TY - JOUR

T1 - Temperature-driven growth of Legionella in lab-scale activated sludge systems and interaction with protozoa

AU - Caicedo, C.

AU - Rosenwinkel, K. H.

AU - Nogueira, R.

N1 - Funding Information: We thank Mrs. Karen Kock and Dr.-Ing. Corinna Lorey, from the Institute for Sanitary Engineering and Waste Management, Leibniz University Hannover, for valuable technical support in implementing and performing the qPCR and FISH/microscopy analyses, respectively. We would like also to thank Dr.-Ing. Katharina Ulbricht and Mr. Benjamin Schwanda for their support during the experimental phase. The financial support from the Ministry for Climate Protection, Environment, Agriculture, Conservation and Consumer Protection of the State of North Rhine-Westphalia (P 03/13-71 Ar) and the Ruhrverband (Essen) is acknowledged.

PY - 2018/3

Y1 - 2018/3

N2 - The occurrence of Legionella pneumophila in activated sludge systems has been reported in the literature. However, the factors triggering its growth are not yet well understood. This knowledge is needed to develop strategies to minimize the risk of the spread of Legionnaires’ disease that originates in these systems. In the present study, L. pneumophila multiplied exponentially at 35 °C in activated sludge, but lower temperatures (24 °C and 15 °C) did not favour the growth of the pathogen despite the presence of its protozoan hosts (free-living amoeba and ciliates). L. non-pneumophila species, which are adapted to low temperature, prevailed at 15 °C. Legionella was found dispersed in the activated sludge, forming clusters of different sizes and also inside protozoa. This study shows that temperature is a key parameter triggering the growth of L. pneumophila in activated sludge. The detection of infected protozoa suggests that these are important vehicles for the multiplication of Legionella. However, in this study it was not possible to exclude the growth of Legionella directly on the substrate or on the activated sludge matrix.

AB - The occurrence of Legionella pneumophila in activated sludge systems has been reported in the literature. However, the factors triggering its growth are not yet well understood. This knowledge is needed to develop strategies to minimize the risk of the spread of Legionnaires’ disease that originates in these systems. In the present study, L. pneumophila multiplied exponentially at 35 °C in activated sludge, but lower temperatures (24 °C and 15 °C) did not favour the growth of the pathogen despite the presence of its protozoan hosts (free-living amoeba and ciliates). L. non-pneumophila species, which are adapted to low temperature, prevailed at 15 °C. Legionella was found dispersed in the activated sludge, forming clusters of different sizes and also inside protozoa. This study shows that temperature is a key parameter triggering the growth of L. pneumophila in activated sludge. The detection of infected protozoa suggests that these are important vehicles for the multiplication of Legionella. However, in this study it was not possible to exclude the growth of Legionella directly on the substrate or on the activated sludge matrix.

KW - Activated sludge

KW - Free-living amoeba

KW - Legionella pneumophila

KW - Temperature

UR - http://www.scopus.com/inward/record.url?scp=85039742609&partnerID=8YFLogxK

U2 - 10.1016/j.ijheh.2017.12.003

DO - 10.1016/j.ijheh.2017.12.003

M3 - Article

C2 - 29279237

AN - SCOPUS:85039742609

VL - 221

SP - 315

EP - 322

JO - International Journal of Hygiene and Environmental Health

JF - International Journal of Hygiene and Environmental Health

SN - 1438-4639

IS - 2

ER -