Bacterial Antagonistic Species of the Pathogenic Genus Legionella Isolated from Cooling Tower.

Kiran Paranjape,Simon Lévesque,Sébastien P Faucher

doi:10.3390/microorganisms10020392

Abstract

Legionella pneumophila is the causative agent of Legionnaires’ disease, a severe pneumonia. Cooling towers are a major source of large outbreaks of the disease. The growth of L. pneumophila in these habitats is influenced by the resident microbiota. Consequently, the aim of this study was to isolate and characterize bacterial species from cooling towers capable of inhibiting several strains of L. pneumophila and one strain of L. quinlivanii. Two cooling towers were sampled to isolate inhibiting bacterial species. Seven inhibitory isolates were isolated, through serial dilution plating and streaking on agar plates, belonging to seven distinct species. The genomes of these isolates were sequenced to identify potential genetic elements that could explain the inhibitory effect. The results showed that the bacterial isolates were taxonomically diverse and that one of the isolates may be a novel species. Genome analysis showed a high diversity of antimicrobial gene products identified in the genomes of the bacterial isolates. Finally, testing different strains of Legionella demonstrated varying degrees of susceptibility to the antimicrobial activity of the antagonistic species. This may be due to genetic variability between the Legionella strains. The results demonstrate that though cooling towers are breeding grounds for L. pneumophila, the bacteria must contend with various antagonistic species. Potentially, these species could be used to create an inhospitable environment for L. pneumophila, and thus decrease the probability of outbreaks occurring.

Highlights

Publisher’s Note: MDPI stays neutralLegionella pneumophila is the causative agent of Legionnaires’ disease, a severe and potentially fatal pneumonia
This organism is an aquatic bacterium ubiquitously found in engineered water systems (EWS) where it can colonize, survive, and grow
Seven bacterial colonies inhibiting L. pneumophila growth on plates were isolated from cooling towers and a model cooling tower

Summary

Introduction

Legionella pneumophila is the causative agent of Legionnaires’ disease, a severe and potentially fatal pneumonia. This organism is an aquatic bacterium ubiquitously found in engineered water systems (EWS) where it can colonize, survive, and grow. Examples of EWS that are known sources of L. pneumophila include water distribution systems, cooling towers, water reservoirs, misters, shower heads, and water faucets [1]. These systems usually produce aerosols that can be inhaled by people in their vicinity. The number of cases of Legionnaires’ disease has been on the rise in recent years. The number of cases of Legionnaires’ disease is believed to be underreported due to the lack of a common definition of the disease, efficient diagnostic with regard to jurisdictional claims in published maps and institutional affiliations

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