microorganisms (<5 μ m); If the flow rate is too high, it may cause microbial inactivation or splashing of the culture medium due to airflow impact. It is recommended to calibrate the flow rate using a "flow calibrator" before sampling (with an error controlled within ± 5%).

Sampling time: It is necessary to balance the "capture amount" and "microbial activity". Short term sampling (5-15 minutes) is suitable for high concentration environments (such as polluted workshops) to avoid excessive wetting of the culture medium or excessive accumulation of microorganisms; Long term sampling (30-60 minutes) is suitable for low concentration environments (such as clean rooms and operating rooms), but it should be noted that the sampling time of the impact sampler should not exceed 60 minutes (to avoid drying the culture medium), and the filtration sampler should prevent filter membrane blockage (large particles can be removed through pre filtration).

Sampling height and position: Determine the sampling point according to the detection purpose:

Environmental monitoring: The sampling height is 1.2-1.5m (level with the human breathing zone), and 3-5 sampling points are set up in each area (evenly distributed, avoiding wall corners, ventilation openings, and directly above pollution sources).

Disinfection effect evaluation: Samples should be taken at the same location before and after disinfection to ensure consistency in comparison.

Aerosol traceability: Sampling points can be set at different heights (such as 0.5m, 1.5m, 3m) to analyze the vertical distribution of microorganisms.

Airflow stability control: During sampling, avoid the sampler directly facing the ventilation opening, fan, or direction of personnel movement; If necessary, turn off local ventilation equipment or use windproof covers to fix the sampler to reduce sampling deviation caused by airflow disturbance.