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Preferential colonization and release of Legionella pneumophila from mature drinking water biofilms grown on copper versus unplasticized polyvinylchloride coupons
Citation:
Buse, H., J. Lu, I. Struewing, AND N. Ashbolt. Preferential colonization and release of Legionella pneumophila from mature drinking water biofilms grown on copper versus unplasticized polyvinylchloride coupons. INTERNATIONAL JOURNAL OF HYGIENE AND ENVIRONMENTAL HEALTH. Urban & Fischer Verlag Jena, Jena, Germany, 217(2):219-225, (2014).
Impact/Purpose:
To study the possible difference in Legionella colonization of premise plumbing (copper vs PVC pipe) with mature biofilms grown in drinking water.
Description:
Legionella persistence and amplification in premise drinking water systems is a known contributor to legionellosis outbreaks, especially in the presence of suitable eukaryotic hosts. Here we examined Legionella pneumophila behavior within drinking water biofilms grown on copper (Cu) and polyvinylchloride (PVC) surfaces in the presence of Acanthamoeba polyphaga, a well-studied L. pneumophila amoeba host. One year-old drinking water biofilms were established with dechlorinated tap water in six CDC biofilm reactors: three each containing Cu or PVC coupons. The biofilms were then inoculated with 4 x 108 L. pneumophila (PVC-Lp and Cu-Lp), or 4 x 108 L. pneumophila and 2 x 105 cells of A. polyphaga (PVC-Lp/Ap and Cu-Lp/Ap) and recirculated for 24 h before returning to a continuous flow condition, and compared to sterile water inoculated controls (PVC- and Cu-Control) over a 4 mo period. Within biofilms, L. pneumophila appeared more persistent by qPCR within Cu biofilms in the presence of A. polyphaga compared to PVC biofilms with or without A. polyphaga. However, L. pneumophila maintained their cultivability on PVC surfaces compared to below detectable CFUs from Cu surfaces (except for one occasion, day 32). L. pneumophila cells shed in the reactor effluent water also reflected persistent colonization of L. pneumophila within Cu-coupon reactors compared to PVC-coupon reactors when assayed by qPCR (at or <200 cell equivalents [CE] 100 mL-1from the PVC reactors days 84-119 vs 200-2,500 CE 100 mL-1 for the Cu-Lp and Cu-Lp/Ap reactors). In contrast to biofilm samples, effluent samples from inoculated Cu reactors contained more culturable L. pneumophila than PVC inoculated reactors, all of which supports the observation that L. pneumophila can colonize Cu surfaces more effectively than PVC and can be shed from the biofilms at a greater frequency and duration compared to L. pneumophila colonized PVC surfaces. Collectively, these results suggest that L. pneumophila colonization within and shed from biofilms grown on common in-premise plumbing materials differ greatly and may have an impact on subsequent human exposure to this opportunistic pathogen.
