SOP FOR PASSIVE AIR SAMPLING (SETTLE PLATE METHOD) FOR VIABLE COUNT SECTION OF THE MICROBIOLOGICAL LABORATORY

Objective:

To collect viable microorganisms from the air and determine their concentration using the settle plate method.

Materials:

• Sterile Petri dishes with appropriate growth media
• Sterile forceps
• Clock or timer
• Incubator set to 35°C
• Marker pen
• Alcohol wipes
• Gloves
• Lab coat
• Hairnet
• Safety glasses

Procedure:

1. Prepare the media plates by pre-incubating them at 32oC±2.5oC for 24-48 hours.
2. Label the media plates with the location name, date of exposure, observation date, and plate number.
3. Wrap the media plates in aluminum foil and place them in a stainless steel closed container.
4. Transfer the container under the UV light of the pass-through window for at least 2 hours.
5. Move the container to the sterile area and ensure proper airflow.
6. Expose two media plates for each single location for at least 2.5-4 hours.
7. Put the lids back on the media plates and collect them from each location.
8. Repack the media plates in aluminum foil and place them in the stainless steel container.
9. Transfer the container back to the pass-through window.
10. Move the media plates to the incubation room of the microbiology lab.
11. Incubate the media plates at 22oC±2.5oC for 3-5 days for yeast and mold count.
12. Incubate the media plates at 32oC±2.5oC for 2-3 days for bacterial count.
13. After incubation, observe the media plates and count the number of colony-forming units.
14. Record the results in the respective reports.
15. Perform at least 3 consecutive plate exposure runs before allowing aseptic injection filling.
16. The average result of these three runs will decide whether the area is ready for aseptic filling activity or not.

Safety Precautions:

• Always wear gloves, lab coat, hairnet, and safety glasses when working in the microbiological lab.
• Handle the Petri dishes aseptically to prevent contamination.
• Discard any contaminated petri dishes.
• Clean and disinfect the work surface after use.

Interpretation of Results:

The results of the passive air sampling can be used to assess the microbiological quality of the air in a given area. A high concentration of viable microorganisms may indicate a potential contamination problem. However, it is important to consider the sampling location and the time of day when interpreting the results. For example, the concentration of viable microorganisms may be higher in areas with high traffic or in areas where food is being prepared.

Repeatability and Reproducibility:

Passive air sampling is a repeatable and reproducible method for collecting viable microorganisms from the air. However, the results of the sampling may vary depending on the sampling location, the time of day, and the type of growth media used.

References:

• Air Sampling: Frequently Asked Questions and Best Practices: https://biosci-intl.com/best_practices_faq.htm
• Passive Air Sampling Procedure: https://safefoodalliance.com/testing-analysis/passive-air-sampling-step-by-step-guide/
• SOP for Monitoring of Microbiology Laboratory: https://www.pharmaguideline.com/2010/01/sop-for-monitoring-of-microbiology.html