title: Free-living amoebae and their associated bacteria in Austrian cooling towers: a 1-year routine screening.
abstract: Free-living amoebae (FLA) are widely spread in the environment and known to cause rare but often serious infections. Besides this, FLA may serve as vehicles for bacterial pathogens. In particular, Legionella pneumophila is known to replicate within FLA thereby also gaining enhanced infectivity. Cooling towers have been the source of outbreaks of Legionnaires' disease in the past and are thus usually screened for legionellae on a routine basis, not considering, however, FLA and their vehicle function. The aim of this study was to incorporate a screening system for host amoebae into a Legionella routine screening. A new real-time PCR-based screening system for various groups of FLA was established. Three cooling towers were screened every 2 weeks over the period of 1 year for FLA and Legionella spp., by culture and molecular methods in parallel. Altogether, 83.3 % of the cooling tower samples were positive for FLA, Acanthamoeba being the dominating genus. Interestingly, 69.7 % of the cooling tower samples were not suitable for the standard Legionella screening due to their high organic burden. In the remaining samples, positivity for Legionella spp. was 25 % by culture, but overall positivity was 50 % by molecular methods. Several amoebal isolates revealed intracellular bacteria.
authors.affiliation: Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Ute
authors.initials: U
authors.lastname: Scheikl
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria.
authors.forename: Han-Fei
authors.initials: HF
authors.lastname: Tsao
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Horn
authors.affiliation: Department of Mycobacteriology and Clinical Molecular Biology, AGES, Vienna, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Indra
authors.affiliation: Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria. julia.walochnik@meduniwien.ac.at.
authors.forename: Julia
authors.initials: J
authors.lastname: Walochnik
mesh_terms: D000656:Amoeba / Q000145:classification / Q000382:microbiology*; D001317:Austria; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D004196:Disease Outbreaks; D005618:Fresh Water / Q000382:microbiology* / Q000469:parasitology*
keywords: Acanthamoeba; Cooling towers; Free-living amoebae; Legionella; Real-time PCR; Screening