Impact of Non-Legionella Bacteria on the Uptake and Intracellular Replication of Legionella pneumophila in Acanthamoeba castellanii and Naegleria lovaniensis |
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Authors: | P Declerck J Behets Y Delaedt A Margineanu E Lammertyn F Ollevier |
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Institution: | (1) Laboratory of Aquatic Ecology, Zoological Institute, Katholieke Universiteit Leuven, Charles De Bériotstraat 32, 3000 Louvain, Belgium;(2) Laboratory of Photochemistry and Spectroscopy, Dept. of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Louvain, Belgium;(3) Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Louvain, Belgium |
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Abstract: | In aquatic environments, Legionella pneumophila survives, in association with other bacteria, within biofilms by multiplying in free-living amoebae. The precise mechanisms
underlying several aspects of the uptake and intracellular replication of L. pneumophila in amoebae, especially in the presence of other bacteria, remain unknown. In the present study, we examined the competitive
effect of selected non-Legionella bacteria (Escherichia coli, Aeromonas hydrophila, Flavobacterium breve, and Pseudomonas aeruginosa) on the uptake of L. pneumophila serogroup 1 by the amoebae Acanthamoeba castellanii and Naegleria lovaniensis. We also investigated their possible influence on the intracellular replication of L. pneumophila in both amoeba species. Our results showed that the non-Legionella bacteria did not compete with L. pneumophila for uptake, suggesting that the amoeba hosts took in L. pneumophila through a specific and presumably highly efficient uptake mechanism. Living and heat-inactivated P. aeruginosa best supported the replication of L. pneumophila in N. lovaniensis and A. castellanii, respectively, whereas for both amoeba species, E. coli yielded the lowest number of replicated L. pneumophila. Furthermore, microscopic examination showed that 100% of the A. castellanii and only 2% of the N. lovaniensis population were infected with L. pneumophila at the end of the experiment. This study clearly shows the influence of some non-Legionella bacteria on the intracellular replication of L. pneumophila in A. castellanii and N. lovaniensis. It also demonstrates the different abilities of the two tested amoeba species to serve as a proper host for the replication
and distribution of the human pathogen in man-made aquatic environments such as cooling towers, shower heads, and air conditioning
systems with potential serious consequences for human health. |
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