Free-living amoebae and their intracellular pathogenic microorganisms: risks for water quality

Abstract

An increasing number of microorganisms, including bacteria but also viruses and eukaryotes, have been described as benefiting from interaction with free-living amoebae (FLA). Beneficial interaction can be due to resistance to predation conferring ecological advantage, intracellular survival and/or intracellular proliferation. This review highlights the potential risk associated with amoebae by listing all known pathogenic microbial species for which growth and/or survival promotion by FLA (mainly Acanthamoeba spp.) has been demonstrated. It focuses on the susceptibility of amoebal and intra-amoebal bacteria to various categories of biocides, the known mechanisms of action of these biocides against trophozoites and cysts and the various methods used to demonstrate efficacy of treatments against FLA. Brief descriptions of FLA ecology and prevalence in domestic/institutional water systems and their intrinsic pathogenicity are also presented. The intention is to provide an informed opinion on the environmental risks associated with the presence of FLA and on the survival of cysts following biocidal treatments, while also highlighting the need to conduct research on the roles of amoebae in aquatic ecosystems.

The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

“…Human infection most often occurs via the inhalation of L. pneumophila-containing water droplets that are produced by man-made devices (Pagnier et al, 2009). The environmental persistence of L. pneumophila is dependent upon its ability to infect and grow in amoebae (Lau & Ashbolt, 2009;Taylor et al, 2009;Thomas et al, 2010). Legionella-laden amoebae or amoebal vesicles and cysts harbouring bacteria might also be part of the inoculum that precipitates lung infection (Berk et al, 1998;Brieland et al, 1997).…”

Co-occurrence of free-living protozoa and foodborne pathogens on dishcloths: Implications for food safety

“…In addition, they can also act as a protective niche or shelter for bacteria against harsh environmental conditions (Barker and Brown, 1994;King et al, 1988;Snelling et al, 2005), or even as training grounds and evolutionary cribs for foodborne pathogens (Molmeret et al, 2005), enhancing bacterial virulence and mediating bacterial gene transfer. This points toward a role of FLP in the epidemiology of foodborne pathogenic bacteria with significant implications for food safety and public health International Journal of Food Microbiology 191 (2014) [89][90][91][92][93][94][95][96] (Gourabathini et al, 2008;Greub and Raoult, 2004;Thomas et al, 2010;Vaerewijck et al, 2014).…”

Free living amoebae in water environment: health implications

“…È emerso che le amebe a vita libera presenti nelle reti idriche ospiterebbero microrganismi più frequentemente di quanto accada per quelle isolate da sorgenti idriche naturali. Delle 539 specie batteriche riconosciute al 2008 come patogene umane dall'Environmental Protection Agency, 102 (circa il 20%) sono state descritte in grado di sopravvivere e/o moltiplicarsi all'interno delle amebe (63). Tale numero è sicuramente sottostimato se si considerano una serie di fattori.…”