Mikrobiologische Bewertung technischer Wassersysteme in Abluftreinigungsanlagen von Schweinemastbetrieben/Microbiological assessment of technical water systems in exhaust air purification systems at pig farms

Air purification systems in pig-fattening farms provide favorable conditions for the growth of potentially pathogenic microorganisms such as Legionella pneumophila, due to moderate temperatures, high nutrient availability, and water stagnation. Previous studies have already shown that both the process water and the emitted clean air can pose a health risk. The drinking water used to supply these systems has been suspected as a potential source of Legionella contamination; however, comprehensive investigations have so far been lacking. This study addresses this gap, with a particular focus on emergency showers that would be fed from the same water source. If not flushed regularly, the emergency showers may contribute not only to the introduction of Legionella into the air purification systems but also pose a direct occupational health risk: the release of Legionella-containing aerosols during use. In two pig-fattening farms, freshwater and shower samples were analyzed using immunomagnetic separation combined with flow cytometry (IMS-FCM) and a so-called standard addition quantitative PCR (SA-qPCR). Legionella – including viable L. pneumophila – was detected in all samples, with partly significantly higher concentrations found in emergency showers compared to the corresponding freshwater. These results point to a previously underestimated health hazard for farm personnel and provide indications of possible sources for the presence of Legionella in the clean air of the air purification systems. As a relevant occupational safety measure, it is recommended documented in order to effectively minimize Legionella exposure during daily operations. On-site analysis using IMS-FCM proved to be an effective tool for rapid microbiological assessment to identify sources of health hazards in unparalleled response time.