Legionella pneumophila: The Paradox of a Highly Sensitive Opportunistic Waterborne Pathogen Able to Persist in the Environment

Abstract

Legionella pneumophila, the major causative agent of Legionnaires’ disease, is found in freshwater environments in close association with free-living amoebae and multispecies biofilms, leading to persistence, spread, biocide resistance, and elevated virulence of the bacterium. Indeed, legionellosis outbreaks are mainly due to the ability of this bacterium to colonize and persist in water facilities, despite harsh physical and chemical treatments. However, these treatments are not totally efficient and, after a lag period, L. pneumophila may be able to quickly re-colonize these systems. Several natural compounds (biosurfactants, antimicrobial peptides…) with anti-Legionella properties have recently been described in the literature, highlighting their specific activities against this pathogen. In this review, we first consider this hallmark of Legionella to resist killing, in regard to its biofilm or host-associated life style. Then, we focus more accurately on natural anti-Legionella molecules described so far, which could provide new eco-friendly and alternative ways to struggle against this important pathogen in plumbing.

Bioaugmentation for the treatment of waterborne pathogen contamination water

“…Surfactin (lipopeptide), a well-characterized biosurfactant acquired from Bacillus subtilis, was found active toward various Legionella species including the Lens strain (CIP 108286) (Loiseau et al, 2015). According to previous reports, L. pneumophila was found to be sensitive to a variety of membrane-active biomolecules (Berjeaud et al, 2016). Lipopeptides and rhamnolipids derived from Bacillus and Pseudomonas, respectively, might be a potent anti-Legionella compound.…”

Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Critical Review Part I Uptake into Host Cells

“…While chlorine is commonly used and known to be effective, the continuous and rising number of legionellosis outbreaks causes concern that chlorine is not effective enough in removing L. pneumophila from water distribution systems [116][117][118]. Considering the bacteria's ability to grow within and use biofilms as protection from chlorination, complete eradication cannot be achieved without elevated water temperatures (>60 • C) [119].…”

Legionella Survey in the Plumbing System of a Sparse Academic Campus: A Case Study at the University of Perugia

“…Nevertheless, the electrical boilers allowed higher hot-water temperatures to be achieved and maintained. A thermal disinfection of the contaminated boilers was thus implemented, raising and maintaining the water temperature above the level at which Legionella cells do not survive (>60 °C) [2,9]. This approach proved to be effective as Legionella was absent in the Campus No.…”

“…All the taps served by electrical boilers set at a temperature higher than 55 • C were free of Legionella, while contaminations were found only within the boilers that were shut-off or set below 45 • C, with the only exception of one tap where the hot-water temperature was 53 • C. Nevertheless, the electrical boilers allowed higher hot-water temperatures to be achieved and maintained. A thermal disinfection of the contaminated boilers was thus implemented, raising and maintaining the water temperature above the level at which Legionella cells do not survive (>60 • C) [2,9]. This approach proved to be effective as Legionella was absent in the water samples taken in the following monitoring period ( Table 2).…”

“…The occurrence of Legionella contaminations in a building's tap water represents a serious health threat to end-users since it may infect human lungs, causing a form of atypical pneumonia called legionellosis or Legionnaires' disease [1,2]. The last available report, related to 2015, shows that in Europe 30 countries reported more than 6500 confirmed cases of legionellosis, corresponding to an overall rate of 14 per million inhabitants, with an increase over the 2011-2015 period [3].…”