Activity of Biostatic Agents on the Microbial Colonization in Particle Filter Department of Comparative Morphology and Biochemistry, University of Camerino, Italy EKASTU Safety GmbH, Stuttgart, Germany

Introduction It is well known that atmospheric air acts as a carrier responsible for the non uniform distribution of the airborne microbial cells and/or sporal forms, the concentration of which is subject to strong variations according to the habitat to man. The need to control the particulate has lead to new attention towards the media types and techniques for the filtration and depollution of the air especially where the absence of polluting particles and micro organisms are required. Recent researches have demonstrated that some micro organisms, particularly certain fungi, are capable of colonizing substrates in situ. The efficacy of particle filters in retaining particles, including micro organisms, has been well studied and other studies prove that filter matrix can represent a feeding source for bacteria and fungi and it can become a colonization site. Moreover, the organic/inorganic material settled on the panel after air filtration contributes to the microbial growth, that inevitably leads to a loss of filter efficacy and to a probable filter deterioration (bio oration) with the eventual release of micro organisms, both vegetative and spiral forms and the probable emission of Volatile Organic Compounds (VOCs) produced by the microbial metabolism on the downstream site. The aim of this study study was to verify the real microbial colonization of test strains on microfiber glass-acrylic filter media, both before and after a significant utilization time. We then tested some antimicrobial agents added to the filters, which are able to reduce the microbial colonization, in order to preserve the efficiency, so excluding them as potential risk agents for the air quality.

Studied Filters Untreated Filter Filter used new BIOSTOP Filter Microbial Growth on Filter 50  l of each test microbial strain spread on the sections (  9 mm). Incubation at 25°C, humidity of 90% Filter Integrity Verification -Sections (  48 mm ) spread with 50  l of a mixed culture. Incubation at 25°C, humidity of 90% -20 l/min air flow aspiration for 5 min through used sections and count of released colonies Materials and Methods

Microbial Growth on Filter Samples  Untreated  Untreated filters showed a growth of microbial strains both in new filters and more abundantly, in used ones. BIOSTOP Filters Filters treated treated with antimicrobial gave only a slight evidence of fungal colonization.

Untreated Filter BIOSTOP Filter Release Curves of Bacteria and Fungi from BIOSTOP and Untreated Filter at Different Incubation Times Bacteria + Fungi  Untreated filters BIOSTOP Filterstreated  Untreated filters showed a growth of microbial strains both in new filters and, more abundantly, in used ones. BIOSTOP Filters treated antimicrobial gave only a slight evidence of fungal colonization.

Test Micro Organisms Yielded on Filter Sections BIOSTOP Filter used new Untreated Filter

Bioporation Testing Apparatus 20 l/min air flow BIOSTOP Filter after 27 Days of Incubation Untreated Filter after 27 Days of Incubation

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