Permissiveness of freshly isolated environmental strains of amoebae for growth ofLegionella pneumophila

Abstract

Legionella pneumophila is a pathogenic bacterium commonly found in water and responsible for severe pneumonia. Free-living amoebae are protozoa also found in water, which feed on bacteria by phagocytosis. Under favorable conditions, some L. pneumophila are able to resist phagocytic digestion and even multiply within amoebae. However, it is not clear whether L. pneumophila could infect at a same rate a large range of amoebae or if there is some selectivity towards specific amoebal genera or strains. Also, most studies have been performed using collection strains and not with freshly isolated strains. In our study, we assess the permissiveness of freshly isolated environmental strains of amoebae, belonging to three common genera (i.e. Acanthamoeba, Naegleria and Vermamoeba), for growth of L. pneumophila at three different temperatures. Our results indicated that all the tested strains of amoebae were permissive to L. pneumophila Lens and that there was no significant difference between the strains. Intracellular proliferation was more efficient at a temperature of 40°C. In conclusion, our work suggests that, under favorable conditions, virulent strains of L. pneumophila could equally infect a large number of isolates of common freshwater amoeba genera.

Intracellular Behaviour of Three Legionella pneumophila Strains within Three Amoeba Strains, Including Willaertia magna C2c Maky

“…Dupuy et al assessed the ability of 12 amoeba strains of Naegleria sp., Acanthamoeba sp., and Vermamoeba sp. to support the multiplication of L. pneumophila Lens at various temperatures (25 • C, 30 • C and 40 • C), and they revealed a more efficient intracellular proliferation with increasing temperatures [33]. Additionally, we did not observe the same behaviour according to the different bacteria and amoeba strains used during our experiments.…”

Annual variations and effects of temperature on Legionella spp. and other potential opportunistic pathogens in a bathroom

“…Legionella spp. appear ubiquitous in drinking water and building plumbing systems, albeit at generally very low concentrations, where they survive and some strains at least replicate inside several species of amoeba that colonize biofilms (Brooks et al 2004, Dupuy et al 2016, Fields et al 2002. However, unlike Legionella in cooling tower biofilms, where Legionella densities reached up to 10 5 cell L −1 at near optimal temperatures of ~35°C (Ikedo &Yabuuchi 1986, Yamamoto et al 1992, they are normally in low densities to nondetectable in drinking water (< 10 3 CFU or cell L −1 ).…”

Impact of drinking water treatment and distribution on the microbiome continuum: an ecological disturbance's perspective

“…Viewing the drinking water treatment systems from an ecological disturbance's perspective can provide practical guidance on the management of the microbial community in this oligotrophic environment. Important questions that can be asked include whether the microbial community is overly stressed with disinfectants in comparison with systems from some European countries, where natural filtration systems are used without the addition of a residual concentrations of disinfectants (Rosario-Ortiz et al, 2016); or whether nutrient control within the European systems is insufficient, allowing pathogens like Legionella pneumophila to have the opportunity to flourish within amoebae that are probably the only place in the system which meets their nutritional requirements (Breiman et al, 1990;Dupuy et al, 2016).…”