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Ecologie de Legionella pneumophila dans les réseaux de distribution d'eau potable

Abstract : Since it has been isolated in 1977, pneumonia epidemics involving Legionella pneumophila (Lp) are in constant progress. Contamination essentially occurs by inhalation of water droplets generated from water distribution networks. The ecology of Lp is complex, this bacteria growths inside protozoa and can persist in biofilms in the viable but not cultivable state.
The objective of this work was to understand better this ecology. Incubators allowing the sampling of biofilm were installed in situ in an internal network; the colonization in cold and in warm water was followed during 1 year. A pilot unit reproducing an internal network allowed comparing the efficiency of various disinfection treatments. Finally, the search for auto-inducers molecules that could explain the exacerbation of the virulence during the intracellular growth was led in various conditions.
Incubators allowed the detection of L. pneumophila by culture in cold water and resulted in a stabilization of the population in warm water. The use of specific probes did not allow improving the detection in biofilms.
During the disinfection assays with the pilot unit, the populations of biofilms were analyzed with molecular tools (FISH, viability staining) and by cultivation. Classification of treatments in order of efficiency is as follow: chlorine dioxide > chlorine > ozone > monochloramine > copper-silver. Only the chlorine dioxide has a residual activity in the dead leg flushed daily with treated water. Amoebae resist to treatments, and Lp returns to its initial level of population a few days only after their interruption.
Finally, we could not detect any auto-inducer molecule, and the incubation of Lp with these molecules does not seem to modify the invasion of amoebae.
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https://tel.archives-ouvertes.fr/tel-00116971
Contributor : Vincent Thomas <>
Submitted on : Wednesday, November 29, 2006 - 10:33:49 AM
Last modification on : Wednesday, September 16, 2020 - 5:04:14 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 7:07:08 PM

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  • HAL Id : tel-00116971, version 1

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Vincent Thomas. Ecologie de Legionella pneumophila dans les réseaux de distribution d'eau potable. Ecologie, Environnement. Université Paris Sud - Paris XI, 2004. Français. ⟨tel-00116971⟩

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