Media plates are used in pharmaceutical labs to detect viable microorganisms in the air. They are placed in corners, near doors, critical work areas, and where sterilized materials are processed. Plates are positioned to capture maximum particles; large ones settle quickly due to gravity, while smaller particles take longer due to air currents. Media plates work best in still air.
After exposure, plates are incubated for two days for bacteria and up to five days for fungi and mold.
Media plates can be exposed in clean rooms for about half an hour, but experts, including EU guidelines and <1116>, recommend four hours as the optimal exposure time. This duration is based on calculations of organism settling rates. After four hours, the settling rate decreases, and the plate performs best without degradation.
Studies show that after four hours, a skin layer forms on the agar, limiting water access to microorganisms, reducing their growth, and potentially underestimating the number of viable microorganisms present. This can hinder test accuracy.
This hinders their growth, potentially leading to an inaccurate assessment of viable microorganisms, as it may appear that fewer are present than actually exist.
Media plates begin losing weight immediately upon use, reaching maximum loss after four hours, after which they should not be used further. Experiments indicate that initial weight loss is significant, then stabilizes until the four-hour mark. Beyond this, weight loss starts to negatively impact the growth of microorganisms.
The 4-hour exposure time for environmental monitoring plates is a scientifically and practically validated approach. It ensures accurate detection of airborne contaminants, aligns with regulatory requirements, and provides meaningful data for maintaining cleanroom integrity and product safety.
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Resource Person: Vikas Bedi
