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

Jean-Marc Berjeaud,Margot Schlusselhuber,Emilie Portier,Julien Verdon,Clémence Loiseau,Willy Aucher,Olivier Lesouhaitier,Sylvie Chevalier

doi:10.3389/fmicb.2016.00486

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.

Highlights

Legionella pneumophila is a Gram-negative opportunistic intracellular human pathogen that is responsible for severe pneumonia called Legionnaires’ disease (LD; Fields et al, 2002)
For a few years some studies have highlighted natural compounds with anti-Legionella properties. Why such an interest? Probably because (i) L. pneumophila is a waterborne bacterium ubiquitously found in freshwater environments, (ii) LD is a severe and sometimes fatal multisystem illness involving atypical pneumonia, (iii) the development of manmade water systems such as air-conditioners and cooling towers has expanded the environmental niche of L. pneumophila in association with amoebae, (iv) emerging pathogens such as L. pneumophila or spore-forming bacteria such as Bacillus are able to resist to currently used water disinfection procedures, and (v) more efforts are needed to control disinfection by-products and minimize people exposure to potentially hazardous chemicals (Trihalomethanes, Haloacetic acids. . .) while maintaining adequate disinfection and control of targeted pathogens while respecting the environment
Legionella pneumophila appears sensitive to various biomolecules including molecules that are poorly active against others bacteria like surfactin

Summary

INTRODUCTION

Legionella pneumophila is a Gram-negative opportunistic intracellular human pathogen that is responsible for severe pneumonia called Legionnaires’ disease (LD; Fields et al, 2002). Because (i) L. pneumophila is a waterborne bacterium ubiquitously found in freshwater environments, (ii) LD is a severe and sometimes fatal multisystem illness involving atypical pneumonia, (iii) the development of manmade water systems such as air-conditioners and cooling towers has expanded the environmental niche of L. pneumophila in association with amoebae, (iv) emerging pathogens such as L. pneumophila or spore-forming bacteria such as Bacillus are able to resist to currently used water disinfection procedures, and (v) more efforts are needed to control disinfection by-products and minimize people exposure to potentially hazardous chemicals This structure was further confirmed for warnericin RK by circular dichroism (CD)

Producing bacteria

Thymus vulgaris

Findings

CONCLUSION