Authors: Roberto Ligugnana.
The GMP Annex 1 2023 requests that microbial environmental monitoring by active and passive microbial air samplers is actuated by continuous air monitoring. A prolonged sampling produces a loss of moisture in the agar of the Petri dish and therefore it is necessary that during the “continuous time” the dryness of the nutrient media is under control to guarantee a regular growing of the cfu. The purpose of this paper is to evaluate if the agar of settle plate (which volume was reduced with a treatment under sterile laminar flow before aspiration) has still the correct nutrient characteristics during the incubation. The results of the study are summarised in Table 1 and 2.
The average loss of humidity after 4 hours in the first part of test under laminar flow was 14,7%. In the second part of test, the Petri dishes aspirated the air in a normal open environment and the average growth after incubation (indicated in cfu/ plate), in comparation with control plates with the original volume of agar, was 87%. The acceptance criteria using the US Pharmacopeia Validation Recommendation for microbiological examination (chapter ) is that the test plates had to recover < 70% of the challenge.
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